Pregnant Body Book

THETHE COMPLETECOMPLETE ILLUSTRATEDILLUSTRATED GUIDEGUIDE FROMFROM CONCEPTIONCONCEPTION TOTO BIRTHBIRTH

THE PREGNANT BODY BOOK

DR. SARAH BREWER SHAONI BHATTACHARYA DR. JUSTINE DAVIES DR. SHEENA MEREDITH DR. PENNY PRESTON

Editorial consultant DR. PAUL MORAN PROJECT EDITORS Joyce, Edwards,Nathan Joanna urne, melbo york, new london, EDITORS SalimaHirani,JanineMcCaffrey, US SENIOR ART EDITOR MaxinePedliham PROJECT ART EDITOR CONSULTANT Dr. L.Sterlacci Susan SENIOR EDITOR Peter Frances RESEARCHER Dr. Say Rebecca munich,dehli and Lara Maiklem,NikkiSims US EDITOR JillHamilton Miezan vanZyl Alison Gardner CONTENTS THE FEMALEREPRODUCTIVE CYCLE FEMALE PUBERTY THE BREASTS CERVIX, ANDVAGINATHE UTERUS, THE OVARIES ANDFALLOPIAN TUBES THE FEMALEREPRODUCTIVE SYSTEM HOW SPERMISMADE MALE PUBERTY THE PROSTATE GLAND, PENIS, THE MALEREPRODUCTIVE SYSTEM BODY SYSTEMS ANATOMY GOING INSIDE IMAGING TECHNIQUES MEDICAL ADVANCES THE EVOLUTION OFPREGNANCY HUMAN PREGNANCY AND TESTES PICTURE RESEARCHERS MANAGING ART EDITOR MichelleBaxter PRODUCTION CONTROLLER DESIGN ASSISTANT PRODUCTION EDITOR ASSOCIATE PUBLISHER MANAGING EDITOR SarahLarter ART DIRECTOR Jonathan Metcalf PUBLISHER Jonathan Clare Joyce, DuncanTurnerClare DESIGNERS Hilary Bird Hilary INDEXER Karen VanRoss Riccie Janus, Phil Ormerod Fiona Macdonald Fiona Myriam Mégharbi, Mégharbi, Myriam Tony Phipps Liz Wheeler Erika Pepe 31 24 40 28 26 44 30 36 34 42 32 43 10 14 12 8

6 SENIOR 3DARTISTS or AMD processor; soundcard; 24-bit color display; soundcard; 24-bitcolordisplay; processor; or AMD KEY DEVELOPMENTS: MOTHER MOTHER ANDEMBRYO WEEKS 1–4 MONTH 1 TRIMESTER 1 CONCEPTION TO BIRTH BIRTH CONTROL THE ACT OFSEX DESIRE ANDAROUSAL ATTRACTIVENESS THE EVOLUTION OFSEX THE SCIENCE OFSEX PATTERNS OFINHERITANCE HOW DNAWORKS THE MOLECULESOFLIFE GENETICS MOTHER ANDEMBRYO WEEKS 5–8 MONTH 2 DIET ANDEXERCISE INPREGNANCY SAFETY EMBRYONIC DEVELOPMENT FERTILIZATION TO IMPLANTATION CONCEPTION INVESTIGATIONS GENETIC PROBLEMS AND or Intel processor; soundcard; 24-bit color display; soundcard; 24-bitcolordisplay; or Intelprocessor; DVD minimumsystemrequirements CREATIVE DIRECTOR PC: Mac OS Xv10.4;G4,G5, Macintosh: MacOS Peter BullArtStudio, AntbitsLtd Windows Vista,orWindows 7:Intel Windows XP with service pack 2, withservicepack Windows XP ADDITIONAL ILLUSTRATORS screen resolution1,024 x768 screen resolution1,024x768 3D ARTIST Gavin Whelan

ILLUSTRATORS Rajeev Doshi, ArranLewis Rajeev Doshi,

Rajeev Doshi

46 56 70 72 80 88 90 68 86 66 84 48 92 64 94 50 58 74 78 54 62 92 76 74 52

KEY DEVELOPMENTS: MOTHER 96 TRIMESTER 3 154 POSTNATAL 204 KEY DEVELOPMENTS: EMBRYO 98 MONTH 7 156 DEVELOPMENT MONTH 3 106 WEEKS 27–30 156 RECOVERY AND FEEDING 206 WEEKS 9–12 106 MOTHER AND FETUS 158 THE NEWBORN BABY 208 MOTHER AND FETUS 108 KEY DEVELOPMENTS: MOTHER 160 EARLY RESPONSES AND PROGRESS 210 KEY DEVELOPMENTS: MOTHER 110 KEY DEVELOPMENTS: FETUS 161 THE FIRST TWO YEARS 212 KEY DEVELOPMENTS: FETUS 114 MONTH 8 164 THE SKELETON 118 WEEKS 31–35 166 DISORDERS 214 MOTHER AND FETUS 166 FERTILITY DISORDERS 216 TRIMESTER 2 124 KEY DEVELOPMENTS: MOTHER 168 FEMALE REPRODUCTIVE DISORDERS 218 MONTH 4 126 KEY DEVELOPMENTS: FETUS 169 MALE REPRODUCTIVE DISORDERS 222 WEEKS 13–16 126 MONTH 9 170 SEXUALLY TRANSMITTED 224 DISEASES MOTHER AND FETUS 128 WEEKS 36–40 170 COMPLICATIONS IN PREGNANCY 226 KEY DEVELOPMENTS: MOTHER 130 MOTHER AND FETUS 172 LABOR AND DELIVERY PROBLEMS 232 KEY DEVELOPMENTS: FETUS 131 KEY DEVELOPMENTS: MOTHER 174 PROBLEMS IN NEWBORNS 234 MONTH 5 134 THE FORMATION OF THE BRAIN 176 PROBLEMS AFFECTING THE 240 KEY DEVELOPMENTS: FETUS 180 WEEKS 17–21 134 MOTHER AFTER DELIVERY MOTHER AND FETUS 136 THE MOTHER’S CHANGING BODY 182 THE FETUS’S CHANGING BODY 184 KEY DEVELOPMENTS: MOTHER 138 GLOSSARY 244 KEY DEVELOPMENTS: FETUS 139 INDEX 250 LABOR 186 MONTH 6 144 ACKNOWLEDGMENTS 256 WEEKS 18–26 144 PREPARING FOR BIRTH 188 MOTHER AND FETUS 146 THE FIRST STAGE OF LABOR 190 KEY DEVELOPMENTS: MOTHER 148 THE BIRTH 192 KEY DEVELOPMENTS: FETUS 149 ALTERNATIVE BIRTHS 198 THE FORMATION OF THE 152 AFTER THE BIRTH 200 RESPIRATORY SYSTEM ASSISTED BIRTH 202

STATISTICAL SYMBOLS

CROWN–RUMP HEART RATE LENGTH

CROWN–HEEL The Pregnant Body Book provides information on a wide range of Published in Great Britain by Dorling Kindersley Ltd. BLOOD PRESSURE LENGTH medical topics, and every effort has been made to ensure that the information in this book is accurate. The book is not a substitute A catalog record for this book is available for medical advice, however, and you are advised always to consult BLOOD VOLUME WEIGHT from the Library of Congress a physician or other health professional on personal health matters.

ISBN 978-0-7566-7559-2 First American Edition, June 2011–179659 BODY SYSTEM SYMBOLS DK books are available at special discounts when purchased in bulk for sales promotions, premium, SKIN, HAIR, NAILS, Published in the United States by DK Publishing, SKELETAL SYSTEM AND TEETH fund-raising, or educational use. For details, contact: 375 Hudson Street, New York, New York 10014

11 12 13 14 15 10 9 8 7 6 5 4 3 2 1 LYMPHATIC SYSTEM DK Publishing Special Markets, MUSCULAR SYSTEM 375 Hudson Street, Copyright © 2011 Dorling Kindersley Limited New York 10014 NERVOUS SYSTEM DIGESTIVE SYSTEM All rights reserved. or Without limiting the rights under copyright reserved above, no [email protected] ENDOCRINE SYSTEM URINARY SYSTEM part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means CARDIOVASCULAR REPRODUCTIVE Printed and bound in China by Hung Hing SYSTEM SYSTEM (electronic, mechanical, photocopying, recording, or otherwise), without prior written permission of the copyright owner and the above publisher of this book. Discover more at www.dk.com RESPIRATORY SYSTEM Just one of the millions of human sperm released By seven weeks, most of the structures, organs, and By 14 weeks, the fetus’s facial features can be seen, will penetrate one egg to create a new life. limbs have already developed in the human fetus. although its head is disproportionately large. HUMAN PREGNANCY The growth of a new life inside a woman’s uterus for the nine months of pregnancy is a truly amazing feat of biology. The creation of life is incredibly complex, and although each pregnancy is unique, some 130 million women worldwide experience its joys and risks each year.

The human body is capable of many astonishing things. But one of increases by 20 percent by the third trimester—an extra 15 beats its most intricate, complex, and profound achievements is the ability per minute. Even parts of her immune system will be suppressed to conceive, carry for nine months, and give birth to our helpless yet so her body does not reject the fetus as “foreign.” incredibly formed babies. As well as holding the promise of new life, pregnancy involves so many radical changes that it is little wonder Making babies that we marvel at and cherish the birth of children. Despite modern There is more than one way to have a baby. And all living organisms, concerns about fertility, humans are remarkably fecund. By 2050 we including humans, have evolved to follow one of two strategies. One will have reached a global population of 11 billion if we continue way to is to reproduce in great numbers, and have lots of offspring having children at the present rate. at the same time—this is called “big bang” reproduction. Having lots A pregnant woman’s body adapts in many amazing ways to of babies is extremely energy consuming, and organisms that follow accommodate and nurture the new life growing inside her. Her this strategy may breed just once and then die, such as Paciﬁc ligaments relax and stretch to allow space for her womb to grow, salmon, some butterﬂies, and some spiders. Many of their offspring and her pelvic joints soften for birth. Her uterus expands from the may perish, but because of their huge numbers, others will survive. size of a small pear to that of a watermelon by the end of pregnancy. The second, less spectacular strategy, is to have only a few babies She produces about 50 percent more blood so there is enough to over a lifetime, but to invest more in each one so each individual is pump around to the uterus and supply the growing fetus with a more likely to survive. This is the strategy that humans follow. It continuous supply of oxygen and nutrients, and her heart rate allows us to bear high-quality babies that thrive with parental care.

A male Emperor penguin incubates his egg and The marginated tortoise produces up to three A newborn Lemon shark emerges from its mother fasts while caring for his unborn offspring. clutches of between four and seven eggs a year. while remora ﬁsh break and eat the umbilical cord. At 20 weeks, the baby is now growing rapidly. Eyebrows, By 29 weeks, the baby’s face is starting to ﬁll out A healthy baby girl cries moments after being born. Her eyelashes, and hair will have grown by this stage. with fat as its rapid growth and weight gain continue. skin is covered in vernix, which protects against infection.

How other animals reproduce the young are ready to hatch, the animal will “give birth” to a clutch As humans we may take pregnancy for granted, but there are many of eggs, which will immediately spawn. Some fish and reptiles, such weird and wonderful ways in which to produce the next generation. as sharks and anacondas, employ this strategy of ovivipary. Some animals simply lay eggs, others carry eggs inside their bodies until they are ready to hatch, and many, like humans, go through Parental duties pregnancy and bear live young. Although we might think that only As soon as an embryo is conceived, the division of labor between birds and lower orders of animals lay eggs, there are even a few mother and father begins. In many species the mother bears the quirky mammals, such as the Duck-billed Platypus, that do so. burden of laying and guarding eggs, or pregnancy and birth, and Animals that lay eggs follow ovipary; oviparous animals include even raising the offspring. But males can have a crucial role. In some all birds, most reptiles, and most fish. The egg comprises yolk, which species, the male becomes “pregnant.” Male seahorses and pipefish contains all the embryo’s nourishment, and its protective shell and nurture fertilized eggs in brood pouches. The female deposits her layers keep the embryo safe inside. Often a parent has to keep eggs eggs in the male’s pouch, where they are fertilized by sperm. And the warm and protect them; many species incubate eggs until they hatch. male later “gives birth.” Male Emperor penguins also make devoted At the other end of the reproductive spectrum are those animals fathers, painstakingly incubating a single egg on their feet for nine that house, protect, warm, and nourish developing embryos inside weeks in freezing temperatures, allowing their mates to go and feed their own bodies. Humans, most other mammals, and a few rare after egg-laying. They, like many bird species, raise offspring together. reptiles, fish, amphibians, and scorpions, do this. This is known as Human children also thrive with both mother’s and father’s care, or vivipary. Humans and many other mammals are able to nurture other family support networks, because humans need a long, intense young inside the uterus thanks to a special organ that develops period of parenting. during pregnancy: the placenta. Not all viviparous animals have Some animals, such as kangaroos, can stop their pregnancies by this, and the placenta may have been pivotal in human evolution. stalling the embryo from implanting in the womb. The pregnancy But there are some animals that fall between egg-layers and can then be started weeks, or even a year, later. These animals have live-bearing animals—those whose embryos develop in eggs that evolved a way of bearing offspring when they can survive. Evolution remain within the animal’s body, somewhat like a pregnancy. When has honed pregnancy to give offspring the best chances possible.

The common Japanese male seahorse becomes Common Brushtail Possums, unlike most mammals, are not This four-day-old Japanese macaque reaches for its pregnant. The tiny seahorses are independent once born. nourished by a placenta but entirely on their mother’s milk. mother’s nipple, and it may nurse for up to 18 months. This color-enhanced MRI scan reveals the size This colored electron micrograph shows fetal tissues and some of the anatomical features of the brain (villi) that protrude into the placenta, allowing for the (shown in green) of a 36-week-old fetus. exchange of vital gasses, nutrients, and wastes. THE EVOLUTION OF PREGNANCY Pregnancy evolved in humans to allow for extended care of the growing fetus and enable us to have large-brained babies with astonishing learning capabilities. The female body has evolved to cope with and adapt to the challenges of carrying a fetus for nine months.

Pregnancy may be an amazing condition, but it is not without perils. period of care and level of nourishment; and the longer this period Why would humans evolve such a complex and risky way of lasts, the stronger the offspring are. Although a placenta is not reproducing when there are simpler methods available? The answer, essential for pregnancy (marsupials have a much simpler equivalent quite simply, is that pregnancy’s beneﬁts outweigh the negatives. organ), it helps considerably in giving human babies a head start. Carrying a fetus in the uterus for nine months ensures each aspect Crucially, a long pregnancy allows humans to bear large-brained of its environment is controlled: it is kept warm, safe, nourished, and babies. Large, complex brains, plus the ability to walk upright, makes supplied with oxygen. If we had evolved to lay eggs instead, as a humans special. Human brain volume is a massive 67–104 cubic handful of mammals do, the fetus would be limited to the supply of inches (1,100–1,700 cubic cm) compared with the 18–31 cubic inches nutrients contained in the yolk. Pregnancy allows us to extend the (300-500 cubic cm) of our closest living relative, the chimpanzee.

PREGNANCY FACTFILE

Pregnancy, birth, and newborns vary incredibly within the animal world. Human do not have a complex placenta, but then make up the difference with extended newborns are vulnerable compared with those of other mammals—wildebeest maternal care. Human babies require much parental care. In terms of motor, calves can run from predators within hours of birth, while bat babies can ﬂy chemical, and brain development, a human baby displays the same levels at within two to four weeks of birth. Marsupials have short pregnancies because they about nine months as those displayed by its primate cousins at birth.

HUMAN BLUE WILDEBEEST ELEPHANT RED KANGAROO MOUSE BAT

Gestation period 40 weeks 8 months 22 months 32–34 days 18–21 days 40 days to 8 months

Litter size 1 or 2 (very rarely more) 1 1 (rarely twins) 1 8–12 1 or 2 (3 or 4 in some species)

Average weight 6–9 lb (2.7–4.1 kg) 49 lb (22 kg) 198–265 lb (90–120 kg) 1⁄33 oz (0.75 g) 1⁄50–1⁄19 oz (0.5–1.5 g) 0–30 percent of mother’s body weight

Ability at birth Helpless: cannot hold up Can stand within Long period of Climbs into mother’s Helpless; no pigment Completely dependent own head; can focus eyes 15 minutes; can eat grass maternal care and pouch unaided within or hair; closed eyes and on mother for food and to see only 171⁄2 in (45 cm) within 10 days; weaned learning; weaned 3 minutes; leaves the ears. By 3 weeks, have protection, but mature ahead. Very long period of at nine months at 4–5 years pouch at 240 days but adult hair, open eyes, quickly and ﬂy within parental care required to suckles for another ears, and teeth and 2–4 weeks; weaned reach adulthood 3–4 months can be weaned shortly after

Time until next Can be within months, 1 year 4–6 years, Can get pregnant 1 day Can conceive within Generally breed once pregnancy although many depending on after birth but the hours of birth, but can a year but has various increase spacing female’s age pregnancy is paused delay pregnancy by up strategies to delay until a suckling joey to 10 days if still nursing pregnancy is 200 days old by halting implantation

8 This colored x-ray shows a woman’s pelvis is short and broad (an adaptation for child-bearing) and also has a narrow opening (adapted for walking upright).

Placenta Human babies also have proportionately gigantic heads. A newborn’s Provides fetus with nutrients and oxygen, brain is already a quarter of the size of an adult’s, making up about removes wastes and 10 percent of its body weight. In an adult, the brain makes up only carbon dioxide, and provides immunity about 2 percent of body weight. The life-sustaining organ Humans and other mammals may well owe their evolutionary and reproductive success to the placenta—a life-sustaining organ. Many scientists argue that we could not have developed large-brained young without it. The placenta enables a vital exchange between the blood of the mother and the fetus, passing nutrients and oxygen to the fetus, and passing wastes and carbon dioxide from the fetus’s system to the mother’s to be carried away. It also has an important immune function, because it acts as a barrier and allows some antibodies to pass from mother to fetus. In humans, the placenta burrows deep into the uterine wall, and recent studies suggest that this depth may give better access to the nourishing maternal blood supply and, therefore, help humans have large-brained babies. Many mammals benefit from the placenta even after birth, by consuming the nutritious organ. Some human cultures have also been known to eat the “afterbirth.” Why women are special Women’s bodies have been sculpted to bear children, but evolution has had to accommodate two opposing challenges in order to do this. Humans are special because of their large, complex brains and their ability to walk upright. But these two massive evolutionary advantages are also in direct conflict. A shorter, broader pelvis allows humans to walk upright. However, one side-effect of this is that the birth canal is no longer straight and wide, but curved and narrow. Although the birth canal is shorter, during Pelvis the final stage of labor the mother must not only push the baby’s head Narrow enough to allow Pubic symphysis downward but also upward as it passes part of the vertebral column upright walking, but with a large Enlarges during enough opening (pelvic inlet) Large head pregnancy, allowing called the pelvic curve. This conundrum has meant that women have for the head to pass through Encases a large brain; pelvis to be flexible evolved special pelvises that are wide enough for a large-brained baby must pass through during birth pelvic inlet during birth to pass through, but narrow enough for an upright lifestyle. The many demands on our bodies have been delicately balanced A SPECIALLY DESIGNED PELVIS Women have slightly shorter, broader pelvises by evolution. But amid these conflicts and compromises, child- than men to allow for the passage of babies’ bearing still has its dangers. Throughout the ages, humanity has sought heads. Unlike other primates, human babies are about the same size as the birth canal, resulting the best ways to bring its young into the world, and now, in the in complicated and painful labors. modern era, medicine can give nature a helping hand in many ways. 9 Ultrasound scanning of the abdomen offers A late MRI scan at 33 weeks reveals the placenta is A baby is extracted from its mother’s womb expectant parents a glimpse of their baby. blocking the cervix (placenta previa) in this woman. by surgeons performing a cesarean section. MEDICAL ADVANCES Thanks to modern medicine there has never been a safer time to be pregnant. Advances in care mean that mother and child are cushioned from pregnancy’s risks in most developed countries, and the situation is generally improving worldwide.

The care given to pregnant women during pregnancy and birth has Preconception care improved unrecognizably, such that it is easy to take for granted Because of improvements in our medical understanding, today many and forget how hazardous pregnancy and birth once were. Even a women may start preparing their bodies (eating a healthy diet and century ago, it was not unusual to see maternal death rates of 500 doing moderate exercise) before pregnancy to give their children the in every 100,000 women giving birth in countries such as the US best possible start. Many women now take folic acid supplements or the UK. Today, that figure is much lower, with between 4 and 17 before conception and in the first trimester, to protect against neural women per 100,000 dying in developed nations. tube defects, such as spina bifida, in the fetus. This sea-change is a result of improvements in medicine and the Couples planning a baby may adjust their lifestyles to improve quality of care, especially in the second half of the 20th century, their chances of conceiving. For example, in women, stopping alongside nutritional and socioeconomic improvements. Nevertheless, smoking and cutting down on alcohol, caffeine, and even stress are safety in pregnancy still needs to be improved internationally. In recommended. Men may also be advised to cut down on alcohol 2008 about 360,000 women died from pregnancy- or childbirth- and smoking because it can affect the quality of their sperm. related causes, mostly in the developing world. Globally, infant Advances mean that many women delay childbearing. A woman’s health has also massively improved, and the mortality rate in age (too young or too old) and the spacing between children (too close children under a year old is less than half of the mortality in 1960. together or too far apart) may impact on her and her child’s health.

TIMELINE

Medical advances gathered pace 1952 APGAR SCORING: 1960 FEMALE “PILL”: 1966 REAL TIME 1973 SCANNING 1975 HOME PREGNANCY

in the second half of the 20th An examination carried out within five The oral contraceptive pill ULTRASOUND: MEASUREMENTS: TEST INTRODUCED: minutes of birth, this assesses the newborn’s gave women unprecedented This revolutionized Measuring certain Available over the century. Notable advances before “Appearance, Pulse, Grimace, Activity, and control over their fertility, scanning as the fetus’s aspects of the fetus in counter, this test gives then include the first cesarean Respiration”, or its skin color, heart-rate, and has helped reduce motion and life could utero were used to instant results. section—performed from reflexes, muscle tone, and breathing. The unwanted pregnancies. be observed. give an indication of ancient times in India, Rome, score indicates any need for medical help. age, size, and weight. and Greece; the use of forceps to assist labor from the 17th century; the invention of the stethoscope 1960 1970 1950 1955 1965 1975 in 1895; and the use of antibiotics from the 1930s, which massively 1959 FETAL ULTRASOUND SCANNING: 1962 HEEL PRICK TEST: 1968 FETAL 1975 SCANNING FOR cut maternal death rates. High-frequency sound waves were This newborn blood test CARDIOTOCOGRAPH: SPINA BIFIDA: first used to measure a fetus’s head, checks for rare disorders, such Now, fetal heart rates could The first case of giving an idea of size and growth. as phenylketonuria, which can be monitored electronically ultrasound detection of benefit from early diagnosis to tell if a baby was in this neural tube defect, and treatment. distress during labor. leading to a termination of pregnancy.

10 Premature babies have much better survival rates Newborn measurements allow health professionals Hearing tests can catch problems early, since hearing now, thanks to expert care in special baby units to assess where a baby sits in the normal range. problems impact on speech and language development.

Advances in prenatal care Advances in perinatal care Care during pregnancy—the prenatal period—has improved incredibly The perinatal period runs from the 28th week of pregnancy to about in the modern age. Routine medical care is available in many four weeks after birth. This window is crucial to the well-being of countries. And leaps in technology, such as the invention of the mother and child. Advances such as the discovery of antibiotics and stethoscope and, more recently, ultrasound, mean that we can now better hygiene have slashed death rates for mothers in the last century. hear and see the fetus, which helps health professionals assess the Now childbirth and its immediate aftermath can be much safer. care needed in any particular pregnancy. Birth can be helped along—labor can be induced, assisted (for example, The mother’s health may be routinely monitored for conditions with forceps), or a cesarean section can be performed. Many types that may affect her unborn child. For example, urine will be tested of pain relief are available to women in many countries, along with regularly for urinary tract infections, which can lead to premature continuous monitoring of the fetus during labor, for signs of distress. labor. And blood may be screened for sexually transmitted diseases, which, left untreated, could be transmitted to the baby either in Advances in postnatal care utero or at birth, with harmful consequences. Blood tests may also Immediately after birth, a newborn undergoes physical tests to assess detect conditions such as anemia or gestational diabetes in the whether it needs medical intervention. Newborn survival and health mother, which can then be treated. Blood pressure monitoring can have been greatly improved by the availability of medicines and give warning of conditions such as preeclampsia. vaccines. Modern technology also gives premature babies a far Abnormalities may be spotted on an ultrasound scan or by tests greater chance of survival than they used to have. such as amniocentesis (in which amniotic ﬂuid from around the fetus Mothers and babies are often monitored for six weeks after birth. is sampled and tested for a chromosomal disorder). In some cases Health professionals will check both physical well-being (weigh the where there is a high risk of an inherited disorder, genetic tests may baby, give advice on feeding, and administer routine immunizations) be done. New techniques may also offer those facing genetic problems and emotional health (looking for signs of postpartum depression the option of selecting disease-free embryos for in-vitro fertilization. and strong bonding, and offering advice and support as necessary).

1978 FIRST 1989 EMBYRO SCREENING 1991 ICSI: 1992 SCREENING FOR DOWN SYNDROME: TEST-TUBE BABY: FOR GENETIC DISORDERS: This form of IVF, where a The first report of nuchal fold thickening— Louise Brown, in The first embryos were sperm is injected directly the area at the back of the neck—in Down the UK, became the screened and chosen for into an egg, gives hope to syndrome fetuses seen on ultrasound. first child to be implantation on the basis of infertile men. This formed the basis for the nuchal born after in-vitro being free of a disease gene. translucency test. fertilization (IVF). 2000 2005 2010 1980 1990 1995 1985

1990S FETAL DOPPLER: 1991: HIP CHECK: 2004 FIRST OVARIAN TRANSPLANT BABY: Advances in computing meant A newborn’s hips are checked for Frozen ovarian tissue, taken before cancer high-resolution images became available “clicky” joints, or developmental treatment, enables a woman to have a baby using the Doppler effect to measure dysplasia. Early treatment avoids seven years later. Such an advance opens movement such as blood ﬂow in the disability later in life. the door to the possibility of women in fetus and placenta. the future postponing childbearing without risking infertility.

11 IMAGING HOW ULTRASOUND WORKS Ultrasound harnesses high-frequency sound waves in the range of 2–18 megahertz. A hand-held probe TECHNIQUES called a transducer, which is pressed against the The ability to see, hear, and monitor skin, contains a crystal that transmits sound waves. the fetus in the uterus has been one The transducer also contains a microphone to record returning echoes as the waves bounce off of the most profound medical solid substances, such as organs or bone. The advances of the 20th century. It has echoes are then processed by a computer to IMAGING TECHNIQUES I IMAGING revolutionized prenatal care by generate a real-time 2D image. This safe, painless allowing health professionals to check procedure is widely used for routine prenatal checks. A similar technology, called Doppler the health of a fetus and placenta and ultrasound scanning, is used to look at moving assess the progress of a pregnancy. substances, such as blood ﬂow in the fetus or placenta. Recent

INTRODUCTION INTRODUCTION technological advances THE HISTORY OF ULTRASOUND USING A TRANSDUCER make it possible to use After gel has been rubbed over the Until a few decades ago, the only way of checking woman’s abdomen, the transducer is run ultrasound to build 3D a fetus’s growth or position was by palpating the with gentle pressure over the same area. images of fetuses too. abdomen of a pregnant woman. Since the 1940s, Microphone scientists had been investigating the use of This receives returning waves, whose high-frequency sound waves to look inside the SONIC PICTURE pitch and direction may have been changed by internal structures. body, and World War II may have acted as a Sound waves passing through the mother’s catalyst to their application to obstetrics. Ian abdomen bounce off the Point of contact Donald at Glasgow University was inspired by his fetus’s body as well as Gel between the other structures, such transducer and abdomen helps experiences in the British Royal Air Force. He took as the placenta and eliminate any the principles of sonar (which used sound waves amniotic sac. air pockets. Transducer to detect U-boats) and, with fellow obstetrician Applying electrical energy John McVicar and engineer Tom Brown, to a piezo-electric crystal inside the transducer made the ﬁrst ultrasound scanner to distorts its mechanical produce clinically useful 2D images. structure. It expands and contracts, emitting In 1958, the team published ultrasound waves. work describing how they used ultrasound to look at abdominal Sound waves The frequencies used masses in 100 patients. They for imaging are inaudible soon developed the technology to humans and have no known harmful effects to measure the fetus in the uterus, on the fetus or mother. which became routine procedure.

Uterus Ultrasound waves travel through this to give a picture of what lies inside.

DIASONOGRAPH Produced in 1963, this was one of the ﬁrst 20-week-old fetus commercial ultrasound machines. The Ultrasound scans can screen a fetus patient lay beneath it while a probe moved of this age for potential congenital horizontally and vertically above them. abnormalities in an “anomaly” scan. 12 Cable to computer 3D IMAGING and monitor The data is transmitted to a In recent years, striking, in-depth images of fetuses have been computer, where it is processed, and the resulting 2D scan image displayed by 3D scans. They are obtained by stitching together is displayed on a screen. a series of successive 2D shots or “slices” into a 3D image using modern computer technology. Some parents acquire 3D scan images commercially as souvenirs, but many medical organizations advise against such “keepsake” scans because of the concern that, should the scan unexpectedly reveal abnormalities in the fetus, the parents, being in a nonmedical situation, may not READING SCAN IMAGES have the appropriate support available. A 2D scan image shows contrasting black, white, and gray areas. These correspond to the type of structures that the MULTIPLE SCAN Transducer sound waves encounter as they pass through the body, and SLICES how these structures create echoes. When ultrasound waves A series of 2D “slices” or images Seen as white bounce off solid structures such as bone or muscle, they The fetus’s are combined produce a white or light gray image. But soft or empty areas, into a 3D image bones are white such as the eyes or chambers of the heart, will appear black. on the scan as by a process called surface they cause the Seen as black rendering. ultrasound waves Amniotic ﬂuid shows as black to echo back. because sound waves travel through it, so there is no echo.

Seen as gray Muscle appears as gray, as it bounces sound waves back.

20-week-old fetus

A FETUS IN 3D The third dimension, depth, enables us to see the shape of the fetus Nose more clearly. The soft parts of the FACIAL FEATURES nose cannot be seen, Eye but the bone structure A fetus’s face can be seen in an The soft tissue of the around it appears LOOKING INSIDE THE BODY ultrasound scan image. Even 2D eye appears black in white. scans can give clues to the fetus’s the scan image, while appearance by revealing some of the bone of the eye There are other imaging techniques that can be used to peer inside the body its facial features—for example, socket gives a white Mouth cavity before or during pregnancy. Laparoscopy, a surgical procedure, can be used to the shape of its face. outline. This is seen as black. investigate fertility by allowing doctors to examine the fallopian tubes, ovaries, and uterus. A fetoscopy may be performed to visualize the fetus, collect fetal tissue samples, and even to perform fetal surgery. To do this, a ﬁberoptic tube is Two heads inserted through the cervix or surgically through the abdomen. MRI scans may The white outlines of the also be carried out on pregnant women to investigate suspected problems, skulls indicate the two heads of twin fetuses. This scan although they are not advised in the ﬁrst trimester. image cannot reveal if they are identical or fraternal twins.

WHAT SCANS CAN TELL US SEEING WITH A scan reveals basic information about a pregnancy—the SOUND WAVES LAPAROSCOPIC VIEW FETOSCOPIC VIEW MRI SCAN sex, size, and age of the fetus, its position (and that of the By moving the transducer, the A flexible tube with a An endoscope is inserted Powerful magnetic fields placenta) in the uterus, and if it is a multiple pregnancy. camera and light source is into the uterus to examine and radio waves produce Scans can warn of potential problems, such as placenta sonographer can direct the ultrasound inserted through a cut in the fetus for diagnosis or a detailed image. Pregnant previa (in which the placenta blocks the cervix, the waves in order to the abdomen. Shots of the to take skin samples—for women are scanned fetus’s exit route), or growth problems in the fetus or reveal particular reproductive system are example, to test for only if the procedure is placenta. Screening for abnormalities is also an important views that provide then relayed to a screen. inherited diseases. considered to be essential. function of scanning. helpful information. 13 GOING INSIDE Modern technology, especially the use of new imaging techniques, has given an incredible window into how a new human life develops in the uterus. It is now possible to see, photograph, and even film a fetus in unprecedented detail.

It is difficult to believe that only just over 50 years ago there was no way of checking the growth of a fetus except by feeling, or palpating, a pregnant woman’s abdomen. The idea of actually being able to see a fetus rubbing its eye or sticking out its tongue was unimaginable. The development of obstetric ultrasound imaging in the late 1950s opened the door to a range of technological possibilities, and now not only is ultrasound imaging in pregnancy routine in many countries, but more detailed scanning is also possible. Ordinary two-dimensional ultrasound scans are often taken in the first trimester to date a pregnancy, and later, scans at around 20 weeks may be used to screen for various congenital problems, such as spina bifida or cleft palate. Even more detailed images can be obtained using three-dimensional ultrasound (including most of the images shown here) or MRI techniques, and movements such as blood flow in the placenta can be imaged using Doppler ultrasound. All of these techniques combine to offer powerful tools for monitoring and screening during pregnancy, and give the parents the chance to see their unborn baby.

14 GOING INSIDE

EXPRESSION Three-dimensional ultrasound pictures reveal a range of expressions on the face of this 38-week-old fetus as it rubs its eyes and face, opens its mouth, and sticks out its tongue. Images like this are possible due to an explosion in computing power, which has meant that flat, two-dimensional scans can now be “sewn together” digitally to give three-dimensional pictures that can reveal amazing details such as fingernails and facial features. A fetus’s face develops rapidly early in pregnancy, with tiny nostrils becoming visible and the lenses of the eyes forming by seven weeks, but it is not until the second trimester that the face takes on a humanlike appearance. By 16 weeks, the eyes have moved to the front of the face, and the ears are near their final positions. The fetus’s facial muscles are also more developed, with the result that facial expressions such as frowning or smiling may also be seen. 15 GOING INSIDE

FRONT VIEW OF FACE AT EIGHT MONTHS

EAR AT ABOUT 39 WEEKS SIDE VIEW OF FACE AT NINE MONTHS THE HEAD AND FACE The head and face start developing early in pregnancy, although initially development is relatively slow. Eye buds and the passageways that will become ears start developing on the side of the head at about the sixth week. By the tenth week, the head has become rounder and the neck has started to develop. In these early stages, the fetus is very top-heavy: at 11 weeks, for example, its head is half of its total body length. The second trimester is a period of rapid development for the head and face. This is when the eyes move to the front of the face (with the eyelids closed to protect the eyes), the ears move to their ﬁnal positions, and the facial muscles develop. By 22 weeks, the fetus’s eyebrows may be visible, and by 26 weeks it may have eyelashes. By 27 weeks, the eyes open and there is hair on the head. By the time the baby is born, its head is more in proportion to its body, although still as much as a quarter of its body length. THE POSTERIOR FONTANELLE FRONT VIEW OF FACE AT ABOUT 27 WEEKS 16 GOING INSIDE

SKELETON AT 16 WEEKS THE SKELETON The development of the fetus’s skeleton begins in the first trimester, although the process is not complete until long after birth. The top image shows the fetus at 16 weeks. Before then, the tissues that will eventually become bone are laid down in the correct places—for example, around the head or in the arms, legs, and fingers—and these tissues are then ossified to make bone. This process of ossification can happen in two ways. Where there are membranes—as around the fetus’s head—bone grows over the membranes to form bony plates. In other places, such as the limbs, ribs, and backbone, cartilage is gradually converted to bone from the middle outward. The image at the bottom right shows ossification in a 12-week-old fetus, with the partially ossified bones of the skull, arms, and ribcage shown in red. By 29 weeks (image at bottom left), the bones are fully developed, although SKELETON AT 29 WEEKS OSSIFICATION AT 12 WEEKS they are still soft. 17 GOING INSIDE

ARMS AND LEGS The arms and legs grow from tiny limb buds that appear at about six weeks. Paddlelike at first, the limbs grow longer, and within a couple of weeks the fingers start to form. Toes appear at about nine weeks—the image at the bottom right shows the toes of a 10-week-old fetus. At nine weeks, the arms may develop bones and can bend at the elbow, and by 14 weeks the arms may already be the length that they will be when the baby is born. Finer details such as fingerprints and footprints start forming around 23 weeks. By 25 weeks, the hands are fully developed, and the fetus may use them to explore inside the uterus. Fingernails and toenails grow in the late second and early third trimesters; the main image on this page shows the well-developed hands of a 23-week-old fetus. As pregnancy progresses, the limbs develop further, and the fetus may deliver lively punches and kicks in the third trimester. 18 GOING INSIDE

TWINS

TRIPLETS

MULTIPLE BIRTHS These three-dimensional ultrasound scans (near left) show twins, triplets, and quadruplets (from top to bottom). In the image of the triplets, a separate amniotic sac is clearly visible around each fetus. Between each amniotic sac, a small amount of placenta is seen to form a V-shape. This indicates that each of the triplets has a separate placenta. As a result of using such modern imaging techniques, medical professionals can not only discover whether a woman has a multiple pregnancy but can also gain valuable information about the state of the pregnancy. Multiple pregnancies are riskier than singleton ones, and scans can show, for example, whether fetuses share a placenta or amniotic sac, how each fetus is growing, and whether any of them is at particular risk. Such information can then be used to inform decisions, such as whether labor should QUADRUPLETS be induced early. 19 FROM CELL TO FETUS

The journey from embryo to fetus to baby begins with rapid the grape-sized embryo is termed a “fetus.” And by 12 weeks, the development in the ﬁrst trimester, followed by massive growth in fetus is fully formed. Its body grows rapidly in the second trimester, the second, and preparation for birth in the third. After conception, such that its head and body approach the proportions of an adult. the embryo divides into a growing ball of cells, which implants in By 14 weeks, its sex may be apparent. The brain grows rapidly in the uterine lining on about the sixth day. The cells differentiate into the last few weeks of the second trimester. By 30 weeks, in the third three layers, from which the fetus’s major body systems will arise. trimester, the fetus is becoming plump. In the run-up to birth, By the ﬁfth week of pregnancy, a spinal cord is forming, limb buds antibodies move into the fetus’s blood from the mother, the fetus’s are sprouting, and the organs are developing. From the tenth week, eyes open, its sexual organs mature, and its lungs practice dilating.

NON-PREGNANT UTERUS 6 WEEKS 7 WEEKS

11 WEEKS 12 WEEKS 13 WEEKS

20 FROM CELL TO FETUS

8 WEEKS 9 WEEKS 10 WEEKS

14 WEEKS 15 WEEKS 16 WEEKS

21 FROM CELL TO FETUS CELL TO FROM

17 WEEKS 18 WEEKS 19 WEEKS

22 WEEKS 24 WEEKS 26 WEEKS

22 FROM CELL TO FETUS

20 WEEKS

28 WEEKS 30 WEEKS

23 THE FEMALE AND MALE REPRODUCTIVE SYSTEMS CAN PRODUCE, STORE, AND BRING TOGETHER AN EGG AND A SPERM, GIVING THE POTENTIAL FOR A NEW LIFE. THE FEMALE SYSTEM IS ALSO ABLE TO NURTURE AND PROTECT THIS NEW INDIVIDUAL IN THE UTERUS FOR THE NINE MONTHS OF PREGNANCY, BEFORE DELIVERING IT INTO THE OUTSIDE WORLD AT BIRTH. FROM THEN ON, THE MOTHER CAN CONTINUE TO PROVIDE NOURISHMENT IN THE FORM OF BREAST MILK. ALL OF THESE PROCESSES TAKE PLACE AS A RESULT OF COMPLEX HORMONAL INTERACTIONS THAT TRIGGER THE BEGINNING OF THE REPRODUCTIVE PROCESS AT PUBERTY AND ENABLE IT TO CONTINUE THROUGHOUT THE FERTILE PART OF LIFE. ANATOMY BODY REPRODUCTIVE URINARY SYSTEMS SYSTEM SYSTEM Female and male reproductive This complex ﬁltration system The human body can be divided organs generate the egg and ﬁlters blood in the kidneys sperm to create new life. to eliminate waste products

BODY SYSTEMS I BODY into systems—groups of organs and The ovaries produce the and to maintain the body’s tissues that work together to carry hormones needed to delicate equilibrium. The prepare the uterus for resulting waste is stored out a specific function or functions. a fertilized egg. Once in the bladder as urine. During pregnancy, many of these a woman becomes Hormones control how ANATOMY ANATOMY pregnant, her system much urine is made systems alter their size, structure, undergoes dramatic before it is excreted changes: the uterus via the urethra. During and even their function to meet enlarges to fit the pregnancy, the kidneys the needs of the growing fetus. growing fetus; the lengthen by 3/8 in (1 cm) and placenta develops their blood flow increases Some of the changes are obvious, to connect fetal massively, which causes such as the rapidly expanding and maternal frequent urination even circulations; and before a developing fetus uterus and breasts. Other changes, the breasts prepare is large enough to press such as the massive increase in for lactation. on the bladder. blood volume, are more subtle yet essential for fetal well-being and a successful pregnancy.

MALE MALE

RESPIRATORY CARDIOVASCULAR LYMPHATIC AND SYSTEM SYSTEM IMMUNE SYSTEM The muscular diaphragm The heart works relentlessly to The lymphatic system diverts contracts and relaxes to bring pump blood around the body excess tissue fluid back into air via the nose and trachea in a complex system of blood the blood. The expanding into the lungs and out again. vessels (arteries, arterioles, uterus can press on blood Within the lungs, oxygen capillaries, venules, and vessels within the pelvis, from the air diffuses into veins) that supply every resulting in a buildup the blood, while carbon tissue and organ. During of fluid in body tissues dioxide diffuses out of pregnancy, the volume (edema), commonly the blood and into the of blood circulating those of the legs and lungs, ready for exhalation. increases by up to feet. The immune This gaseous exchange is 50 percent to supply system protects the vital for all body tissues. the growing fetus with body from infections Oxygen consumption rises everything it needs. and foreign invaders. slowly in pregnancy, reaching Pumping more blood Pregnant women an increase of 20 percent is extra work for appear to be at full term. A woman’s the heart, so it susceptible to breathing rate rises to about contracts more picking up colds 18 breaths a minute, up from forcefully and and other common 12–15. During labor, oxygen more frequently; infections, but this consumption may rise up to the heart rate rises may be due to the 60 percent, a reflection of by up to 15 beats increased blood flow the physical work involved. per minute. in mucus membranes.

26 BODY SYSTEMS

NERVOUS DIGESTIVE ENDOCRINE SYSTEM SYSTEM SYSTEM The brain, spinal cord, and a Essentially, one long tube from This system of glands network of nerves around mouth to anus (including the produces myriad hormones

the body continue to esophagus, stomach, and that maintain the body’s I ANATOMY control the actions of intestines), the digestive equilibrium. Many hormonal the body and respond system breaks down food changes occur at certain to what is happening. so that nutrients can be stages of a pregnancy. For During pregnancy, the absorbed and waste example, one part of the female sex hormone products expelled. pituitary gland releases progesterone directly Accessory organs, such oxytocin, needed to affects the brain’s as the liver, pancreas, initiate labor, and another respiratory center to and gallbladder, provide part releases prolactin, increase its sensitivity biochemical help. During needed for milk production. to carbon dioxide, pregnancy, hormonal The placenta not only forms thereby raising the changes slow contractions a connection between fetal breathing rate to that propel food and waste and maternal circulations, it “blow off” more through the intestines, also acts as an endocrine carbon dioxide. so constipation can occur. gland itself, producing Certain conditions The valve between the estrogen and progesterone affecting nerves, such esophagus and stomach to sustain pregnancy. as sciatica, may be more may be more relaxed, likely during pregnancy. resulting in heartburn.

MALE

SKELETAL MUSCULAR SKIN, HAIR SYSTEM SYSTEM AND NAILS The bones provide a moving The muscles enable the bones The skin is the body’s largest framework for the body. of the skeleton to move. organ, measuring some During pregnancy, the With the ligaments and 211/2 square ft (2 sq m), hormones progesterone tendons, they also work and helps regulate body and relaxin increase the to maintain an upright temperature as well as looseness of the joints, posture. The increasing forming a protective ultimately designed to weight of the fetus barrier. Skin, hair, and allow a baby’s relatively causes the mother's nails tend to look large head to pass posture to change healthier during through the pelvis during pregnancy, pregnancy; less hair is during delivery. placing extra strain on lost, so it looks thicker Intestinal absorption the muscles, ligaments, and more lustrous; and of calcium (to make and joints in the lower nails are smooth the fetal skeleton) back. Also, many and not brittle. doubles during pregnant women Pigmentation pregnancy. After notice a separation changes, such as birth, extra calcium of the abdominal the appearance of for breast milk is muscles, which dark patches on temporarily “taken” allows the belly to the face (chloasma), from the mother’s grow too. The separated and a dark vertical line skeleton to meet the muscles usually rejoin in (linea nigra) down the demands of a newborn. the weeks after childbirth. abdomen, may also develop.

27 Hypothalamus The brain’s master gland controls THE MALE hormone production Pituitary gland REPRODUCTIVE SYSTEM This tiny structure secretes hormones to stimulate the The key parts of the male reproductive system, the penis and testes, testes directly work together with glands and other structures to produce and deliver sperm, which may combine with an egg to create a new life. The system begins to develop just six weeks after fertilization. THE REPRODUCTIVE ORGANS The male reproductive system is made up of the penis, a pair of testes that sit within the scrotum, a number of glands, and a system of tubes that

THE MALE REPRODUCTIVE SYSTEM I THE MALE REPRODUCTIVE Penis connects them all. Once sperm have developed within each testis, they travel When erect, the penis can deliver to each epididymis to mature and for temporary storage. They continue their semen during journey along each vas deferens and then through the ejaculatory ducts to ejaculation join the urethra, which runs the length of the penis. Columns of spongy tissue

ANATOMY ANATOMY within the penis contain a rich network LOCATING ORGANS OF THE MALE of blood vessels that ﬁll with blood in Testis REPRODUCTIVE SYSTEM Structures within The penis and testes are located outside response to sexual arousal (see pp.64–65). each testis the body cavity. The processes that occur This engorgement causes the penis to produce and in the testes are under hormonal control prepare the sperm from the pituitary gland, which is become erect and able to deliver sperm ready for delivery regulated by the hypothalamus. to the top of the vagina (see pp.66–67).

SPERM FACTORIES Sperm Seminal fluid 2–5% 65–70% Sperm are produced in abundance within the seminiferous tubules of the testes, a process called Prostate fluid spermatogenesis (see pp.32–33). The developing 25–30% sperm are protected and nourished by Sertoli cells, which extend inward from the walls of the tubules. Once a sperm leaves the testes, it moves on to the epididymis, where it matures and can be stored for up to four weeks. Semen is made up of sperm cells suspended in secretions—about THE CONSTITUENTS OF SEMEN SPERM UP CLOSE 100 million sperm per 0.03 fl oz (1 ml) of fluid. Only a small percentage of semen is sperm; The basic structure of sperm can clearly be seen most is made up of milky white fluids, on this microscopic view of multiple sperm. Each About 0.1–0.17 fl oz (3–5 ml) of semen is delivered mainly produced by the prostate gland sperm consists of a head, which carries half of a via the urethra of an erect penis at male orgasm. and the seminal vesicles. man’s genetic information, and a long, thin tail.

TESTOSTERONE 1,100 The principal male hormone testosterone triggers development of the reproductive 1,000 organs and the changes that occur at puberty, including deepening of the voice 900 and a growth spurt (see p.31). Testosterone must be present for sperm production 800 to take place. As with hormone production 700 and egg development in women, testosterone 600 and sperm production in men are controlled 500 by hormones secreted by the pituitary gland 400 (FSH and LH), which in turn are regulated by 300 the brain’s hypothalamus. Testosterone is 200

produced by the Leydig cells located between FOR MALES (ng/dL) TESTOSTERONE TOTAL the seminiferous tubules in the testes. 100 0 0.6 –9 10 –13 14 –15 16 –19 20 – 39 40 –59 60 AND TESTOSTERONE CRYSTALS OVER Outside the body, testosterone can be AGE (YEARS) crystallized and viewed under a microscope. A LIFETIME OF TESTOSTERONE PRODUCTION Testosterone in the fetus causes the testes Boys and men produce signiﬁcant levels of testosterone to descend into the scrotum before a baby throughout their lives, from puberty until well after the boy is born. From birth until the surge at age of 60. Peak testosterone levels are present in young puberty, testosterone levels are very low. men between the ages of 20 and 40. 28 THE MALE REPRODUCTIVE SYSTEM Ureter THE MALE REPRODUCTIVE ORGANS Seminal vesicle Carries urine from IN CROSS SECTION Secretes ﬂuid into the kidney to the The male reproductive system comprises the ejaculatory duct bladder (part of the a number of organs and tubes that are to transport sperm urinary system) responsible for the production, storage, and delivery of sperm. The male genitalia consist of Sacrum Rectum the penis (with its central tube, the urethra) and the scrotum, containing the two testes.

Prostate gland Secretes part of the ﬂuid that makes up semen Bladder

I ANATOMY

Vas deferens Carries semen from the epididymis to the ejaculatory duct

Pubic symphysis

Corpus cavernosum Together with the corpus spongiosum, makes the penis erect

Urethra Carries semen and urine out through the penis

Corpus spongiosum Becomes engorged with blood to make the penis erect

Anus

Ejaculatory duct Epididymis Carries sperm from A long, coiled tube sitting each vas deferens on top of the testis, in to the urethra which sperm mature

Pampiniform plexus Scrotal skin Network of veins feeding into testicular vein Dartos muscle Relaxes in hot weather to Testicular artery keep testes cool and away from body; contracts when Vas deferens cold to prevent sperm from getting too cold Foreskin Fascia (prepuce) Covers and Layer of connective LAYERS OF THE Glans penis The bulbous end protects the tissue around SCROTUM of the penis head of the the testis The testes are surrounded penis by the layers of the scrotal Epididymis wall: the outer skin, the Testis muscular layer, the layers Scrotum Testis of connective tissue The sac that One of a pair of Tunica vaginalis (fascia), and the innermost contains the structures that layer, the tunica vaginalis. testes produce sperm The testes are linked to and testosterone the circulation by a system of arteries and veins. 29 THE PROSTATE GLAND, PENIS, AND TESTES Sperm are developed and delivered by the prostate gland, penis, and testes. The prostate gland, located in the lower pelvis, and the penis and testes, which are outside the body cavity entirely, are connected by a system of incredibly long tubes. THE PROSTATE GLAND THE PENIS 1 About 1 /2 in (4 cm) across, the prostate gland surrounds the The penis consists of a long shaft with a widened end, the glans. urethra (the tube that carries urine from the bladder) as It has two functions: to deliver sperm and to expel urine. A penis it emerges from the bladder. It produces a thick, milky, contains three columns of erectile tissue: two corpus cavernosa, alkaline fluid that forms about 20 percent of semen volume which lie alongside each other; and one corpus spongiosum, which and counteracts the acidity of other fluids encircles the urethra. When arousal occurs, blood vessels in Veins in semen. The prostate gland is under the these columns become engorged, making the penis erect 1 2 THE PROSTATE GLAND, PENIS, AND TESTES GLAND, I THE PROSTATE control of testosterone as well as nerves (see pp.64–65). The average penis is about 3 / in 1 that, when arousal occurs, stimulate (9 cm) long but can “reach” up to 7 /2 in (19 cm) Ureter release of fluids by the prostate, when erect. Ejaculation is a reflex action.

seminal vesicles, and vasa Arteries deferentia. These ﬂuids, together ANATOMY ANATOMY Corpus cavernosum with the sperm, are released from the penis at ejaculation. Urethra

Corpus spongiosum THE PENIS IN SECTION

MALE REPRODUCTIVE ORGANS The organs and tubes of the male Bladder reproductive system are closely allied with those of the urinary system, with the penis featuring Seminal vesicle in both. Valves at the base of the Secretes yellowish bladder remain closed at ejaculation so that urine and semen cannot mix. ﬂuid to suspend Bulb of sperm in semen penis

Prostate gland

THE PROSTATE IN SECTION Cowper’s gland This microscopic view of prostate tissue Releases alkaline Corpus shows multiple secretory cells that release ﬂuid into the cavernosum alkaline ﬂuid, which neutralizes the acidity of urethra during semen, thereby improving sperm motility. sexual arousal

Vas deferens THE TESTES Measures about 1 The paired testes are the powerhouses of the male reproductive 17 /2 in (45 cm); there Corpus are two, one from spongiosum system, producing sperm and the potent hormone testosterone. The each testis, (together 1 testes are 1 /2–2 in (4–5 cm) long and comprise multiple conical sections they are the vasa Testis deferentia) (lobules), each containing tightly coiled tubes (seminiferous tubules) where sperm develop (see pp.32–33). The testes hang together in the scrotal sac. Within the scrotum, Seminiferous tubule the temperature is 2–3.5° F (1–2° C) About 39 ft (12 m) of coiled tubules where lower than body temperature—the sperm develop on a optimal environment for sperm continuous basis production. Leydig cells, clustered between the seminiferous tubules, Epididymis secrete testosterone. About 20 ft (6 m) of tubes are packed into this area SEMINIFEROUS TUBULES IN SECTION This magnified image shows seminiferous tubules packed with immature sperm Lobule of testis Glans and Sertoli cells; Leydig cells (stained Partial walls separate the testis penis green–brown) sit between the tubules. into about 250 compartments 30 MALE PUBERTY MALE PUBERTY The onset of puberty, brought about by the hormone testosterone, is a time of great physical and emotional changes. The body alters in shape and appearance, Height and within the body the sexual organs mature in readiness for sperm production. I ANATOMY Men are taller than women due to the PHYSICAL CHANGES delayed onset of puberty. Puberty in boys (spermarche) tends to start between the ages of 12 and 15, on average two years later than it occurs in girls. The physical changes are very Facial hair The need to shave begins marked; some relate to the sexual organs themselves, the most obvious being during puberty as hair starts to the enlargement of the genitals; others appear unrelated, but all are the result grow above the lips and on the cheeks and chin. of the dramatic increases in testosterone levels within the body. Puberty is accompanied by a final spurt of growth. Its later onset in boys than girls gives boys significantly more time to Broadened chest Muscular body and body hair Testosterone grow before they reach their final adult height. The ribcage promotes muscle expands and growth all over shoulders broaden; the body. body hair appears WHY DOES A BOY’S VOICE BREAK? coarser.

Testosterone affects both the cartilage parts of the larynx (voice box) and the vocal cords themselves. The vocal Pubic hair cords grow 60 percent longer and thicker, and therefore Hair starts to start to vibrate at a lower frequency (making the voice grow at the base of the penis; it Enlarged genitals sound deeper). At the same time, the larynx tilts and can becomes thicker The penis and testes start to stick out, forming the Adam’s apple. and coarser grow larger; it is over time. normal for one testis to hang lower than Thyroid the other. cartilage

Vocal Cut edge of cartilage cords Ligament Bone growth Under the PHYSICAL DEVELOPMENT Cricoid CARTILAGE CHANGES inﬂuence of AT PUBERTY cartilage The cartilage in a boy’s testosterone, bone A range of physical changes maturation ends larynx is highly sensitive occur as a result of the surge and growth to testosterone levels. in testosterone that heralds During puberty, this gradually stops. Trachea puberty. Alongside genital cartilage (shown in blue) growth is the development grows larger and thicker of secondary sexual ADULT LARYNX to reach its adult size. characteristics, such as the BEFORE PUBERTY AFTER PUBERTY growth of facial and pubic hair.

KEY A SELF-REGULATING SYSTEM HORMONAL CHANGES INSTRUCTIONS FROM THE BRAIN Hypothalamus From puberty, the brain prompts the From the age of about 10 years, the hypothalamus development of the testes, which INHIBITION VIA in boys begins to secrete a hormone (GnRH) that NEGATIVE FEEDBACK make testosterone. Moderate levels GnRH of testosterone suppress the brain’s causes the pituitary gland to release hormones— inﬂuence via inhibiting the secretions FSH and LH—that control the testes. FSH, and to a of GnRH, LH, and FSH. lesser extent LH, promotes sperm production, but Anterior pituitary gland LH also stimulates the secretion of testosterone. High levels of testosterone cause the growth spurt and other pubertal changes. Once stabilized after suppresses suppresses FSH and LH LH FSH FSH and LH puberty, testosterone secretion secretion levels in the body are regulated by a system Testis of negative feedback. suppresses GnRH Testosterone Inhibin secretion The Leydig cells secrete The testes’ Sertoli cells, TEENAGE BOYS AND testosterone, which which nurture and support AGGRESSION boosts growth throughout developing sperm cells, also It has been suggested that the the body and controls secrete a hormone to help surges of testosterone that occur the development of regulate production of sex in the teenage years in boys can sexual characteristics. hormones in males. be associated with increased levels of aggression. 31 Scrotum Vas deferens Pampiniform plexus Rete testis Nucleus of Network of veins that Network of Tight junction Sertoli cell takes blood away from ducts that feed Opens and the testis and penis sperm into the closes, like a epididymis zipper, to allow movement of the developing Epididymis sperm toward the lumen

Cytoplasmic bridge Constant connection HOW SPERM IS MADE I HOW between cells developing at the same time

LOCATION OF TESTES ANATOMY ANATOMY Basement Lobule of testis membrane Cone-shaped Outer edge of area containing the tubule seminiferous tubules; about 250 in Spermatogonium each testis Immature cell that either develops into a Septum spermatocyte or copies Fibrous division that TESTIS IN itself to provide a constant separates lobules SECTION supply of immature cells for future development SPERMATOGENESIS UP CLOSE Within the seminiferous tubules of a testis, a sperm begins its life as SPERMATOGONIA an immature spermatogonium. As 1 These immature cells it travels inward from the outer lie close to the tubule’s basement membrane toward the basement membrane. These lumen, it undergoes several divisions are the ﬁrst cells in the to become a mature sperm. process of spermatogenesis.

Sertoli cell Tall, column-shaped cell that ﬁlls the gaps between PRIMARY SPERMATOCYTES developing spermatogonia, 2 The resulting cells of the protecting, supporting, and spermatogonia division, known as nourishing them. primary spermatocytes, move away from the basement membrane on their developmental journey HOW SPERM IS MADE toward the lumen of the tubule—their ultimate destination. The development of mature sperm (spermatogenesis) is a continuous process from puberty. About 125 million sperm can be produced every day and can then be stored for up to four weeks.

Within the seminiferous tubules of the testes, sperm (spermatozoa) are continually developing from immature cells (spermatogonia) into ever-more-mature forms until they have the potential to fertilize an egg and form new life. The optimum temperature for sperm production is lower than body temperature, so the testes hang outside the body cavity in the scrotum. Spermatogenesis is a gradual process, taking about 74 days from start to ﬁnish. Development begins at the outer border of the tubule and continues as the cells divide and move toward the center of Seminiferous tubule About 39 ft (12 m) the tubule, the lumen. of these tubules are packed into the lobules MILLIONS OF SPERM of each testis This electron micrograph shows a seminiferous tubule within a testis—the site of spermatogenesis—packed with sperm. 32 Spermatogonium HOW SPERM IS MADE ANATOMY OF THE SPERM Primary spermatocyte Sperm are perhaps the tiniest cells in the body, yet they can propel themselves along and contain half the genetic information needed Secondary spermatocyte for a new individual to develop. The head contains the nucleus and at the front the acrosome, which contains enzymes that help it SECONDARY SPERMATOCYTES penetrate an egg. The midpiece contains the mitochondria, which 3 Primary spermatocytes undergo a specialized type of cell division (meiosis, see provide all the energy a sperm needs on its long journey. Finally,

p.51) that halves their number of chromosomes. the tail contains threads of tissue that slide next to each other I ANATOMY The resulting secondary spermatocytes have enabling the whiplike action that propels the sperm forward. only 23 chromosomes. Meiosis is necessary to produce a sperm that can fertilize an egg to achieve the right number of chromosomes. Head Nucleus Acrosome Contains the sperm’s highly Caplike coating condensed DNA contains enzymes to Early spermatids Midpiece as 23 chromosomes help penetrate an egg

Late spermatids PARTS OF A SPERM Neck SPERMATIDS 4 Secondary spermatocytes quickly develop into spermatids, which start to form an acrosome, condense their DNA, and develop a deﬁned neck, midpiece, and tail. They are now almost fully developed sperm, which are then transported to the epididymis where they Tail mature and become motile.

Sperm Axoneme Helps generate the whiplike Centriole action of the Collection of tiny sperm’s tail Spiral mitochondria tubes that help in Energy-producing the arrangement structures (needed to of chromosomes power swimming) at cell division packed into a space-efﬁcient spiral

SEMEN ANALYSIS

This test forms a crucial part of ABNORMAL SPERM assessing couples with fertility Sperm can be abnormal in a variety problems. Several factors are of ways, such as having two heads, routinely measured. two tails, or a very short tail. Abnormally shaped sperm may not FEATURES OF NORMAL RANGE be able to move normally or to THE SEMEN OF VALUES fertilize an egg. Some abnormal sperm are found in most normal Sperm count More than 40 million semen samples. However, if the per ejaculate numbers are too high, fertility is likely to be affected. Semen volume More than 0.07 ﬂ oz (2 ml)

TWO HEADS

Sperm More than 70 percent morphology with normal shape (shape) and structure TWO TAILS Sperm motility More than 60 percent with normal forward movement TAIL TOO SHORT

pH of semen 7.2–8.0

HEAD TOO BIG Lumen of seminiferous White blood cells None (their presence tubule may indicate infection) NECK TOO LONG Sertoli cell 33 THE FEMALE Hypothalamus The brain’s “master gland” triggers and controls hormone REPRODUCTIVE SYSTEM secretion. The interconnected organs and tubes of the female

Pituitary gland reproductive system can provide everything needed to This tiny structure secretes hormones conceive and nurture a fetus. Once a baby is born, the system to stimulate the ovaries. also provides it with the ultimate nourishment—breast milk. Breast REPRODUCTIVE ORGANS Made up of lobules, breasts produce milk The uterus, vagina, ovaries, and fallopian tubes coordinate their actions to in response to hormonal changes. generate new life. The vagina receives an erect penis as it delivers sperm to the entrance of the uterus, the cervix. Eggs are stored and develop within the ovaries. Each month one egg (or, very rarely, two eggs) is released and moves along one Ovary Eggs develop here fallopian tube to its ultimate destination, the uterus. If the egg has combined with and are released a sperm en route, it will develop into an embryo (later called a fetus) and grow every month. within the uterus, which stretches to many times its original size over the next Fallopian tube nine months. The ovaries also produce hormones key to the reproductive process. This transport tube propels mature eggs from the ovary to the uterus. REPRODUCTIVE LIFE At birth, the ovaries of a baby girl Uterus Every month its contain one to two million immature lining prepares for eggs, but the number dwindles over time; an embryo but is shed if fertilization by puberty only about 400,000 remain. does not occur. Usually, only one egg is released every month. The time available to women Vagina to have a baby is ﬁnite, although new This elastic tube can stretch to allow a technologies can prolong the window baby to be born. of reproductive opportunity for some women. Generally, the reproductive years, IN THE FAMILY WAY LOCATING ORGANS OF THE which start at puberty, end around the Mature eggs are released from the ovaries FEMALE REPRODUCTIVE SYSTEM age of 50 when menopause occurs; from puberty until menopause. A woman’s The main reproductive organs lie within the pelvis. fertility begins to decline gradually from Their actions and those of the breasts are under men, meanwhile, can continue to father about the age of 27, but starts to drop the control of certain areas of the brain. children to a much greater age. more rapidly from the age of 35.

SEX HORMONES EFFECTS OF SEX HORMONES ON THE FEMALE BODY Produced primarily by the ovaries, The female sex hormones estrogen and progesterone have key roles the female sex hormones estrogen and in the menstrual cycle, as well as more general physical effects. The progesterone are responsible for the sexual male sex hormone testosterone is also present in women. development and physical changes that occur at puberty (see p.43), the monthly HORMONE EFFECTS menstrual cycle (see pp.44–45), and fertility. Estrogen Estrogen promotes the growth of the sex organs and the development of the physical changes that occur Their production is under the control of two at puberty—secondary sexual characteristics. In the hormones—luteinizing hormone (LH) and ovaries, it enhances the development of eggs, and it follicle-stimulating hormone (FSH)—that thins the mucus produced by the cervix so that it is easier for sperm to penetrate. Estrogen levels peak just are produced by the pituitary, the tiny gland before egg release (ovulation). It also stimulates growth at the base of the brain, which is in turn of the uterine lining (endometrium). regulated by the hypothalamus. The sex Progesterone Progesterone helps prepare the endometrium hormones also influence emotions: many every month and maintains it if pregnancy occurs. If pregnancy doesn’t occur, progesterone levels fall women experience mood changes during and menstruation results. Progesterone also prepares PROGESTERONE CRYSTALS their menstrual cycle, which correspond with the breasts for milk production (lactation). This highly magnified and color- enhanced micrograph shows crystals hormonal fluctuations. In addition, the male Testosterone Despite circulating in relatively low levels, testosterone of progesterone. This hormone helps sex hormone testosterone also exerts effects does affect the female body. It is responsible for the prepare the uterine lining for pregnancy within the female body, although it is present growth spurt of puberty and the closure of growth by causing it to thicken and its blood plates that signals the end of childhood growth. supply to be increased. at relatively low levels. 34 THE FEMALE REPRODUCTIVE SYSTEM Ovarian ligament The ovaries are Fallopian tube connected to the uterus In most months one mature Sacrum by this band of tissue. egg passes along a fallopian tube; this is where fertilization occurs.

Fimbria This is one of many ﬁngerlike projections at the fallopian tube’s outer end.

Ovary Eggs mature and hormones are produced within this structure.

Uterus

This highly muscular organ accommodates and I ANATOMY nurtures a developing fetus.

Fundus of uterus This is the top of the uterus. During pregnancy, its position gives an indication of fetal size. Peritoneum The abdominal cavity is lined by this smooth membrane.

Myometrium The muscular layer of the uterine wall contracts during labor. Endometrium The lining of the uterine wall thickens every month in preparation for pregnancy.

Round ligament of uterus This ﬁbrous band of tissue helps keep the uterus in position.

Pubic symphysis This slightly ﬂexible joint connects the pubic bones at the front of a woman’s pelvis.

Pubis

Labia majora Rectum Cervix Vagina Bladder Urethra The outer folds of skin The uterus narrows This elastic tube that protect the delicate at its lower end, from the uterus genital tissue. the cervix. receives the erect Clitoris penis during sexual This area of erectile intercourse and is tissue is highly Urethra the birth canal. sensitive to sexual FEMALE REPRODUCTIVE stimulation. Vaginal opening ORGANS IN CROSS SECTION The organs all sit within the lower pelvis, close Labia minora to the bladder and lower digestive tract. There These inner ﬂaps of is room above the uterus to allow expansion skin offer another FEMALE EXTERNAL if pregnancy occurs. The clitoris and the layer of protection. GENITALIA The labia majora and entrances to the urethra and vagina are Perineum relatively close; all are protected by the labia. minora protect the This area runs from delicate tissues of the the vaginal opening clitoris and the opening to to the anus. the vagina and the urethra. The external female Anus reproductive structures are together called the vulva. 35 THE OVARIES AND FALLOPIAN TUBES An egg starts its life in an ovary, where it is stored and then matures until ready for release at ovulation. The mature egg travels along a fallopian tube to the uterus where, if it has been fertilized en route, it embeds in the wall and pregnancy begins. THE OVARIES Lying on either side of the pelvis, the paired ovaries provide mature eggs (ova) that, if combined with a sperm, can form a new human being. They also produce estrogen and progesterone; these hormones control sexual development (see p.43) and the menstrual cycle Ampulla (see pp.44–45). The ovaries are only the size of almonds, yet they This long section is contain tens of thousands of immature eggs. From puberty, eggs the most common site of fertilization. and their containing follicles begin a cycle of development and release from the ovary. When an egg is released, it enters X-RAY VIEW a fallopian tube. The empty follicle Ovarian In this image, the uterus, ovaries, remains in the ovary and medulla and fallopian tubes are highlighted The central by a contrast dye delivered by the produces hormones to part of the probe seen in the vagina. sustain a pregnancy. ovary contains blood vessels and nerves.

Primordial follicle This is the earliest immature follicle, present at birth.

Primary follicle Ovarian ligament As a follicle’s development This band of tissue gets underway, it is ﬁrst connects the ovary called a primary follicle. Uterus to the uterus. This muscular organ Secondary follicle accommodates the After further development, developing embryo, a primary follicle becomes later called the fetus. a secondary follicle.

Blood vessels

80 0 YEARS Fat cells, or Ovarian cortex 12 adipose tissue, Follicles in various produce a small Ovaries secrete stages of development 16 amount of estrone after are found here. menopause estrogen Corpus luteum Preovulatory THE ESTROGEN FAMILY Formed from the follicle Ovarian KEY The estrogens are a group of similar chemicals, empty follicle, this This term is used ESTRADIOL follicles produces both for the mature ESTRIOL produce three of which are produced in significant amounts: estrogen and follicle just ESTRONE estradiol from estradiol, estriol, and estrone. The levels of these progesterone. before ovulation. puberty to hormones differ at various stages of a woman’s life, but menopause the main one—estradiol—predominates throughout her INSIDE AN OVARY AND FALLOPIAN TUBE 50 Placenta makes reproductive life, from menarche to menopause. Estrogen estriol during is mainly produced in the ovaries, but smaller amounts Mature eggs are released from the surface 40 pregnancy are manufactured in the adrenal glands, which lie on top of the ovary into the pelvis and are drawn into the nearby funnel-shaped end of A LIFETIME OF ESTROGENS of the kidneys, and in fat cells (adipose tissue). Being the tube by the movement of fingerlike Types of estrogen vary at different significantly overweight can be associated with higher projections called fimbriae. The egg is stages of a woman’s life. Estradiol levels of estrogen, which may affect the functioning of propelled along the length of the tube 1 dominates the reproductive years. the ovaries and reduce fertility. (about 4 /2 in/12 cm) to the uterus. Fallopian tube Epithelium The convoluted interior THE FALLOPIAN TUBES Highly folded surface is made up of Located on either side of the uterus, the surface, packed folds, and a layer of with ciliated cells smooth muscle fallopian tubes transport mature eggs from and peg cells encircles the tube. the ovaries to the uterus. Various features

of the tubes facilitate an otherwise immobile Lumen egg to get to its destination—the ﬁmbriae Convoluted cavity within capture the egg initially, and the muscular fallopian tube wall and the beating cilia on the tube’s interior

propel the egg along. A fallopian tube has Muscular wall three main parts: the outermost infundibulum, Layer of smooth muscle that the ampulla (the usual site of fertilization), encircles tube and the innermost isthmus. Each region varies in diameter and microstructure; for example, Serosa the muscle in the isthmus wall is particularly Outer layer of tube wall thick to enable it to deliver the egg into the uterus. If fertilization occurs, the fertilized egg MICROSTRUCTURE OF A FALLOPIAN TUBE This microscopic view shows a cross section (zygote) divides as it passes along the tube through the ampulla region of a fallopian tube; ready for implantation in the uterus wall. the wall’s different layers are clearly visible.

REGIONS OF A FALLOPIAN TUBE Isthmus Ampulla The widest region is the funnel- The shortest The longest shaped infundibulum, which allows and narrowest section, which the egg to be swept in. The ampulla region, which has a clear bulge and the innermost isthmus have opens into highly muscular walls for effective the uterus propulsion of the egg or embryo.

Infundibulum Labyrinthine The outermost epithelial Fimbria section, closest surface This delicate, to the ovary captures ﬁngerlike ovum projection helps draw the egg into the fallopian tube.

Simple Thin layer lumen to of muscle promote transport

Expanded Muscular lumen allows wall propels room for embryo into CROSS SECTION CROSS SECTION fertilization CROSS SECTION the uterus OF ISTHMUS OF AMPULLA and transport OF INFUNDIBULUM

HOW A FALLOPIAN TUBE PROPELS AN EGG

From the moment the egg MAGNIFIED (ovum) leaves the ovary, the Muscle contracts Muscle relaxation EPITHELIAL CELLS fallopian tube is working to Fallopian A section of smooth The muscles in the region Some lining cells deliver it first to the middle tube muscle in the wall of the ahead of the contraction are covered with fallopian tube contracts to relax to allow the egg tiny hairs that beat third of the tube in push the egg forward. to move forward. to aid movement preparation for penetration of the egg along the by a sperm (fertilization), tube; others provide and then on to the uterus. nutrition for the egg. The movement of the fimbriae at the outer end of the tube combined with the beating of the cilia create a Egg Ciliated cell current that draws the egg (ovum) Creates into the flared end of the currents to tube. Once inside, waves of waft an egg PERISTALTIC PROPULSION along muscular contraction and The coordinated sequence of Peg cell the action of cilia transport contraction and relaxation propels To the Nurtures and it to the uterus. the egg along the fallopian tube. uterus supports an egg

37 CAPTURING THE EGG Delicate projections called ﬁmbriae form one end of a fallopian tube. Their highly folded surface ensures that, when they shift toward the point on an ovary from which an egg is released, they capture and then guide the egg into the tube.

THE UTERUS, CERVIX, AND VAGINA INSIDE THE FEMALE REPRODUCTIVE TRACT The uterus, the central area Every month, the lining of the uterus undergoes structural changes of the female reproductive tract, is connected to the to prepare for the possible arrival of a fertilized egg. The uterus is two fallopian tubes at its the home for a developing fetus for the duration of a pregnancy; the uppermost corners and to the vagina below, the exit cervix and vagina are its exit points to the outside world. being formed by the cervix. THE UTERUS THE LINING OF THE UTERUS A highly muscular organ, the uterus is the site of The uterine lining, the endometrium, is composed of a functional layer and a basal layer; the former implantation for a fertilized egg. During pregnancy, thickens each month until a fall in hormones it enlarges to many times its size as a fetus grows. prompts it to be shed during menstruation. The I THE UTERUS, AND VAGINA CERVIX, The uterine wall is made up of three layers: the outer basal layer remains to renew the functional layer Uterine once menstruation is over. The endometrium has a perimetrium, the middle muscular myometrium, and cavity unique blood supply: straight arteries in the basal the inner endometrium. The endometrium builds up layer and spiral arteries in the functional layer. Most Endometrium every month in preparation for a fertilized egg and arteries in the body branch into arterioles and

ANATOMY ANATOMY Innermost layer then is shed if fertilization fails to occur. The uterus capillaries before rejoining to form venules and of the uterus can be divided into sections: the upper dome-shaped veins. Spiral arteries do this but they also have a shunt connecting them directly to veins. When fundus, the main body, and the neck, or cervix. Myometrium hormone levels fall, the resultant shrinkage in the Middle endometrium forces spiral arteries to coil until they muscular layer of the uterus Retroverted restrict the blood ﬂow, which diverts via the shunts uterus until stopping. Tissue death sets in as cells of the Perimetrium functional layer do not have access to blood, and Outermost Anteverted the capillary plexi and venous “lakes” rupture, all layer of the uterus of which leads to the bleeding of menstruation. uterus

Bladder Functional layer Highly regenerative layer with specialized Basal layer blood vessels Rectum Ever-present layer that helps rebuild THE POSITION OF THE UTERUS the functional The angle of the uterus can vary, but in most women, layer each cycle it is tilted forward (anteverted); about 20 percent of women have a uterus that tilts backward (retroverted).

THE EXPANDABLE UTERUS

The wall of the uterus consists mainly of muscle, giving it an amazing capacity to enlarge to accommodate the growing fetus. The fundal height (see below) is monitored as a measure of fetal growth. Conveniently, the fundal height in centimeters Capillary usually corresponds to the length of the pregnancy in weeks. plexus Network of PREGNANT single-cell- walled UTERUS SIZES Straight vessels that The distance artery connect from the pubis Supplies only arterioles to the top of the the basal layer to venules uterus is called the Shunt fundal height. It is Spiral artery Connection measured regularly Grows faster than between spiral throughout the surrounding artery and venous tissue, so coils pregnancy. “lake”; used as tighter as endometrium Endometrial gland Venous “lake” functional layer starts to shrink Secretes mucus and Blood pools here The fundal height other substances during before rupturing nears completion is greatest at 14 in the menstrual cycle at the start of (36 cm) at about menstruation 36 weeks THE STRUCTURE OF THE ENDOTHELIUM At 12 weeks the The thin layer of cells that lines the endometrium is fundal height is called the endothelium; its detailed structure helps 1 4 /2 in (12 cm) explain its ability to shed and renew itself every month. It has unique systems of blood vessels: straight arteries Pubis in the basal layer; and spiral arteries within the functional layer, which coil as the layer grows. 40 THE UTERUS, CERVIX, AND VAGINATHE UTERUS, Fundus of uterus Top part of the uterus THE CERVIX The neck of the uterus, more commonly referred to as the cervix, opens into the vagina at the external os, thereby forming a connection between the uterus and the vagina. The highly specialized epithelial cells that line the convoluted surface of the cervical canal present an obstacle course for sperm to navigate. They also secrete mucus, the nature and content of which varies during the menstrual cycle. The changes make mucus hostile to sperm for most of the I ANATOMY Fallopian tube cycle and then sperm-friendly around Specialized transport ovulation (see pp.44–45). If sperm- tube that carries eggs from the ovary after friendly mucus is present, it acts as a ovulation to the uterus CERVIX VIEWED FROM BELOW reservoir, prolonging the life of sperm This view of the cervix shows the external os. In past the usual 24 hours. A mucus plug a woman who has never had a vaginal delivery, this Internal os os is tightly closed; in a woman who has given birth Inner boundary of seals the cervix during pregnancy, vaginally it appears less tightly closed. Here the the cervical canal, mucus appears whitish and watery. where it meets protecting it from the outside world. the uterus FEATURES OF CERVICAL MUCUS Cervical canal SECRETORY EPITHELIUM OF THE CERVIX Has a vertical ridge The epithelium of the cervix contains columnar The amount of cervical mucus varies as it is front and back from cells, which are responsible for secreting the which numerous cervical mucus. The production is affected by affected by the hormones of the menstrual folds (rugae) branch the hormonal changes of the menstrual cycle. cycle. Mucus can be used as an indicator of the most fertile times in a cycle (see p.79). Convoluted surface Folded surface of cervical SPERM–FRIENDLY HOSTILE canal presents an obstacle MUCUS MUCUS course to sperm after sexual intercourse Is produced in Is produced in abundance small amounts Columnar epithelium Cells here secrete various Is more stretchy Is less stretchy chemicals as well as mucus and elastic and elastic

Vaginal fornix Contains more water Contains less water Deepest portion of and so is thinner and so is thicker the vagina, extending into recesses created by the cervix Is more alkaline Is more acid (has a higher pH) (has a lower pH)

Has a strandlike Has a globular structure structure

Cervical lumen Has no anti-sperm Contains anti-sperm Space in the antibodies antibodies middle of the canal

THE VAGINA Ruga This elastic, muscular tube connects the uterus with the vulva. It receives the penis during sexual intercourse and expands External os greatly to provide the birth canal for the delivery of a baby. Outer boundary of the cervix, where it The vagina also allows menstrual blood and tissue to leave meets the vagina the body during menstruation. The vaginal wall is made up of an outer covering, a middle layer of muscle, and an inner layer of epithelium that is formed into ridges (rugae). The surface does not produce secretions itself but rather is lubricated by secretions from the cervix. Vagina Elastic, muscular tube VAGINAL RUGAE The vagina contains natural that connects the The ridges of the vaginal lining, known bacteria, which creates a very cervix to the vulva; as the rugae, allow the highly elastic ridges called rugae walls of the vagina to expand during acidic environment; this helps line the vagina sexual intercourse and childbirth. to protect against germs. 41 THE BREASTS Breast function is closely allied to the functions of the reproductive organs. Breast development occurs at puberty; further adaptations are made during and after pregnancy to produce breast milk for a newborn. BREAST TISSUE The breasts consist of glandular tissue, fat, and some supporting tissue that helps give the breasts their shape. The breast tissue is arranged in lobules, within which gland cells are formed into clusters called alveoli. Tiny tubes from the alveoli come together to form the main ducts that open onto the nipple. During pregnancy, high levels of estrogen and progesterone cause the glands and ducts to prepare for lactation (see pp.174–75). The shape of a woman’s breasts is determined by her genes, the amount of fatty tissue the breasts contain, and muscle tone.

Fatty tissue

Lung

Blood vessel

Pectoral muscle

Lobule

Nipple Areola The center has tiny holes Circular through which milk can ﬂow pigmented area around a nipple Milk duct

Nipple Lies at the center A BREAST IN CROSS SECTION of the areola Breast tissue is arranged in a daisy pattern of 15–20 lobules. Ducts from these lobules drain milk directly to the nipple. The breasts Milk duct are attached to the muscles beneath them Tube that transports Rib milk from the lobule by strong ﬁbrous tissue. to the nipple

Ductule Feeds into a milk duct

Lobule Structure containing milk-producing cells

Alveolus One of many glandular structures at the end of each lobule

Epithelial cell Produces and releases milk during lactation FEATURES OF A BREAST Adipose cell The breast is a highly glandular structure. The One of multiple fat size and shape varies, but all contain a similar cells that make up amount of milk-producing tissue. The nipple, the fatty tissue which is surrounded by the areola, contains MICROSTRUCTURE OF THE BREAST muscle that can cause it to become erect when This enlarged view of the breast tissue stimulated. The nipple receives milk via the milk shows the alveoli, which contain the ducts that drain the lobules. milk-producing cells, embedded in fatty tissue. They are drained by tiny ductules. FEMALE PUBERTY

FEMALE PUBERTY BREAST DEVELOPMENT This important stage in life, when sexual organs develop and The breast changes of puberty occur in five marked physical changes occur, tends to begin at the age of defined stages. Firstly, during thelarche, the nipple appears higher. Following this, the 10–14 years in girls and usually lasts for three or four years. breast bud develops behind the areola, causing the nipple and tissue around it to I ANATOMY project from the chest wall. Next, the areola PHYSICAL CHANGES enlarges, accompanied by further breast OF PUBERTY Armpit hair tissue growth. Then, changes in the nipple The changes of puberty take place starts to grow and areola cause them to protrude forward from the rest of the breast. In the final phase in a particular order. Early breast of development, the smooth contour of the development, known as thelarche, is breast is established. Breasts and the first physical change of puberty nipples enlarge Stage III to occur, with the appearance of the Areola becomes Stage IV wider and darker so-called breast bud, when the nipple Areola and and a small area around it start to Pelvis and hips nipple form widen a distinct protrude from the chest wall (see panel, mound right) This is followed within about six months by the growth of hair in the Pubic hair Stage V appears Fully pubic area and, soon after that, armpit formed (axillary) hair. Gradually, the breasts Bones and breast muscles grow swell, more pubic and axillary hair rapidly grows, and the genitals develop. The SECONDARY SEXUAL uterus also enlarges leading up to the first CHARACTERISTICS Stage II menstrual period (menarche). While these The physical changes Breast bud develops changes are taking place, a girl grows that occur at puberty include a marked taller and her body outline changes, with Stage I increase in height and Elevation of the hips and pelvis widening. The onset a widening of the hips, the nipple giving many women of puberty is about two years later in a characteristic PHASES OF DEVELOPMENT boys than in girls. BEFORE PUBERTY pear-shape. AFTER PUBERTY

HORMONAL CONTROL Hypothalamus The onset of puberty is triggered by the release of gonadotropin-releasing hormone (GnRH) by the GnRH brain’s hypothalamus. This hormone stimulates Gonadotropin- the release of two hormones by the pituitary releasing hormone suppresses GnRH suppresses GnRH gland—follicle stimulating hormone (FSH) and secretion secretion luteinizing hormone (LH). FSH and LH cause the Anterior pituitary gland ovaries to produce two hormones, estrogen and progesterone, which are responsible for the major LH FSH changes occuring at puberty and for the monthly Luteinizing Follicle-stimulating menstrual cycles in the years that follow (see hormone hormone suppresses FSH suppresses LH p.44-45). Their release is controlled by a negative- and LH secretion secretion feedback system: as levels of the ovarian

hormones rise, so the levels of the hormones OVARIES

that stimulate their release are reduced. Estrogen Inhibin Follicle cells secrete Granulosa cells in the estrogen as they grow and follicles, along with the develop. Moderate corpus luteum, release estrogen levels inhibit inhibin, which feeds SELF-REGULATION the secretion of GnRH, back to inhibit the OVULATION The hypothalamus and pituitary LH, and FSH. secretion of LH. UP CLOSE gland release stimulatory hormones The tiny pituitary that prompt the ovaries to produce gland at the base of estrogen and progesterone. These Relaxin Progesterone the brain releases the feed back to the brain to regulate The corpus luteum Cells of the corpus hormone LH, which the release of further hormones. makes a small quantity of luteum secrete stimulates the rupture relaxin each month to progesterone. High of a follicle within the KEY relax uterine muscles. levels feed back ovary to release a INSTRUCTIONS FROM (The placenta also to suppress secretion THE BRAIN produces relaxin.) of GnRH and LH. mature egg on a INHIBITION VIA monthly basis. NEGATIVE FEEDBACK 43 THE FEMALE

REPRODUCTIVE CYCLE Ovary Eggs are constantly developing but only one is released every month. To prepare the uterus for the potential implantation of a fertilized egg, a cycle of hormonal fluctuations and changes to the uterine lining occur each month. LOCATION OF THE OVARIES HOW A FOLLICLE MATURES AND RELEASES AN EGG FEMALE REPRODUCTIVE CYCLE FEMALE REPRODUCTIVE Thecal layer Zona pellucida Theca interna Theca externa Fully Development of a mature follicle (folliculogenesis), An organized layer A clear layer Layer within which An outer layer grown which then releases its egg, from an ovary takes formed by stromal cells between blood vessels develop of stromal cells primary primary oocyte and whose cells and fibers oocyte about 28 weeks. Immature eggs remain in the ovaries secrete estrogen Granulosa cells and granulosa in an unchanged state from birth until puberty. But Several layers cells once sexual maturity is reached, the egg-containing of these cells now surround follicles start to mature in clearly defined stages—from primary oocyte a primordial to primary, secondary, and then tertiary ANATOMY I THE ANATOMY Primary follicle. Finally, a mature egg is released (ovulation), oocyte leaving a corpus hemorrhagicum behind, which develops into a corpus luteum. During a woman’s reproductive life, only 400 or so mature eggs will be released; many eggs simply die.

Primary oocyte In a stage of arrested Stromal cell development Embedded within fibers on outer edge of follicle Antrum Fluid-filled Granulosa cell cavity whose Flat cells form a size increases 1 PRIMORDIAL FOLLICLE layer around 23PRIMARY FOLLICLE as follicle SECONDARY FOLLICLE Each month after puberty (and primary oocyte Granulosa cells multiply greatly and develops The thecal layer differentiates further until menopause), gonadotropin and support its become cube-shaped rather than flat. into two layers. Granulosa cells start to secrete hormones (FSH and LH) stimulate growth and Receptors that respond to levels of FSH follicular fluid, which collects in the antrum. the development of several primordial development develop, and there is dramatic growth of Many follicles develop at the same time but follicles within an ovary. both oocyte and follicle. not all mature successfully.

11 12345 6 7 8 910111213 14

WEEKS Days in cycle

HORMONES THE MENSTRUAL CYCLE Every month, a rise in FSH KEY The start of this 28-day cycle sees the shedding of causes egg maturation, and FOLLICLE-STIMULATING HORMONE (FSH) LUTEINIZING HORMONE (LH) the lining of the uterus. This causes blood to exit then LH surges, causing egg release. Estrogen levels peak just ESTROGEN via the vagina, known as menstruation, which lasts prior to egg release and then PROGESTERONE for a few days. After this, the lining of the uterus progesterone levels rise, causing endometrial thickening. begins to thicken again in preparation for the potential implantation of a fertilized egg. The period UTERINE LINING when the uterine lining is most hospitable for Estrogen and progesterone Functional Functional layer cause the endometrium to layer of regenerates to implantation is called the fertile window; it begins 1 endometrium provide the perfect thicken to about /4 in (6 mm) five days before ovulation and is about a week ready for embryo implantation. is shed during environment for menstruation implantation long. If an egg is not fertilized, the uterine lining If fertilization fails to occur, the functional layer is shed and will break down and the cycle begins again. The then rebuilt for the next cycle. fluctuations of four interacting hormones—FSH, LH, estrogen, and progesterone—trigger and control this monthly cycle. The first half of the cycle is called DAYS IN CYCLE 123456789 the follicular phase; the second half, following PHASES OF CYCLE FOLLICULAR ovulation, is known as the luteal phase. 44 THE FEMALE REPRODUCTIVE CYCLE

6 AN EGG Nucleus The egg (ovum) travels along the Contains 23 chromosomes; fallopian tube. If it is not fertilized, when it joins with a sperm, Blood vessel the corpus luteum has a lifespan of will have the two sets of An intricate network two weeks, after which it degenerates Egg 23 chromosomes Corona radiata of capillaries forms into a corpus albicans. As hormone Innermost layer between two thecal levels decline, a new cycle begins. Corona of granulosa cells, layers and circulates radiata firmly attached to blood to and zona pellucida from follicle Zona pellucida Antrum Secondary filled with oocyte follicular fluid Has half the number of chromosomes needed to make new life I ANATOMY

Granulosa cells Mix with theca interna cells and are transformed into the corpus luteum under the inﬂuence of LH

Corpus hemorrhagicum TERTIARY FOLLICLE CORPUS HEMORRHAGICUM Blood clots 4 One developing follicle, known as a tertiary 5 At ovulation, the follicle ruptures to Formed by minor or graaﬁan follicle, becomes dominant and expel the secondary oocyte from the ovary. bleeding in suppresses the growth of the others. Nonidentical The ruptured follicle becomes the corpus ruptured follicle twins result from two codominant follicles, and hemorrhagicum, then the corpus luteum, after ovulation their eggs being fertilized at the same time. which secretes large amounts of progesterone.

15 16 23417 18 19 20 21 22 23 24 25 26 27 28 56

Network of capillaries supplies blood to functional layer

10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

OVULATION LUTEAL

45 THE BLUEPRINT FOR HOW THE HUMAN BODY GROWS, DEVELOPS, AND FUNCTIONS LIES IN THE MASS OF DNA CURLED UP IN THE NUCLEUS OF EVERY CELL. WHEN A NEW LIFE IS CONCEIVED, HALF OF THE GENETIC INSTRUCTIONS CONTAINED IN ITS DNA IS INHERITED FROM EACH PARENT. ALTHOUGH THE BUILDING BLOCKS OF DNA ARE SIMPLE, THE WAY IN WHICH THIS SET OF INSTRUCTIONS IS READ IS A COMPLEX AND REMARKABLE PROCESS. HOWEVER, THINGS CAN GO WRONG. LEARNING HOW THE DNA CODE WORKS, AND BEING ABLE TO DECIPHER IT, CAN HELP US UNDERSTAND HOW CHILDREN INHERIT THEIR PARENTS’ CHARACTERISTICS AND THE CAUSES OF CERTAIN DISEASES. GENETICS THE MOLECULES OF LIFE All living things, including humans, owe their existence to the intricate architecture of a few chemical building blocks that contain the coded instructions needed to build our bodies, keep us alive, and create new life.

KARYOTYPE DNA, GENES, AND CHROMOSOMES DNA in a higher The human body owes its structure and ability to function to one organism is organized into fundamental chemical unit: deoxyribonucleic acid or DNA. Encoded chromosomes; a in the structure of a DNA molecule are our genes, which in turn are full set is called a knitted into chromosomes. DNA is made of units called nucleotides karyotype. This light micrograph shows that come in only four different types—adenine (A), guanine (G), a human set of 46 chromosomes GENETICS I THE MOLECULES OF LIFE cytosine (C), and thymine (T); these form the letters of the genetic arranged in 23 pairs code. At a basic level, a gene is a DNA sequence that codes for a from a female (the protein. If genes are a cell’s instruction code that needs to be “read,” XX chromosomes proteins are the cell’s workers, performing a vital job in keeping our are at bottom right). cells functioning. Proteins are building blocks to make enzymes, which oversee every single chemical reaction in the human body.

Regulatory sequence Introns Exons DNA backbone Formed of alternating units of phosphate and a sugar called deoxyribose

Gene ANATOMY OF A GENE A gene consists of several regions. Those parts that contain the code to build proteins are called exons. Between them are noncoding segments called introns. Proteins controlling transcription and translation (see p.50) attach themselves to regulatory sequences.

Adenine–thymine link Adenine and thymine Thymine always form base pairs together

Adenine Guanine–cytosine link Guanine always forms a base pair with cytosine

Cytosine PATERNITY TESTS Paternity tests are based on the fact MOTHER FATHER? CHILD Guanine that half a child’s DNA comes from the mother and half from the father. The tests compare repetitive areas of noncoding DNA, which are inherited from both parents in the 66 same way as genes. A pattern of 77 similar “peaks” reveals relatedness. DNA DOUBLE HELIX Genetic instructions are packed in a double- stranded molecule. Complementary base pairs, SHARED CHARACTERISTICS OF DNA STRANDS 9 which form the crucial code, hold the strands The child’s pattern of peaks should be of DNA together by weak bonds that are easily a combination of the peaks shown by 9.3 broken when the sequence of bases is read. both mother and father. Unknown peaks Until required, the DNA is coiled tightly in the might suggest a different father. cell’s nucleus in a mesh called chromatin. 48 THE MOLECULES OF LIFE

Chromosome Mitochondrion DFNA5 gene Structure THE HUMAN GENOME Codes for the DFNA5 composed A genome is an organism’s entire genetic code. protein, which is of DNA Cytoplasm considered important molecules Starting in 1990, rival teams of scientists raced to in the functioning of decode the entire three billion bases or letters the cochlea in the inner ear, a structure required of the human genome, in the hope that once for normal hearing Cell scientists could read an individual’s DNA, a better

understanding of human health and disease might DDC gene follow. Conditions such as Alzheimer’s, cancer, and Produces an enzyme in the brain and nervous

heart disease could be tackled differently, and

system that is critical I GENETICS individually tailored drugs could become a reality. for making two of the brain’s neurotransmitters The first drafts of the human genome—the recipe for —dopamine and what makes a human—were officially completed in serotonin Nucleus 2003. It is thought that there are 20,000–25,000 genes, Acts as control KRITI gene center of cell but the total will not be confirmed for many years. Unclear role but plays a and contains What is known is that the approximate total accounts part in the development chromosomes and formation of blood for only about 5 percent of the genome. The rest of vessels and related structures, including the the DNA may be “junk” or have another purpose blood–brain barrier Supercoiled DNA apart from coding for proteins. Coils of DNA double helix are themselves twisted into a SHH gene supercoil CHROMOSOME SEVEN OPNISW gene Produces a protein Chemical staining gives chromosomes a Active in retinal cells, it called sonic hedgehog banded appearance, which can be used is needed for color in the embryo; has a to map gene locations. Chromosome vision, enabling sight at role in the formation of seven, shown here, contains about 5 the blue-violet end of the brain, spinal system, Core unit percent of the total DNA in human cells. the spectrum limbs, and eyes Package of proteins around which 2–5 turns of DNA are wrapped; also known as a nucleosome SELECTING GENDER Histone Ball-shaped Men have the final say on gender because each sperm protein carries only an X or a Y chromosome. It is unclear if gender can be influenced naturally but conditions at conception may play a part. Gender can be manipulated by using sperm sorting to enrich semen with the desired sperm, or selecting embryos during in-vitro fertilization for implantation. Choosing gender Helical repeat Helix turns 360º for for nonmedical reasons is illegal in some countries. every 10.4 base pairs X AND Y SPERM This electron micrograph has been color coded to show that semen contains virtually equal numbers of X and Y sperm.

SEX DETERMINATION X chromosome X chromosome MOTHER FATHER Y chromosome Carries about 5% What is that makes a boy a boy and a girl a girl? of our total DNA Sex is determined by specialized chromosomes known as X and Y. The X chromosome is much X XXY Y chromosome longer than the Y chromosome and carries many Holds about more genes. These two chromosomes form a pair, 2% of a cell’s total DNA sometimes called chromosome 23. In females, both chromosomes in the pair are X, resulting in XX. Males have one X and one Y, which gives them an XY identity. Genes on these chromosomes switch XXXXXYX Y on and off vital processes that make a person male or female. For example, a crucial gene on the Y DAUGHTER SON DAUGHTER SON chromosome known as SRY is responsible for a SEX CHROMOSOME BOY OR GIRL? fetus developing into a male. There are other genes Chromosome 23 is made up The gender of a baby is determined by the on the Y chromosome thought to be involved in of either two XXs (female) or father’s sperm. If the sperm that fertilizes the egg an X and a Y (male). The X has a Y chromosome, the offspring is a boy; an X male fertility. Since females have two Xs, one is chromosome has up to 1,400 chromosome produces a girl. A mother donates usually randomly deactivated in the early embryo. genes; the Y has only 70 to 200. either one of her X chromosomes to the child. 49 Cell membrane Splits as the cell HOW DNA WORKS begins the process of division DNA is the master molecule that orchestrates everything that happens in the body’s cells. One of its important functions is to replicate itself in order to create new body cells and sex cells, which allow DNA to perpetuate. Threads of spindle Connect the center TRANSCRIPTION AND TRANSLATION of each chromosome Before the DNA blueprint can be read, its instructions must ﬁrst be transcribed into a form that can be decoded. Information from the DNA HOW DNA WORKS GENETICS I HOW is copied to form an intermediate type of molecule called messenger RNA (mRNA). The mRNA then moves from the nucleus to protein assembly units called ribosomes. The mRNA acts as a template for the formation of subunits of proteins called amino acids, a process called translation. Their order is speciﬁed by lengths of mRNA three bases long called codons.

DNA strand DNA strand

mRNA strand DNA strand Strands separate RNA nucleotide

SEPARATION TRANSCRIPTION 1 Enzymes separate the two DNA strands. One of 2 Units or nucleotides of mRNA then attach these unzipped strands acts as the template for a to match the complementary molecules of the molecule known as messenger RNA (mRNA), which DNA code, forming a chain copy of the code, performs a temporary function in this process. then the mRNA and DNA chains break apart. Centriole Made of hollow Amino acid chain Bases on tRNA Amino acid carried tubules; duplicates complement bases prior to cell division Empty tRNA on mRNA by tRNA molecule molecule tRNA Amino acid molecule Organelles Specialized structures within the cell’s cytoplasm, which pull mRNA Ribosome apart during cell division strand Protein (chain of amino acids) Ribosome moves along TRANSLATION FORMING A PROTEIN THE FORMATION OF NEW CELLS 3 The message is translated into a protein 4 Amino acids link to form a protein Cells are dividing all the time, so it is crucial chain outside the nucleus at a ribosome, chain. Their sequence dictates the that genomes are copied and split correctly. where small transfer RNAs (tRNAs) collect unique 3D shape of the protein, which The average cell divides over 50 times before amino acids coded for by each codon. is crucial to the function of the protein. it reaches the end of its life.

MITOSIS Nucleus Nuclear membrane Centromere The human body constantly produces new cells for various purposes: to replace old cells lost Centromere through wear and tear or that have reached the Duplicated chromosome Single end of a ﬁnite life span; to increase numbers of Spindle chromosome cells for particular jobs such as making more PREPARATION ALIGNMENT SEPARATION 1 Before mitosis, the parent cell grows 2 The cell’s nucleus vanishes. Paired 3 The spindle’s opposing poles pull immune cells to ﬁght an infection; or simply to and duplicates its genetic material by chromosomes (chromatids) align on a apart the chromatids, doubling the grow as muscle tissue is boosted or as children forming paired chromosomes. scaffoldlike structure (the spindle). parent cell’s chromosome number. grow in stature. To produce these new cells, cells Single chromosome Nuclear Nucleus Chromosome must replicate themselves exactly—and that means membrane copying DNA instructions with extreme precision. This is done by a process known as mitosis, by which cells create a second set of identical chromosomes, temporarily doubling their DNA as they grow. Just before they divide, the two sets SPLITTING NEW CELLS 4 The new cells pinch apart. Each takes 5 Two identical cells are formed with a full complement of pull apart neatly and precisely so that each new an equal share of the chromosomes, which 46 chromosomes. The cell’s chromosomes then “rest” in a cell has its own perfectly copied blueprint. become enclosed in separate nuclei. coiled form (chromatin) in its nucleus until it divides again. 50 HOW DNA WORKS Cleavage Point at which the MEIOSIS cell begins to divide A special type of cell division is used to produce sex cells (eggs and sperm). A person inherits half their DNA from each parent, so sex cells are exceptional in that they contain only half the DNA of other cells. Both an egg and sperm cell each

contains 23 chromosomes, which come together as I GENETICS a full 46-chromosome set when they fuse to form an embryo. Sex cells are also exceptional in that the chromosomes inherited from each parent are far from identical copies. Instead, the genes on the chromosomes are shufﬂed like a deck of cards by a process called genetic recombination.

Duplicated chromosome PREPARATION 1 Parent cells in the testes or ovaries grow, doubling in size and duplicating their genetic material by forming double chromosomes. Matching pairs of chromosomes PAIRING 2 Identical copies of maternal and paternal chromosomes pair up and are interwoven in the process of recombination, during which they may swap genes or pieces of chromosome.

Matching pairs of chromosomes

FIRST SEPARATION 3 The paired chromosomes (sister chromatids) are then pulled into two new daughter cells as the parent cell cleaves.

Duplicated chromosome

Chromosome Contains most of the cell’s genetic material TWO OFFSPRING 4 The daughter cells are genetically nonidentical to the parent cell, but each has a set of 46 chromosomes Centromere that must be halved to make a sex cell. Single Point at which the chromosome chromosome pair splits to form single chromosome

GENETIC RECOMBINATION SECOND SEPARATION Spindle Genes are shufﬂed randomly during Duplicated maternal Duplicated paternal 5 The nucleus disappears and the spindle reappears the “pairing” stage of meiosis by a chromosome chromosome to pull the sister chromatids apart into four new cells. process known as recombination. There is no doubling of genetic material at this stage. Each cell has two copies of every chromosome—one from each Chromosome parent. During recombination, pairs of these chromosomes come together in a process called “crossing over.” The pairs intertwine, exchanging pieces of DNA.

CROSSING OVER Chromosome pairs exchange as little as a STAGE 1 STAGE 2 FOUR OFFSPRING few genes, or as much as a whole arm in Genetic material Genetic material Four new cells, each with 23 chromosomes, 6 Nucleus this genetic lottery, ensuring that gene from paternal from maternal are created. Each of these cells is genetically combinations are mixed up in sex cells. chromosome chromosome unique, containing a random mix of the genes from the original chromosomes (see panel, left). 51 PATTERNS OF INHERITANCE How can people share a great-uncle’s nose or a quirky sense of humor? Patterns of gene inheritance help us understand this—although nurture also determines how such traits are expressed. THE FAMILY TREE DNA is shufﬂed randomly from one generation to the next, but there are rules and basic mathematics that reveal a lot about genetic relationships. A person shares half of his or her DNA with each parent, and each of the parents has half of each of their parents’ PATTERNS OF INHERITANCE GENETICS I PATTERNS genes. This means that an individual shares a quarter of the genes with each grandparent. Although siblings are different from each other, they share about half their genes. The closest genetic relationship is between identical twins, in whom 100 percent of genes are the same. In contrast, only 12.5 percent of genes are shared with a ﬁrst cousin.

MATERNAL MATERNAL PATERNAL PATERNAL GRANDMOTHER GRANDFATHER GRANDMOTHER GRANDFATHER

MOTHER FATHER

Genes shared with Genes shared with maternal grandmother paternal grandfather

Genes shared with Genes shared with maternal grandfather CHILD paternal grandmother HUMAN DIVERSITY SHARED GENES Humans are amazingly diverse, a fact that is due to both genetic The share of common genes is halved in each new inheritance and variation in generation. Every person inherits half of the genes from environmental factors. each parent, and passes on half of these to the children.

ATTACHED OR SINGLE- AND MULTIPLE-GENE Recessive allele for Dominant allele for UNATTACHED attached earlobes unattached earlobes EARLOBES? INHERITANCE Whether earlobes hang A gene comes in different forms (alleles) and, for any MOTHER FATHER free or attach to the sides of the face is particular gene, one allele is inherited from each parent. thought to hinge upon The gene’s expression in the offspring depends on the a single gene, although some scientists have combination of alleles, and whether or not the gene recently suggested that governs one trait by itself or works in combination with the issue is more others. The simplest type of inheritance is where one complex than that. gene is responsible for one trait—for example, some diseases, such as Huntingdon’s, are carried on single genes. Typically, an allele can be dominant or recessive. CHILDREN When there is a dominant copy from one parent paired with a recessive copy from the other parent, the All the children have dominant one will manifest—only one copy is needed. unattached earlobes The recessive trait is expressed only when a person DOMINANT AND RECESSIVE GENES inherits two copies of a recessive allele. But many traits, This chart shows a possible combination of genes in the such as eye color, are governed by many genes and so, inheritance of earlobe shape. To manifest the recessive trait, a person needs two recessive alleles for this gene. Here, the although their inheritance works on the same principles children have unattached lobes but carry the recessive trait, as single inheritance, it is harder to predict the outcome. so some of their children could have attached earlobes. 52 PATTERNS OF INHERITANCE SEX-LINKED INHERITANCE Some genes for non-sex functions are on the sex chromosomes X and Y. How they are passed on depends on which of these chromosomes they are located, and also whether the alleles are dominant or recessive on that chromosome. For example, because males are XY and carry only one X, they will inherit any X-linked genes and pass these on to all of their daughters, but not their sons. The daughters will all be “carriers” if the allele is recessive, and affected if it is dominant. Females have two Xs, and in I

any given cell one is randomly GENETICS deactivated, so they rarely manifest X-linked recessive disorders because they usually

have a normal backup copy of the allele active in other cells.

COLOR BLINDNESS This largely red image with the number 74 appearing in green is a classic test for color blindness. Color blindness is an X-linked recessive disorder, so it is much more common in men than women.

GENES AND THE ENVIRONMENT Many of the traits people have are honed by a complex, often shifting interchange between genes and environment—the “nature versus nurture” debate. Traits such as personality, intelligence, and height are on a continuum. How people turn out depends on the genetic hand dealt to them by their parents as well as their external environment, such as family upbringing, socioeconomic status, nutrition, physical circumstances, and emotional environment. Many diseases, such as depression, heart disease, schizophrenia, and cancer, may have both genetic and environmental components. So genetics might make someone susceptible to a condition, then negative or positive environmental factors can tip the balance either way. Studies of identical twins have probed the question of what proportions of particular TRANSGENERATIONAL INHERITANCE traits are heritable.

In recent years, scientists have found that the pattern of how genes INHERITING INTELLECT? are switched on and off in the body in response to the environment About half the variation in human IQ —the science of “epigenetics”—is also inherited. This may be down to genetics. But whether or not a child’s genetic promise is means that changes in gene expression from our fulfilled depends on nurture. A child grandparents in response to their environment can with a less fortunate hand may make up be inherited. For example, studies have suggested the difference in a good environment. that famine affects the expression of certain genes, which is thought to cause obesity in subsequent generations. ORIGINS OF CHARACTER TRAITS Methyl group A hydrocarbon, which ENVIRONMENTAL INTERACTIONAL GENETIC attaches itself to DNA; SWITCHING OFF GENES huge numbers of these • Specific language (entirely) • Height • Blood group (entirely) Genes can turn off when can silence a gene • Specific religion (entirely) • Weight • Eye color (entirely) methyl groups attach to • Specific culture (entirely) • Intelligence • Hair color (entirely) bases. Heavily methylated • Sensitivity to • Personality • Certain genetic diseases, areas of DNA have been environment-based stresses • Certain multifactorial such as Huntingdon’s (entirely) shown to be inactive. This like radiation (mostly diseases like heart disease • Baldness (mostly genetic) pattern of methyl groups environmental) can be inherited.

53 GENETIC PROBLEMS GENE LEVEL GENETICS AND INVESTIGATIONS Faulty genes can be inherited, can spontaneously mutate in an embryo, or can accumulate mutations after long DNA replicates itself millions of times and with exposure to mutagens such as UV amazing accuracy over a lifetime but, sometimes, from the Sun, radiation, or tobacco. G things can go wrong. E N E C H WHERE GENETIC PROBLEMS ARISE R O When there is a change in DNA (due to an internal error in M O the normal functioning of a cell or an attack from an external S O environmental cause, known as a mutagen), problems can arise on M A three main levels. In the ﬁrst level, a change in a gene affects the L

protein for which it codes. The next

level sees a change in the number of L

A CHROMOSOMAL

chromosomes. Thirdly, problems can M LEVEL

O Errors can occur occur when there are alterations in S

U O when chromosomes

several genes plus environmental M L

L A are divided up during

O R

T N O

triggers. There is a fourth level, R mitosis and meiosis

I C O H

T (see pp.50–51), such as

F I M

affecting mitochondrial DNA, C

A L the inheritance of an

C A but this is unusual compared

T I incorrect number

O R with the other three levels. of chromosomes.

R O

I T

A C

L A MULTIFACTORIAL LEVEL F

I Some diseases are inﬂuenced by MITOCHONDRIAL LEVEL

T mutations in a number of genes Mutations can occur in the DNA

L M I

T U plus environmental factors contained in the cell’s mitochondria—

O C

H M O that affect susceptibility. For N the structures that give cells the D R I A example, Alzheimer’s disease L energy they need to work. Their DNA and breast cancer are codes for proteins that are needed to multifactorial in their origins. keep mitochondria working properly.

MUTATIONS DIFFERENT TYPES OF GENE MUTATION Any permanent alteration in the code of a DNA sequence is known Gene mutations can be caused by particular types of errors. The way in which they as a mutation. It can be as small as a one-“letter” change in a gene affect the gene’s function depends on if and how they alter the “reading” of the or as large as a chunk of chromosome. The effect of a chromosomal DNA code, and if any subsequent changes affect the protein made by the gene. mutation depends on the size and location of the structural change and whether any DNA is lost. It usually occurs either in the sperm TYPE OF MUTATION CORRECT CODE FAULTY CODE or eggs, or early in embryonic development. Gene mutations can be inherited or they can occur spontaneously in an embryo. But, often, Frameshift mutation CAT CAT CAT CAT ATC ATC ATC ATC DNA is read in “frames” of three letters that they occur in body cells when the intricate system for replicating translate into amino acids. A mutation shifts Three-letter frame Sequence shifted one DNA slips up somewhere. A gene mutation can have a negative this frame and will change the amino acids. frame to the right, so CAT becomes ATC effect if it impairs the normal functioning of a gene. Deletion mutation CAT CAT CAT CAT CTC ATC Any small or large loss of the DNA bases “A” removed A large or A portion The DNA or letters of a gene is a deletion. small part of a of the sequence chromosome chromosome is reversed, can be deleted. has been but no DNA Insertion mutation CAT CAT CAT CAT CAT CAT ACA TCA doubled. is lost. Any insertion of extra DNA, from a single unit (nucleotide) to larger pieces, could “A” inserted potentially disrupt the function of a gene.

Increased repeat mutation TAG GCC CAG GTA TAG GCC CAG CAG ABNORMAL This is a type of insertion mutation that adds in a short repeating DNA sequence CAG frame repeated NORMAL NORMALABNORMAL NORMAL ABNORMAL that can impair gene function. DELETION DUPLICATION INVERSION A chromosome segment A segment of chromosome A chromosome can break Missense mutation CAT CAT CAT CAT CAT CCT can break off. The effect on can be copied more than in two places, and the “lost” One letter of the code is swapped for function depends on the once erroneously. That portion can be reinserted, another, introducing the sequence codes “C” incorrectly added amount of genetic material segment may then be but the wrong way around. for a different amino acid than intended. instead of “A” deleted and its function. duplicated several times. Usually, no DNA is lost. 54 GENETIC PROBLEMS AND INVESTIGATIONS

GENETIC COUNSELING MEDICAL FAMILY TREE To assess the risk of A person with a genetic disease in the family, such developing an inherited as cystic ﬁbrosis or some cancers, might visit a disorder, a genetic genetic counselor to seek advice on the risk of counselor takes a detailed medical history of a developing the disease or passing it onto their patient and his or her children. A genetic counselor offers guidance on family’s health to produce a family tree like this one. ways to prevent the disease if there are KEY environmental components, testing family members DIED OF AFFECTED BY UNKNOWN if appropriate, or treatment options, if available. CANCER CANCER

Pregnant women may visit genetic counselors if NOT AFFECTED they have had an abnormal prenatal-test result. BY CANCER Parents of children with medical or learning difﬁculties where a genetic condition may be involved may also attend for an assessment. A genetic counselor can also give information on the

chances of an unborn child carrying a potentially I GENETICS problematic gene. The genetic counselor informs the mother-to-be of what a genetic test result during pregnancy means and outlines the options for treatment and management of the condition.

12 KEY DIED FROM DIED FROM AFRICAN- BOWEL CANCER BOWEL CANCER AMERICAN 10 ASHKENAZI JEW EUROPEAN- 8 AMERICAN HISPANIC 6 MEDITERRANEAN

A PROBLEM GENE A PROBLEM 4

2 PERCENTAGE CHANCE OF CARRYING CHANCE OF CARRYING PERCENTAGE (0%) (0%) (0%) 0 CYSTIC FIBROSIS SICKLE-CELL ANEMIA ? GENETIC DISORDERS AND ETHNICITY Some ethnic groups are much more likely to carry problem genes than others. This graph shows that Americans of African descent have a much higher DIAGNOSED WITH THIS WOMAN IS chance (9 percent) of carrying sickle-cell anemia ENDOMETRIAL VISITING A GENETIC than any of the other ethnic groups tested. (UTERINE) CANCER COUNSELOR

GENETIC SCREENING AND TESTING Genetic tests for disorders are performed early in pregnancy, or in “SAVIOR” SIBLING newborns, to catch disorders that can be treated early in life (such as phenylketonuria), or later in life to screen for disease-susceptibility Occasionally, embryos are selected of being disease-free themselves for implantation to create “savior and being able to provide a tissue genes (such as BRCA1 for breast cancer) before any symptoms have siblings” for existing children with match for their sibling. When these occurred. Prenatal tests include amniocentesis, which involves severe, life-threatening disorders, children are born, stem cells from taking fluid from the amniotic sac, which contains free-floating such as Diamond blackfan anemia. their umbilical cords or bone cells from the fetus. These cells are examined for chromosomal Using preimplantation genetic tests, marrows may be used to treat they are chosen on the basis their older siblings. abnormalities, and can pick up certain conditions, for example BORN TO CURE Down syndrome. In 2003, the parents of Zain Hashmi (pictured) won a legal battle in PREIMPLANTATION TESTS the UK to attempt Where the risk of a serious to conceive a tissue- genetic condition is high, tests matched healthy may be carried out in some sibling for Zain to help countries on embryos fertilized cure his debilitating in a laboratory to select a healthy beta-thalassemia. embryo for implantation. 55 THE EVENTS THAT LEAD UP TO THE BEGINNING OF A PREGNANCY ARE MORE COMPLEX THAN THEY MAY APPEAR. IN HUMANS, SEX STARTS WITH AN INTERPLAY BETWEEN SENSORY STIMULI AND HORMONES, WHICH RESULTS IN ATTRACTION. DESIRE, AROUSAL, AND ORGASM FOLLOW, AS THE GENITALS AND THE BRAIN CONTINUOUSLY COMMUNICATE WITH EACH OTHER VIA THE NERVOUS SYSTEM. HUMANS DIFFER FROM MOST OTHER ANIMALS IN HAVING SEX FOR PLEASURE AND NOT JUST FOR PROCREATION. THE NEED TO AVOID THE UNWANTED PREGNANCIES THAT OFTEN ARISE FROM THIS PLEASURABLE ACT HAS LED TO THE DEVELOPMENT OF VARIOUS FORMS OF CONTRACEPTION. THE SCIENCE OF SEX THE EVOLUTION OF SEX The word “sex” is used to distinguish males from females, and can also mean the act of reproduction. Evolution is involved in both of these definitions of sex, allowing species to adapt to their environment and maximize the spread, and therefore survival, of their genes. WHAT IS SEX? The sex of a human is obvious from the external genitalia, but for many animals gender can only be determined by either the sex chromosomes or the size of the sex cells (gametes). Females usually have the larger sex cells (eggs) and males the smaller (sperm), yet early in the evolution of organisms sex cells of the same size combined to produce offspring. Differing sizes are thought to have evolved because some gametes found it advantageous to become smaller and quicker, while others had to enlarge to produce offspring of the same fitness.

THE EVOLUTION OF SEX OF SEXTHE SCIENCE I THE EVOLUTION Egg Large and relatively immobile cell Sperm Small cell trades size for swimming ability

RELATIVE SIZE OF SEX CELLS Some species, such as yeast, still reproduce by the fusion of equal-sized gametes, but many organisms that evolved more recently have much larger female sex cells than male sex cells.

WHY HAVE SEX? The primary reason for sex is to make new genetic copies of ourselves—offspring are the only way for our genes to survive. Many animals will only have sex during a female’s fertile period, yet humans, and some other species such as dolphins, also have sex for pleasure. This human instinct may have evolved to help bond men and women as a couple (“pair bonding”), which would have been vital in the past when it was GENETIC COPIES SEX FOR PLEASURE Offspring are a way of a harder for one person to look after a baby. Humans have engaged in parent’s genes surviving, Sex triggers the release of oxytocin from the sex for pleasure for much of their yet two parents can each evolutionary history. Arstistic give only 50 percent of their pituitary gland; this hormone is thought to depictions are common, such as genes to a child. play a key role in pair bonding. this ancient Greek erotic scene.

SPERM COMPETITION HERMAPHRODITES Only the female can guarantee that a baby is hers; Humans born with dual genitalia, males have no such security. To ensure that they due to rare hormonal disturbances, have a better chance of fertilizing the female’s egg, can appear to be both male and males must ensure that their sperm are fitter than female. Yet they cannot use both a potential rival’s. Certain animals, including some sets of genitals to reproduce. True hermaphrodites have both male butterflies, produce two types of sperm; one that SURVIVAL OF and female reproductive organs and fertilizes and another that helps it along (accessory THE FITTEST are able to fertilize one another. sperm). Producing more sperm can also help to There are normally This is an evolutionary advantage ensure successful fertilization. Promiscuous species over 15 million sperm for animals such as slugs or snails in per milliliter of human which individuals are solitary and produce more sperm and therefore have larger semen. Each sperm rarely meet, so a single encounter testes. Humans are more promiscuous than some races the others to be the one to fertilize carries double the chance of other apes, such as gorillas, so male humans have the egg, and only the successful reproduction. proportionally larger testes than male gorillas. fittest sperm will win. 58 THE EVOLUTION OF SEX ASEXUAL REPRODUCTION Some organisms reproduce asexually by making copies of themselves. There are a variety of different methods of asexual reproduction CLONING (see right), but each process bypasses the need Some animals, such as corals, can reproduce for fertilization, making it far quicker to produce by producing exact offspring than by sexual reproduction. Offspring genetic copies (clones) of themselves. Corals are therefore genetically identical to their parents. can also use sexual Reproducing asexually does not create the genetic reproduction. I THE SCIENCE OF SEX variety ideal for overcoming environmental change, but for many organisms it is a successful strategy. It is best suited to organisms that face little competition from more adaptable species or REGENERATION that live in environments that see little change. This is the result when an animal forms from a broken-off fragment ADVANTAGES AND DISADVANTAGES of a parent. Starfish can develop in this Asexual reproduction is most common in single-celled way, but only if part of organisms, such as bacteria, but many plants and fungi, as the center is included well as larger animals such as the whiptail lizard, use it too. in the fragment.

Advantages • No need to look for a mate • Energy can be devoted to making new copies • Fast reproductive method • Parent genes are not diluted PARTHENOGENESIS by those of a partner Parthenogenesis is the development of an Disadvantages • No genetic variation offspring from a female (bad genes persist) egg that has not been • No adaption to environmental change fertilized by a male. Whiptail lizards reproduce in this way.

SEXUAL REPRODUCTION Haploid sex cells sperm and egg cells; Sexual reproduction occurs when a male and female each have one set of combine the genes contained within their sex cells Meiosis 23 chromosomes Fertilization through fertilization. This does not need to involve penetrative sex: some ﬁsh sex cells combine in the Multicellular organism Diploid zygote water, outside the female’s body. All sex cells are capable of producing contains 2 sets of haploid, meaning they have half the correct number sex cells 23 chromosomes of chromosomes; they then combine to form a diploid cell containing the full complement. Reproducing Mitosis sexually creates offspring with huge genetic variety, COMBINING SEX CELLS enabling natural selection to occur. As environments Parent cells with 46 chromosomes divide by meiosis to produce haploid sex cells with only 23. One sex cell from change, individuals with genes that help in their each parent combines to produce a diploid offspring cell; new environment adapt and survive; those without this divides by mitosis to form an organism (see pp.50–51). them die off. This makes organisms that reproduce ADVANTAGES AND DISADVANTAGES sexually more likely to be Sexual reproduction is currently a major form of able to evolve over time. reproduction among organisms. It is primarily, but not exclusively, seen in members of the animal kingdom.

Advantages • Two parents create genetic variation LACTOSE TOLERANCE • Species adapt easily to changes in their Humans only started consuming dairy environment produce in recent evolutionary history. In • Less chance of genetic disease early societies, some people had genes that allowed them to digest lactose—the sugar Disadvantages • Time must be invested in ﬁnding a mate found in milk. When they began to farm dairy animals, these people thrived and their • Fertilization is not always successful lactose-tolerant genes became prevalent. In • Parents can only pass on 50 percent societies that have not traditionally farmed of their genes dairy animals, lactose intolerance is common. 59 POINT OF FERTILIZATION This electron micrograph shows tadpole- like sperm surrounding the much larger egg. Fertilization, which occurs in one of the fallopian tubes, takes place when the head of a sperm penetrates the egg and fuses with its nucleus.

ATTRACTIVENESS Sexual attraction is often assumed to be an inexplicable instinct, yet the interaction of many factors lies behind this seemingly mysterious chemistry. Chemical cues, thought to be pheromones, add to hormonal effects, visual cues, and other as yet unidentified factors, which lead us to be attracted to others. HOW MATING SYSTEMS POSITIVE ASSORTATIVE MATING AFFECT APPEARANCE Positive assortative mating is the inclination of The environment in which animals live has had organisms to select a mate that displays similar a large impact on the development of their mating attributes to themselves. Humans, subconsciously, systems, which, in turn, have strongly shaped their choose their partners in this way—people who are appearance. In environments that support many similar in appearance and intellect often tend to animals, a large group of females may be guarded form couples. This instinct may have evolved in THE SCIENCE OF SEXTHE SCIENCE I ATTRACTIVENESS by a single male. These males are often larger than humans because it the females and have developed weapons, such as promotes long-term, large antlers, with which to fight other males for stable relationships. possession of the females. When the environment These were necessary does not support a large group, and there is no in early human advantage in fighting, some males attract females evolutionary history using showy physical attributes, such as colored because offspring feathers, to signal that they are fit to mate with. had a better chance of survival SHOWING OFF If a peacock’s tail has more if both parents eye spots than a rival’s, it signals were able to look to the female that the male is genetically fit, and will pass after them. on good genes.

PHYSICAL SIMILARITIES WEAPONS It is easiest to observe PROPORTIONAL BODY SIZES Male red deer compete positive assortative mating In promiscuous mating systems, or those to mate with females. If a when looking at the physical where long-term pair bonds form, such competing male is not scared similarities, such as race or as in humans, males and females are off by a rival’s appearance, body height, between similar in appearance. ﬁerce ﬁghting ensues. partners in a couple.

THE MENSTRUAL CYCLE AND MATE CHOICE 400 “CONCEALED” OVULATION 350 A study shows how lap dancers Hormone ﬂuctuations during the menstrual cycle affect how women rate get better tips when they 300 the attractiveness of men. In their most fertile period (around ovulation), ovulate. This suggests that 250 subtle changes in behavior women tend to be attracted to men with highly masculine attributes who around ovulation enable men 200 are most genetically different from them. This attraction is subconscious to determine whether women 150 are in their fertile phase. and thought to be because these men will produce offspring who are the 100 most genetically ﬁt. Yet at other phases of the menstrual cycle, women tend

DOLLARS EARNED PER SHIFT 50 to be attracted to men who are genetically KEY 0 WOMEN NOT ON ORAL similar and less masculine, but more likely MENSTRUAL FERTILE LUTEAL CONTRACEPTIVES to enter into a partnership and look after PHASE OF CYCLE WOMEN ON ORAL CONTRACEPTIVES any offspring. It seems that women have therefore evolved to try to mate with genetically fit men, and form long-term THE EFFECTS OF ORAL CONTRACEPTIVES partnerships with those perceived to The oral contraceptive pill usually suppresses ovulation, meaning that have a more nurturing nature. the subtle cues that attract women to masculine, genetically dissimilar men during ovulation are disturbed. The long-term effects of this are not yet known. However, it might lead women to be more likely OVULATION AND ATTRACTION to produce offspring with men that are genetically similar to them, This colored scanning electron micrograph which could lead to less fit offspring. It could also have implications shows the moment of ovulation when the egg (pink) is released. Around this time, women are for relationship stability, because when a woman comes off oral subconsciously attracted to men who are most contraceptives, she may start to view her partner in a different way. genetically fit and suitable to father offspring. 62 ATTRACTIVENESS PHEROMONES Pheromones are chemicals that animals of the same Nasal septum species emit to communicate with one another. Some animals use them to mark an area of territory. Ants use them to set trails to guide other ants to food or Vomeronasal alert them of danger. Pheromones play a role in organ mating. In many species, possibly including humans, I THE SCIENCE OF SEX Oral cavity they signal that a female is ready to mate; one study COLORED ELECTRON MICROGRAPH OF showed that men were more attracted to the clothing FETAL VOMERONASAL ORGAN of ovulating women. Pheromones may also account VOMERONASAL ORGAN for people being drawn to potential partners who are Many animals sense pheromones using the vomeronasal organ within the nose. In humans, this genetically different from themselves, allowing for organ is only present during the fetal period; after maximum genetic diversity of any potential offspring. CROSS SECTION OF FETAL NASAL CAVITIES this, it is thought to degenerate during development.

FACIAL SYMMETRY Facial features are rated as attractive based on whether they are seen as more masculine, for a man, or feminine, for a woman. Subconsciously, facial symmetry has an effect on the percieved masculinity or femininity of a face. People with more symmetrical faces, and those with faces characteristic of their sex, report fewer health problems, so facial characteristics may be a way of signaling this ﬁtness to others. Only high-quality males or females are symmetrical and are seen to have more masculine or feminine facial features.

FEMALE MALE HAZDA EUROPEAN

HIGH LOW HIGH LOW HIGH AND LOW FACIAL SYMMETRY These composite faces, made from photos of people from two ethnic groups, represent high and low symmetry for each group.

100 90 80 70 60 50 40 30

LINES OF SYMMETRY OR FEMININE MASCULINE 20 To judge whether a face AS MOST CHOSEN PERCENTAGE 10 is symmetrical, people 0 assess the distance from FEMALE MALE FEMALE MALE the middle of the face to HADZA FACE EUROPEAN FACE points such as the eyes, margins of the face, and ATTRACTIVENESS RATING KEY HIGH SYMMETRY edges of the nose. In this study, those with high- symmetry faces are judged LOW SYMMETRY to be more masculine or feminine than those with low-symmetry faces. 63 THE SCIENCE OF SEX I DESIRE AND AROUSAL DESIRE AND AROUSAL Desire and arousal are the conscious preludes to sex. To experience these basic FLUCTUATIONS IN DESIRE human instincts requires complex interactions between the brain, nerve networks, and Levels of desire fluctuate throughout hormones, which coordinate the body’s response to sensory and physical stimulation. life. These fluctuations have many causes, including hormonal and psychological factors. For women, Somatosensory Genital area WHAT TRIGGERS DESIRE? cortex levels of desire regularly fluctuate Sexual desire is usually instigated by the combined The body’s sensory Breast area with the short-term hormone system, located effect of numerous sensory desire cues. Sight, smell, along the parietal variations of the menstrual cycle. lobe of the brain Lips and The hormone testosterone is also sound, touch, and even taste all help trigger desire. tongue area Stimuli are detected by the peripheral nervous linked to long-term desire in both system, which transmits nerve impulses to the Hypothalamus men and women. Feelings of desire Coordinates sensual brain’s somatosensory cortex where we “feel” stimuli to trigger increase rapidly after puberty, when these senses. Imagination and thoughts of reward, desire and arousal testosterone levels first rise, although involving several areas of the brain collectively both will decline with age. Levels SECRETION In men, testosterone known as the limbic system, of testosterone in men peak in the is secreted by cells also play key roles in desire. BRAIN mid-thirties and slowly decline; in in the testes (pink in this light micrograph); Once the senses and Lips and Lips and women, levels of all sex hormones women produce it imagination are stimulated, tongue tongue fall sharply after menopause. in their ovaries. impulses from the relevant Breasts 28 0 DAYS areas of the brain travel to Bleeding begins the hypothalamus where they During a period, sexual desire is often at its lowest point are processed, resulting in Genitals Genitals Premenstrual stage 6 feelings of desire and arousal. Fertile time Around ovulation (day 14), women KEY EROGENOUS ZONES experience a MENSTRUAL CYCLE KISSING These are densely packed with sharp rise in Feelings of desire and A kiss is a highly effective trigger for nerves that detect touch. The areas desire arousal generally increase desire. Involving lips and tongue (key of the brain that process signals around the time of erogenous zones), it requires close from these nerves are proportionate 12 ovulation, which is when physical proximity and activates in size to the number of nerve women are most likely sensations of touch, taste, and smell. MALE endings in each erogenous zone. FEMALE 15 to become pregnant.

SEXUAL RESPONSE KEY AROUSAL PATHWAYS In both men and women, arousal is SYMPATHETIC controlled by impulses traveling between NERVE FIBERS Signals are carried between the brain and genitals by sensory nerves the spinal cord and the brain. A complex PARASYMPATHETIC and nerves of the parasympathetic and sympathetic nervous system interaction of nerve signals leads to arousal NERVES FIBERS that can culminate in orgasm. To prevent PUDENDAL NERVE (part of the autonomic nervous system, which regulates internal arousal at inappropriate times, the pons processes). The signaling is coordinated by the hypothalmus, (located in the brainstem) sends inhibitory signals via the sympathetic nerves. which sends signals down the spinal cord to interact with the parasympathetic nerves that carry signals to the genitals to trigger Hypothalamus BRAIN SIGNALS arousal. Sensory nerves travel back from the genitals to the spinal 1 Impulses from the hypothalamus pass down the spinal cord to cord and relay messages of sexual pleasure. These act directly on Pons instigate arousal in the genitals; the parasympathetic nerves to heighten genital arousal, including pleasurable sensations are later Spinal relayed back to the brain. Inhibitory engorgement of erectile tissue, and also signal to the brain to boost cord signals are sent by the pons. arousal. This builds until a tipping point is reached, when the sympathetic nerves take over and cause orgasm. INHIBITORY SIGNALS 2 Sympathetic nerves from the spinal cord travel to the genitals. They carry ENGORGEMENT impulses from the pons that prevent unwanted arousal. Signals from When arousal begins, the erectile tissue, which is found the hypothalamus can overcome in the man’s penis and the clitoris and labia in the this when arousal is appropriate. woman, starts to fill with blood in response to signals STIMULATORY SIGNALS sent along the parasympathetic nerve fibers. As the 3 Arousal impulses from the penis becomes engorged, it becomes erect and hard, brain are channeled through ENGORGEMENT which is necessary for penetration. Engorgement of parasympathetic nerves. These 4 Parasympathetic the clitoris and labia heightens the pleasure a woman leave the spinal cord via one of nerve fibers that travel experiences from sex. two routes: some travel directly to the genitals cause to the genitals; others are carried the erectile tissue Veins drain Compressed within the pudendal nerve. to engorge. blood veins cannot normally drain blood SENSATION 5 The pudendal Corpus Artery nerve fibers sense cavernosum dilates touch on the clitoris Sympathetic and labia and relay nerve fibers this back to the brain connect to via the spinal cord. vagina and uterus

Uterus

Corpus cavernosum Corpus and corpus spongiosum FLACCID ERECT spongiosum PENIS PENIS ﬁll with blood MALE ERECTILE TISSUE During arousal, arteries that supply the penis dilate, Sympathetic allowing excess blood to engorge the spongy erectile nerves tissue. Veins become compressed, preventing blood from leaving the penis; this maintains the erection.

Clitoris Ischiocavernosus muscle

Labia minora

Vagina Corpus cavernosum Clitoris BUILDING Bulb of vestible Labia 6 TO ORGASM Parasympathetic nerves NONERECT ERECT Erectile tissue TISSUE TISSUE outside the pudendal nerve engorges with blood sense the sexual organs FEMALE ERECTILE TISSUE stretching as they engorge Erectile tissue in women is similar to that in men, and relay pleasurable Parasympathetic fibers but the volume is far smaller. The clitoris becomes within pudendal nerve sensations back to the brain. erect when blood engorges the corpus cavernosum. travel directly to genitals The sympathetic nerves that The external genitalia (vulva) also become engorged supply the genitals will with blood during arousal. eventually take over to instigate orgasm. 66 THE SCIENCE OF SEX I THE ACT OF SEX stimulated as the penis moves intoandoutof asthepenis stimulated hundreds ofsensorynerve endings,whichare contains penis) (glans urethra. Theheadofthepenis helplubricatethemale glands, as thebulbourethral inthemalegenitalareas,such accessory sexglands lubricatethepassage; inthevagina from glands easilyandpainlessly.into thevagina Secretions erectandtohave enoughlubricationtopass to be Thisrequiresthepenis bythepenis. of thevagina Sexual intercourseusuallyinvolves penetration INTERCOURSESEXUAL as ameans ofreproduction. other animals,by contrast, use sex purely pleasure Most andemotionalbonding. enable conception aswell asfor physical Humans engage insexual intercourse to THE ACT OFSEX LEVEL OF AROUSAL resumedfor atime. anderectioninthemancannotbe relaxes wherethe erectiletissue Afterorgasmistherefractoryphase, occurs. isshort,when orgasm for varyinglengthsoftime.Thethirdphase last isatitsgreatest.Thesetwo phases its maximalsizeandarousal swollento whentheerectiletissuehas phase, Second istheplateau resultinginlubricationandswellingoferectiletissue. arousal, causes first isexcitement,whereeroticphysicalormentalstimulation menandwomen.The ofsexinboth phases There arefourclassic THE PHASESOFSEX Excitement phase Plateau phase Plateau phase Excitement phase shape duringpenetration. It can assume aboomerang lies outsideofthevagina. sex shows thepenismostly This MRIscan taken during PENETRATION by men than women. by menthan achieved moreeasily in orgasm—astate usually culminates pleasure buildsand Sexual and vagina. endings intheclitoris nervestimulates movement also This the vagina. Orgasm TIME phase Refractory phase Refractory Seminal vesicle if sexistimedto coincide withovulation. genital tract. Thiscan lead to conception seminal fluidfrom themale to the female orgasm, whichresults inthetransfer of genital areas duringsexeventually leads to Stimulation ofnerve endingsinthe PROCESSSEXUAL Paired glands secrete a secretes amilky, Bulbourethral gland urethra duringarousal slightly alkaline Exit to bladder nourish sperm secrete afluid clamps during Vas deferens lubricating fluidinto into ejaculate Paired glands sperm from Gland that Transports that helps Prostate fluid into ejaculate testes to Bladder orgasm urethra vary from theclassic curve. response curve (purple) can some women’s sexual phases inasimilar way, but pass through each ofthese sex (green). Most people curve ofthefour phasesof This graph shows theclassic AROUSALSEXUAL KEY CLASSIC CURVECLASSIC FEMALE a stable pairbondafter sex(seep.58). It isthoughtto be oxytocin that helps couples form pregnancy, labor, breastfeeding, andalsorelationships. actions, oxytocin haseffects onsexualbehavior, orgasm, organs suchasthebreasts anduterus. gland into thebloodsteram, where itistransported to Oxytocin isahormonethat isreleased from thepituitary THE LOVE HORMONE into thebloodsteram. for storage andrelease to thepituitarygland before beingcarried in thehypothalamus oxytocin issynthesized Most ofthebody’s OXYTOCIN RELEASE anus duringorgasm Perineal muscles Contract to close Hypothalamus Pituitary gland and prevent defecation ejaculate; butpath ofurineis Dual conduit for urineand blocked duringorgasm

Among manyother Urethra THE ACT OF SEX I THE SCIENCE OF SEX 67 Fallopian Fallopian tube Ovary Uterus JOURNEY OF SPERM micrograph This colored sperm in the female shows Mucosa tract. reproductive a ﬂuid secrete (purple) cells sperm. and protect coat to Walls of vagina of vagina Walls to stertch accommodate penis Vagina

EXPULSION action the cumulative Finally, 3 of these muscles expels the expels of these muscles the end of the semen from it high in the penis and deposits sperm must here, From vagina. the through progress to swim tract. reproductive female EJACULATION In males, the rhythmic contraction of muscles in the lower pelvis, such as the bulbospongiosus muscle at the base of the penis, propels semen through the genital tract. Semen comprises sperm and fluid from the vas deferens, as well as fluid secreted by the accessory sex glands, which include the seminal vesicles, prostate, and bulbourethral glands. Semen is alkaline to counteract the acidity of the vagina and enable sperm to swim. It is ejected between contraction of the first and seventh orgasm into the top of the vagina. Sperm will only be able to fertilize become an egg once they have activated in a process called capacitation (see p.80). MUSCULAR CONTRACTIONS coordinated Continued

contractions of muscles in the muscles of contractions but their pleasure, cause genitals sperm convey main function is to accessory past the ﬂuid-secreting and tract in the genital sex glands the urethra. then into 2 Bladder Bladder entrance closes Seminal pool forms and clots in upper vagina Clitoris Clitoris and labia engorge Vaginal Vaginal muscles contract Rectal Bladder sphincter sphincter contracts SPERM RELEASE in the testes made are Spem that

Penis Epididymis of sperm storage Site Testis are stored in the epididymis and the stored are the During orgasm, deferens. vas of these contraction muscular this sperm forces structures deferens. the vas up through 1 bone Pubic SPERM DURING FEMALE ORGASM Semen clots in the and upper vagina, sperm must swim past continue to Orgasmic the cervix. help may contractions and open the cervix semen toward move tubes. the fallopian Orgasm is the intense climax of sexual pleasure that is caused by activation of the sympathetic (see pp.64–65) nerves the sacralthat area of the spinal leave cord, in the lower back. These nerves to muscles within the lower travel pelvis and cause them to rhythmically also cause contract. Sympathetic nerves the muscles at the exit of the bladder to close, so that urination does not simultaneously occur during orgasm. The number of muscle contractions can but they vary, usually total between 10 and 15 perorgasm. ORGASM BIRTH CONTROL Birth control has been used for generations as a means of avoiding unwanted pregnancies. Today there is a range of methods available, and most people will ﬁnd something to suit them. THE IMPORTANCE OF BIRTH CONTROL For many people, birth control simply allows them to have sex without the fear of pregnancy. However, birth control has been a factor in empowering women around the world, and has greatly contributed to the improvement in sexual health. In developing

BIRTH CONTROL OF SEXTHE SCIENCE I BIRTH countries, avoiding unwanted pregnancies has given women the chance to educate themselves and to ﬁnd work outside the home.

PREGNANCY THROUGH CHOICE Oral contraceptives and other methods of birth control allow people to enjoy sex and to time pregnancy for when it is convenient.

METHODS OF BIRTH CONTROL PELVIC X-RAY Natural methods, such as coitus interruptus, and some barrier A color-enhanced X-ray of a woman’s methods have been used for hundreds of years. Modern methods pelvis shows a ﬁtted intrauterine device started to become widely available in the 1960s. The main types (pink). From this elevated angle, it appears to be ﬁtted upside-down, but currently used are barrier methods, hormonal methods, and this impression is due to the naturally intrauterine devices (IUDs). These all operate either as contraceptives, forward-folded position of the uterus. which prevent fertilization of the egg, or as contragestives, which prevent a fertilized egg from implanting in the uterus.

BARRIER METHODS THE INTRAUTERINE DEVICE (IUD) Sealed ring Devices that form a physical barrier between blocks IUDs have to be ﬁtted by a doctor or nurse the sperm and egg are known as barrier entrance to and can stay in place for several years to methods. The four main types are male and uterus give long-term contraception. There are two female condoms, the cervical cap, and the diaphragm. main forms: those made of copper, and Condoms are usually disposable, while caps and those that contain progesterone. Both diaphragms can be used many times. They all prevent Open ring stimulate the release of prostaglandins from pregnancy by stopping the sperm from entering the the uterus, making it inhospitable to eggs uterus via the cervix. Condoms also prevent sexually and sperm. Progesterone-secreting IUDs transmitted diseases. Barrier methods are popular also thin the uterine lining, increase cervical because they are cheap and easy to use, but are less mucus, and inhibit ovulation. IUDs work reliable than other methods. Over a year, a woman has mainly as contraceptives, but they may also FEMALE CONDOM a 2 in 100 chance of getting pregnant if a condom is MALE CONDOM A thin plastic or rubber pouch prevent implantation (contragestive). used each time she has sex. Caps and diaphragms are Usually made of latex, a male connects two ﬂexible rings; one T-shaped frame even less reliable, but their effectiveness is improved by condom is worn over the penis is placed deep inside the vagina, using a spermicide (a gel that kills sperm). during sex and then discarded. and the other stays outside. Cervix Cap Uterus Diaphragm

Uterus Removal cords Position Can be felt in uterus with fingers IUD fits in uterus, to check that with arms against Vaginal IUD is in place the fallopian tubes wall CAP DIAPHRAGM FITTING AN IUD CERVICAL CAP DIAPHRAGM Uterus size is measured with a small device The small, flexible cap made of rubber is placed The diaphragm is larger than the cap. Its dome-shaped before an IUD can be fitted. Progesterone high up in the vagina. It fits securely over the body is bounded by a flexible ring that sits against the IUDs tend to be large and can be difficult to cervix, blocking the entrance to the uterus. vaginal walls, blocking the entrance to the uterus. insert into women who have not given birth. 68 BIRTH CONTROL

THE ROLE OF ESTROGEN

There are several kinds of estrogen, and all are produced in the ovaries in response to stimulation by the hormones FSH and LH. They are involved in the fertility cycle of all

vertebrates. Estrogen is also an important I THE SCIENCE OF SEX component of the combined oral contraceptive pill, as well as the morning-after pill. Estrogen found in contraceptives is usually synthetic, but some estrogen prescribed to humans is extracted from the urine of pregnant horses.

ESTRADIOL This light micrograph shows estradiol crystals. Estradiol is one of the estrogen hormones that controls the menstrual cycle.

EMERGENCY CONTRACEPTION The morning-after pill is a term for a variety of different drugs that are used to prevent pregnancy after unprotected sex. Some pills contain a progesterone-like hormone, others combine estrogen with progesterone, and pills such as mifepristone block the effects of progesterone. Although different in composition, these drugs all prevent fertilization by two methods: either by delaying ovulation; or by making it difﬁcult for sperm to reach the egg. However, their main HORMONAL METHODS method of action is to delay ovulation, so The most well-known hormonal method Pituitary gland the morning-after pill is much less effective FSH and LH secretion is the combined oral contraceptive pill (the are suppressed. if ovulation has already pill). It contains higher levels of estrogen occurred. Although less and progesterone than are normally found effective, IUDs can also Ovulation in the body. Every month, as natural levels be used for emergency Estrogen, progesterone, of progesterone and estrogen fall, the contraception because or low-dose pituitary gland produces follicle-stimulating they stop a fertilized mifepristone pills stop Oral application the rise in LH—this hormone (FSH) and luteinizing hormone egg from implanting. Taking oral contraceptives prevents the egg from (LH) to trigger ovulation. High levels daily builds up hormone developing and delays of estrogen and progesterone from the levels in blood. ovulation. pill will prevent this sequence of Hormones events. Contraceptive implants also in bloodstream block ovulation, releasing a steady Fertilization stream of hormones from under the Progesterone pills make Contraceptive implants skin. The progesterone-only pill (mini the inside of the uterus An implant can be inserted too alkaline for sperm pill) can prevent ovulation although under the skin—it steadily Effects of emergency to swim and also less successfully than the combined releases a ﬁxed amount of contraceptive thicken cervical mucus. pill; its main function is to thicken hormones into the blood. This prevents the cervical mucus and prevent sperm sperm from reaching and fertilizing the egg. from reaching the fallopian tubes.

Ovaries Low levels of FSH and LH OCCASIONAL USE Implantation prevent ovulation. Emergency IUDs can prevent the USING HORMONES TO contraception is fertilized egg from PREVENT PREGNANCY designed for use when implanting in the uterus Contraceptive hormones can Endometrium other contraception lining. High-dose disrupt the menstrual cycle Lack of pituitary has failed. A range mifepristone prevents in a range of different ways, hormones stop the lining of drugs or IUDs can implantation, but in low enabling them to be tailored thickening in preparation be used after sex to doses has no effect. to individual preferences. for implantation. prevent pregnancy. 69 AT OVULATION, A MATURE FOLLICLE IN THE WOMAN’S OVARY RUPTURES TO RELEASE AN EGG. IF IT MEETS SPERM ON ITS JOURNEY DOWN ONE OF THE FALLOPIAN TUBES TO THE UTERUS, FERTILIZATION MAY OCCUR. THROUGH A MULTITUDE OF COMPLEX PROCESSES, THE FERTILIZED EGG FIRST BECOMES A BALL OF CELLS. OVER TIME IT DEVELOPS INTO AN EMBRYO WITH A BASIC HUMAN SHAPE, THEN A FETUS THAT CAN MOVE AND RESPOND, AND FINALLY INTO A FULLY DEVELOPED BABY, READY FOR LIFE OUTSIDE ITS MOTHER. THROUGHOUT PREGNANCY, THE MOTHER’S BODY UNDERGOES A RANGE OF CHANGES IN ORDER TO SUPPORT AND NOURISH THE GROWING FETUS. CONCEPTION TO BIRTH Eye bud and liver A primitive eye can be seen 12-week ultrasound An ultrasound scan enables External ear and digits By the 12th week, the on this eight-week old fetus. The dark area in the fetus to be measured, which helps estimate tiny outer ear is recognizable at the side of the the abdomen is the developing liver. pregnancy dates and keep track of growth. head, and separate ﬁngers and toes have formed.

TRIMESTER 1 MONTHS 1–3 I WEEKS 1–12

During the ﬁrst trimester the single-celled, fertilized egg embeds in the uterus and is transformed into a tiny, yet recognizably human, embryo with all its major organ systems in place.

The first trimester is a time of remarkable growth and development. This period of initial human development can be fraught with The single-celled, fertilized egg divides rapidly into an embryo, then danger. As its organs are forming, the embryo is especially sensitive a fetus. Although there is much growth and maturation to come, by to harmful influences, including drugs, pollutants, and infections. the end of this trimester the fetus has a recognizably human form, The first trimester is the time when congenital damage is most likely with facial features, sense organs, fingers and toes on the end of tiny and pregnancy loss is most common, but by the end of the trimester limbs, and even tooth buds, fingerprints, and toenails. The brain, the threat is far less. Although the woman may not appear noticeably nervous system, and muscles are all functioning and the fetus can pregnant until the third month, she may notice her waistline perform involuntary reflexes, such as moving about vigorously, expanding and other early symptoms, such as nausea. It is at the swallowing, hiccupping, yawning, and urinating. end of this trimester that many women announce their pregnancy.

TIMELINE

WEEK 1 WEEKS 2–3 WEEK 4 WEEKS 5–6 Menstruation marks the start Follicle stimulating hormone The uterine lining thickens The thickened uterine lining is A pregnancy test may show a positive of pregnancy if conception (FSH) causes an egg to ripen in preparation for possible ready to receive and nourish result even before a period is missed. occurs in the month following inside a follicle. The follicle pregnancy. the blastocyst. Early pregnancy symptoms may include it. Ovarian follicles start to moves to the surface of the On ovulation, basal body A mucus plug forms in the nausea, increased urinary frequency, fatigue, ripen in readiness for ovulation. ovary and ruptures, releasing temperature rises and cervical cervix to protect the uterus and sensitive breasts. the ripe egg. mucus becomes stringy. from infection. MOTHER

WEEK 1 WEEK 2 WEEK 3 WEEK 4 WEEK 5 WEEK 6 MONTH 1 MONTH 2 WEEKS 1–2 WEEK 3 WEEK 4 WEEKS 5–6 When a mature egg is released from an ovary, If conception occurs, The blastocyst implants in the The embryo divides into three layers, and cells it travels down the fallopian tube toward the the fertilized egg starts to uterine lining. It develops a start to specialize. The outer layer forms the uterus. If the woman has sex during this fertile divide as it travels down ﬂuid-ﬁlled core that will neural tube that develops into the brain and time, the sperm will swim up the fallopian tube the fallopian tube. become the yolk sac and will the spinal cord. FETUS to meet the egg, and fertilization may occur. The hormone hCG is separate the embryonic cells A bulge in the middle layer forms the heart, produced to “switch off” from placental cells. which starts to divide into four chambers the menstrual cycle. and to circulate blood around the body.

72 Developing fetus at 12 weeks By the end of the ﬁrst trimester, the fetus is recognizably human and all its major organs have formed.

WEEKS 7–8 WEEKS 9–10 WEEKS 11–12 Metabolism speeds up, the heart and lungs become Breasts and waistline expand, Increased blood circulation The uterus moves upward out Varicose veins or hemorrhoids more efﬁcient, and blood volume expands to meet and clothing may feel tight. may make some women feel of the pelvis; it can now be felt may be troublesome. the increased demands of pregnancy. The growing uterus may press uncomfortably hot. above the pubic bone. The The nipples, areolae, and Weight gain may become noticeable. on the lower spine, causing Hormonal changes increase “bump” may now show. freckles darken. Brown patches Some women develop nausea, a heightened backache. vaginal discharge. Energy increases and urinary may also appear on the face. sense of taste and smell, and food cravings. symptoms lessen.

WEEK 7 WEEK 8 WEEK 9 WEEK 10 WEEK 11 WEEK 12 MONTH 3 WEEK 7 WEEK 8 WEEKS 9–10 WEEKS 11–12

The intestines bulge to The yolk sac starts to disappear, The nose, mouth, and lips are Buds from the bladder The mouth can open Brain cells multiply form a stomach. as the placenta develops. almost fully formed, and the grow upward to join with and close, enabling rapidly as the brain Limb buds develop Limbs lengthen and eyes have moved to the front developing kidneys. swallowing, and has develops two halves, paddle-shaped ends. develop elbows and of the face. Eyelids fuse over The gonads develop into tiny tooth buds. or hemispheres. webbed digits. The the eyes. either testes or ovaries, A heartbeat may The fetus has reﬂexes primitive tail shrinks. and the ovaries begin to be detected. and may move if the produce eggs. abdomen is pressed.

73 MONTH 1 I WEEKS 1–4 Pregnancy is dated from the start of the woman’s last menstrual period. For the ﬁrst two weeks from this time, the body prepares for conception. A fertilized egg then undergoes rapid cell division as it travels to implant in the uterus, where the development of an embryo begins.

WEEK 1 WEEK 2 The uterine lining (endometrium) has built up during the Once menstrual ﬂow has ceased, cyclical hormonal changes, previous month’s cycle to prepare to receive a fertilized egg. controlled by the pituitary gland in the brain, encourage the If conception has not occurred, the thickened lining is shed. endometrium to start to thicken again in preparation for The onset of this menstrual period is recognized as the start a possible pregnancy. At the same time, the ovarian follicles of pregnancy if conception occurs this month. A woman who continue to ripen. Toward the end of this week, one of these is planning to conceive may already be taking folic acid, eating follicles will become fully mature and rupture on the surface healthily, and doing regular exercise so that her body is in the of one ovary. Ovulation is marked by a sharp rise in basal best possible condition to begin a pregnancy. To maximize body temperature (the body's lowest temperature when at the chance of conception, she may also be tracking her basal rest) and thin, stretchy cervical mucus. After ovulation, the body temperature and changes in cervical mucus in order egg is captured by tiny fronds (ﬁmbriae) at the end of the to detect when ovulation occurs. Hormonal changes during fallopian tube and wafted down the tube, ready to meet menstruation prompt several ovarian follicles in each ovary any sperm that may arrive. Sex now, around day 14 of the to start ripening, although usually only one fully develops. cycle, has the best chance of leading to conception.

BODY MONITORING Watching for subtle changes in her body enables a woman to be aware of when ovulation might be imminent.

CERVICAL MUCUS When fertile-type cervical mucus dries, it crystalizes to form the fernlike pattern seen in this light micrograph.

MENSTRUATION The upper endometrial layer, seen in this electron micrograph, is shed during a period. It is regenerated by the lower layer.

OVULATION Around day 14 of the cycle, surges in follicle stimulating hormone and luteinizing hormone cause a bulge to form on the surface of one ovary, which then ruptures to release the mature egg.

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WEEK 3 WEEK 4 Up to 350 million sperm are released in a single ejaculation, The blastocyst arrives in the uterus on average six days after but fewer than 1 in 1,000 manage to pass through the cervix conception—the endometrium is now thickened, ready to into the uterus, and only around 200 reach the correct receive and nourish it. Hormones also thicken cervical mucus fallopian tube to meet the egg. At the moment of conception, so that it forms a plug in the cervix, which protects the uterus a single sperm is drawn into the egg, which then blocks during pregnancy from infections that might otherwise travel entry to others. The fertilized egg produces a hormone up from the vagina. The blastocyst now develops a fluid- called human chorionic gonadotropin (hCG) that “switches filled cavity, creating two layers of cells. The outer layer off” the menstrual cycle by stimulating continued production (trophoblast) burrows into the endometrium and will become of progesterone, the hormone needed to maintain the the placenta. The inner cell mass forms the early embryo endometrium. The egg moves down the fallopian tube and (embryoblast)—these cells then differentiate into a two-layered divides, forming a two-celled zygote and then a cluster of embryonic disk. The fluid-filled cavity develops into a yolk smaller cells called blastomeres. By the time it reaches the sac that will provide nourishment for the embryo during the uterus, it is a ball of around 100 cells called a blastocyst. early weeks, until the placenta has developed.

INTERCOURSE Sexual positions where the penis is high in the vagina help with conception; raised legs after sex may also help.

BALANCED DIET Even if the pregnancy is still unconﬁrmed, it is vital to eat a healthy diet to support and nourish a potential embryo.

CELL DIVISION EARLY DEVELOPMENT Repeated division (cleavage) of The blastocyst in this computer- the initial zygote results in a mass generated image has eroded of embryonic cells, seen in this into maternal tissue and is scanning electron micrograph. embedded in the endometrium.

75 CONCEPTION TO BIRTH

MOTHER AT FOUR WEEKS MONTH 1 I WEEKS 1–4 Normal female anatomy is shown here because it is still MOTHER too early to see any visible MOTHER AND EMBRYO changes in the internal 65 beats per minute arrangement and size of the mother’s major organs. 107/70 At the start of each menstrual cycle, the mother’s body prepares Lungs 71⁄2 pints (4.26 l) for a potential pregnancy. During the first two weeks, there will The lungs here are in their be no outward signs of ovulation or the changes in the uterine normal position. During pregnancy, the diaphragm The hormone hCG is released lining in preparation for pregnancy. After the uterine lining has pushes up and the lungs when the embryo implants. been shed, a rejuvenated lining emerges that thickens over the adapt to their new position. It is detected in the mother’s urine by pregnancy tests. following one or two weeks. Under the influence of progesterone Bowel The transverse colon, below and estrogen, the lining becomes sticky and nutrient-rich in the stomach and above the order to encourage and support successful implantation of the small bowel, is in its normal 20% position. As the pregnancy fertilized blastocyst. In each cycle, the chance of conception is advances, the bowel is Around 20 percent of around 40 percent. The first clue that conception has occurred displaced up as the uterus women become more expands out of the pelvis. sensitive to odors in the first may be a slight implantation bleed, which can be confused with few weeks of pregnancy. a very light period, although a missed period is usually the first Uterus The uterus is approximately definite sign that a woman is pregnant. A pregnancy test taken Once it has been released, the size of a pear and an egg survives for 24 hours around week four will confirm the pregancy. is protected within the bony pelvis. if it is not fertilized.

1234567891011121314151617181920212223242526 27 28 29 30 31 32 33 34 35 36 37 38 39 40 STATISTICS EMBRYO The sex of the embryo is Corona radiata Numerous sperm reach the egg and will attempt determined by the sperm The large egg cell is 2 to enter it as soon as they arrive. When a at the point of conception. surrounded by smaller WEE corona radiata cells. KS single sperm has successfully burrowed If the sperm is carrying a Y through the outer wall of the egg, chromosome, the embryo is Fallopian tube the wall undergoes a change male; an X chromosome will Fertilization occurs in lead to a female embryo. the widest portion of known as depolarization. This prevents any the fallopian tube, The heart starts beating at known as the ampulla. further sperm from three weeks at a relatively penetrating and slow 20–25 beats per minute. fertilizing the egg. By the third month, this has increased to an incredible rate of 157 beats per minute. 1 /16 in By day 28 the embryo grows 1 /16 in (1 mm) a day, but is Fertilization Sperm is about to break smaller than a match head. through the outer wall and fertilize the egg. As a result of cell division, the blastocyst contains 100–150 cells by the time it enters the uterine cavity to implant. The cells are arranged in a three- layered sphere. from occurring. menstruation menstruation Endometrium pregnancy and prevent pregnancy and prevent estrogen, which support the Uterine cavity Uterine hormones progesterone and hormones progesterone and to initiate the release of lining. This sends signals to the ovary implanted and buried within the uterine By the fourth week, the early embryo is completely is completely By the fourth week, early embryo S K E

4 umbilical cord. umbilical Connective stalk Connective Blastocoel eventually form the form eventually Connective tissue will tissue Connective within the blastocyst within the blastocyst This fluid-filled cavity cavity This fluid-filled creates a space for the for a space creates embryo to expand into. to embryo Myometrium Early placenta Early Embryo Yolk sac Yolk outer wall of the wall outer Sperm tail tail portion. THE UTERUS noticeably has not yet The uterus of in size, but as a result increased it is much blood flow enhanced protected remains The uterus softer. until about cavity within the pelvic has when the embryo 12 weeks, in the cavity. the space outgrown Amniotic sac egg by forward forward egg by from the uterine cavity. the uterine from from the section of from Sperm reach the the Sperm reach blastocyst that is farthest is farthest that blastocyst a two-layered disk. a two-layered of cells arranged in in arranged of cells The future placenta forms forms placenta The future Syncytrophoblast propulsion from the from propulsion The embryo consists consists The embryo These specialized cells These specialized cells erode into the maternal the maternal into erode Endometrium tissues and blood vessels. tissues contain multiple nuclei and nuclei multiple contain Perimetrium Midpiece Ovary Fallopian tube Fallopian will reach the egg. will reach to provide energy. energy. provide to Only the fittest sperm Only contains mitochondria mitochondria contains The body of the sperm Uterus Uterus forward. usually tipped usually The main body The main body of the uterus is of the uterus Cervix Sperm head Vagina the nuclei fuse. the nuclei contains genetic genetic contains material from the from material with the mother’s with the mother’s Mucus plug father that will enter will enter that father the egg and combine the egg and combine genetic material when material genetic The head of the sperm The head MONTH 1 I CONCEPTION

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CHANGES IN THE FOLIC ACID UTERUS From conception, the uterus Folic acid is a B vitamin found in some fruit and many has only six days to prepare green vegetables. It reduces the risk of spina bifida to receive the blastocyst. The (defects in the spinal cord and vertebral column) by 75 percent. However, it can be difficult for even the menstrual cycle stops as the healthiest diet to provide adequate folic acid, and ovary secretes estrogen and supplements are recommended for all progesterone from the empty women planning to become pregnant. follicle (corpus luteum) at the site Folic acid should be taken for three of ovulation. The uterine lining months before pregnancy and continued for the first three months (endometrium) becomes thicker, of the pregnancy. more receptive, and “sticky” to encourage implantation. Glandular activity Endometrium Endometrial gland BEST VEGETABLES increases, levels of estrogen and progesterone Regenerates Produces secretions that Broccoli, cabbage, following prepare the endometrium spinach, and brussels rise, and blood supply increases. Not all fertilized menstruation for implantation sprouts all contain eggs implant, and implantation occasionally ENDOMETRIUM folic acid. Steaming The outermost layer of the endometrium is the best method occurs outside the uterus as an ectopic pregnancy. (uterine lining) is shed at the end of each of preparation. The endometrium is only actually receptive to menstrual cycle. The deeper glandular layer implantation for a mere one to two days. is retained for the next menstrual cycle. 78 WEEKS 1–4

MONITORING FERTILITY The timing of ovulation can vary with the length of the menstrual MALE FERTILITY cycle but in the absence of pregnancy it is followed by menstruation 14 days later. For women with very irregular cycles, where the Males remain fertile throughout life from early puberty. Fertility is not strongly linked with the volume of ejaculate, but is based on the overall sperm count, timing of ovulation is difﬁcult to predict, measuring basal body sperm shape, and motility. Laboratory semen analysis is vital for the investigation temperature and assessing the quality of the cervical mucus can of a couple’s fertility problems. Although sperm counts decline with age, this provide clues to the fertility window. Once released, the egg will does not usually signiﬁcantly impair fertility. Abstinence for several days prior survive for only 24 hours if unfertilized. The fertile window is open to intercourse around the time of ovulation will improve conception chances. Several conditions can reduce fertility (see pp.222–23), and fertility can be slightly longer than this because sperm remain active in the fallopian improved with lifestyle changes such as reducing smoking and alcohol intake. tubes for 48 hours, with some remaining active for up to 80 hours.

FERTILE WINDOW

CHANGES WITHIN 28-DAY CYCLE FERTILE WINDOW THE BODY 123456789101112 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

Basal body temperature 98.1 An accurate thermometer can measure the tiny 0.4–0.9° F (0.2–0.5° C) rise in 97.9 basal body temperature that signiﬁes that ovulation has taken place. The 97.7 temperature should be recorded daily, because the sudden increase is crucial. (°F) TEMPERATURE 97.5

Menstral cycle Carefully recording the details of each menstrual cycle will reveal if they are regular. Average cycle length is 28 days, but the normal range is 21–35 days. Irregular cycles are different lengths most months, making it difﬁcult to calculate the time of ovulation. MENSTRUATION PREOVULATORY PHASE OVULATION POST-OVULATORY PHASE

Cervical mucus Under the influence of estrogen, cervical mucus changes at ovulation to facilitate MENSTRUATION DRY WET, STRETCHY DRY (FEW SECRETIONS) the passage of sperm through the cervical canal. The mucus becomes First wet day Wettest day stretchy, thinner, and less acidic in order to promote sperm motility. Later, under the influence of progesterone, these changes are reversed and the passage OVULATION TRIGGER of sperm is restricted by thicker mucus. A sudden surge in luteinizing hormone (LH) triggers ovulation of the dominant follicle, WET DAY TEST which matures under the influence of follicle Stretching cervical stimulating hormone (FSH). About 12–24 hours mucus between the before ovulation, LH levels increase 10-fold, thumb and forefinger causing rupture and release of the egg from will test its quality. If it the dominant ovarian follicle. is thin, watery, slightly stretchy, and forms a string, it is likely that ovulation is taking place. KEY FSH LH

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28-DAY CYCLE FERTILE WINDOW

79 CONCEPTION For conception to take place just one of the millions of sperm released must penetrate the egg. However, the sperm must ﬁrst

I CONCEPTION swim through the cervix and uterus into the fallopian tube, and only a few will successfully reach their goal.

After release from the ovary, the egg is swept into the PASSAGE OF THE EGG DAY 15 Swept up by the ﬁmbriae fallopian tube by the frondlike ﬁmbriae. Fertilization usually at the end of the fallopian tube, the egg takes place in the wider mid-portion of the fallopian tube, passes along the tube to rest within the called the ampulla. Most of the millions of sperm released, wider ampullary portion. Successful fertilization usually occurs at however, do not make the journey this far. This is an this position and can occur important factor because it improves the chance of only up to one or two days after ovulation.

CONCEPTION TO BIRTH BIRTH TO CONCEPTION the ﬁttest sperm reaching and fertilizing the egg. Path of egg

Ampulla Usual site of fertilization 200–300 sperm enter each tube

Ovary

Fimbriae 100,000 sperm enter uterine cavity

60–80 million sperm pass cervix DAYS 12–14 SPERM RACE Millions of 200–300 million sperm sperm are released in the 7 1 enter vagina /100– /5 ﬂ oz (2–6 ml) of ejaculate. Movement is limited, but the cervical mucus and receptive uterine environment lead to forward progression of up to 1 1 /16– /8 in (2–3 mm) per minute.

CAPACITATION OF SPERM

Sperm can move once in the vagina, but their movement is restricted until they reach the more favorable, less acidic environment of the uterus. They are unable to fertilize an egg until they have undergone the process of capacitation. This involves removal of the protein coat over the head of the sperm (acrosome), allowing it to fuse with the egg. Capacitation does not last long and only occurs once to each sperm. Usually only the strongest, most mature sperm will complete capacitation as they journey toward the egg.

Tail Acrosome OVULATION Usually a Nucleus DAY 14 single dominant follicle is matured to the point of ovulation. In a 28-day cycle, ovulation typically occurs on day 14. Ovulation will occur on an earlier day in shorter Neck Head cycles and later in longer cycles. In any given cycle, the chances of successful fertilization are approximately 40 percent. 80 CONCEPTION TO BIRTH Polar Polar bodies 6. FUSION Corona radiata Corona . The female pronucleus pronucleus . The female

FUSION OF GAMETES When the sperm enters Zona pellucida FERTILIZATION FERTILIZATION are sperm Numerous (23 from each pronucleus). each (23 from Male pronucleus Male number of 46 chromosomes number of 46 chromosomes Female pronucleus Female Egg cytoplasm in a single nucleus containing the full containing in a single nucleus The pronuclei meet and fuse, resulting fuse, resulting meet and The pronuclei 16 DAY required to stimulate the corona radiata radiata the corona stimulate to required to the egg in order surrounding layer This allows reaction. start the acrosomal the sperm through a single by penetration the egg. pellucida into Unless inner zona hundred several low, very are sperm counts the egg approximately sperm will reach ejaculation. after 5–20 minutes Double-layered Double-layered egg membrane DAYS 16–17 DAYS pellucida that in the zona a reaction the egg, it precipitates entering sperm from other prevents and as the pronuclei its ﬁnal meiotic division, completes die and they fuse. other their membranes each approach The sperm’s head head The sperm’s becomes the male the male becomes female pronucleus. female pronucleus; the egg pronucleus; nucleus becomes the becomes nucleus 5. PRONUCLEI FORM 5. PRONUCLEI 1. CORONA RADIATA 1. CORONA combined with fast tail with fast combined reach the zona pellucida. the zona reach Enzymes in the acrosome Enzymes in the acrosome movements enable the sperm to the sperm to enable movements and this outer layer through pass Burrowing sperm Burrowing 4. PENETRATION OF EGG 4. PENETRATION head and tail enter the egg, the egg, and tail enter head leaving the cytoplasm behind. the cytoplasm leaving As the sperm’s head pierces the the pierces head As the sperm’s egg membrane, the zona pellucida the zona egg membrane, any other sperm. Only the sperm’s the sperm’s any other sperm. Only The tail propels it forward. The tail propels alters its stucture to block entry to entry to block to its stucture alters Acrosomal enzymes digest a enzymes digest Acrosomal 3. DIGESTING A PATHWAY 3. DIGESTING 2. ACROSOMAL REACTION 2. ACROSOMAL release of acrosomal contents. acrosomal of release pathway that allows the sperm allows that pathway the sperm’s head to trigger the trigger to head the sperm’s On contact, glycoprotein in the glycoprotein On contact, zona pellucida binds to proteins in proteins pellucida binds to zona passage through the zona pellucida. the zona through passage Sperm Ovary release to Ruptures a ripe egg Fimbriae egg Guide released tubes fallopian into Swim along fallopian Swim along fallopian egg reach tube to THROUGH THE FALLOPIAN TUBE This electron micrograph shows a fertilized egg (called a zygote, shown here in green) passing along a fallopian tube, where it divides repeatedly to form a ball-like cluster of cells. After 17–18 days of pregnancy, the cluster of cells (now called a morula) enters the uterus.

Ampulla Thin-walled, almost muscle-free midsection is largest part of fallopian tube, where fertilization often takes place

Fallopian tube

Path of egg CONCEPTION TO BIRTH TO CONCEPTION

Fimbriae

Ovary Ovarian ligament

Blastomeres Cells produced by rapid division of Zona pellucida fertilized egg, each Membrane with its own nucleus prevents further Cilia sperm from Fallopian tube is lined entering with tiny hairs that fertilized egg help transport egg

Two cells Fertilized egg Egg divides into Goblet cell Cell has a single two cells, each Secretes mucus into nucleus with its own fallopian tube nucleus FERTILIZED EGG The zona ZYGOTE Within 24 hours MORULA The DAY 17 pellucida now depolarizes, DAY 18 of fertilization the zygote DAY 20 morula is still preventing further sperm from entering the egg. duplicates the nuclear genetic material then divides contained within the zona pellucida at this The male and female pronuclei combine to produce into two cells by mitosis (see p.50). Through a stage. This is possible because cell division the “zygote,” which prepares for the ﬁrst cell division. sequence of rapid cell divisions, 16–32 cells, called has occurred without cell growth. The morula In rare instances, two sperm simultaneously fertilize blastomeres, are produced. These form the morula, travels the length of the fallopian tube to the egg, resulting in a molar pregnancy (see p.227). which is Latin for “mulberry.” emerge into the uterine cavity for implantation. 84 FERTILIZATION TO IMPLANTATION Before implantation, the fertilized egg divides rapidly, but stays the same size and encased in the protective zona pellucida. In order to implant and grow further, the blastocyst erodes a hole in the zona pellucida so that it can squeeze through and bury itself in the uterine lining.

Not all fertilized eggs will implant successfully. The uterine lining is of the egg is blocked, it may implant in the fallopian tube, stimulated for implantation by progesterone, which is produced by resulting in an ectopic pregnancy (see p.227). The hormone hCG is the ovary responsible for ovulation. This reaction makes the lining triggered by implantation. This leads the corpus luteum to produce sticky and full of nutrients to support the blastocyst. If the passage hormones, that support the pregnancy for the ﬁrst 11–12 weeks.

Uterine cavity

Blastocyst cavity Center of blastocyst develops a ﬂuid-ﬁlled cavity

Cytotrophoblast Layer of cells will become inner layer of placenta Syncytiotrophoblast Outer trophoblast layer breaks away from cell mass and burrows into endometrium, creating a path for cell mass to implant

Nuclei of syncytiotrophoblast

Endometrium Embryoblast Inner mass of cells will develop into embryo Endometrial blood vessels

TWINS

A twin pregnancy arises from one of two mechanisms. Uterine cavity Monozygotic twins occur where

a single fertilized egg divides into two same-sex identical twins (see Enlarging cell mass p.114). Fertilization of two eggs results in dizygotic nonidentical twins of the same or different sex.

Degenerated zona pellucida One fertilized Expanding cell mass breaks egg divides through zona pellicida

MONOZYGOTIC TWINS BLASTOCYST As the morula IMPLANTATION 21 DAYS divides, it transforms into 23 DAYS Progesterone has prepared Two separate a blastocyst, which has an inner compact cell group the uterine lining, making it sticky. Once attached, the eggs are surrounded by outer cells. The inner cell mass outer cells of the blastocyst tunnel into the uterine fertilized (embryoblast) will become the embryo, and the lining. This triggers the release of hCG, which makes outer cells (trophoblast) will be the placenta. As the the corpus luteum in the ovary produce estrogen and DIZYGOTIC TWINS blastocyst expands, it breaks out of the zona pellucida. progesterone to maintain the early pregnancy. 85 Blastocyst cavity Cells from embryoblast spread out to line cavity, which now becomes yolk sac

Yolk sac Amniotic cavity Lined with cells derived from embryoblast, this Amnion sac will provide early Layer of embryonic cells sustenance for embryo that line amniotic cavity Embryonic disk Connective tissue Original cell mass Loose tissue forms Syncytiotrophoblast (embryoblast) from cells of yolk sac has developed into a deﬁned, Endometrial two-layered disk vein

Endometrial capilliary

Embryoblast Endometrium Cells of embryoblast differentiate into two distinct types Cytotrophoblast UTERINE INVASION 25 DAYS The blastocyct continues to invade the uterine wall, facilitated by the outer Lacunae trophoblast (syncytiotrophoblast), which will Isolated cavities form in become the future placenta. The inner cell mass syncytiotrophoblast (embryoblast), which will become the future and fill with maternal embryo, differentiates into two distinct layers. blood and fluid from At implantation the woman may experience a endometrial glands Amniotic cavity slight bleed that occasionally can be confused with a light menstrual period. IMPLANTATION 26 DAYS The blastocyst is completely buried in the uterine wall at this stage, and the implantation point is closed over by a blood clot. By this time, the trophoblast has differentiated into an inner cytotrophoblast layer and a more invasive syncytiotrophoblast layer. The syncytiotrophoblast starts to invade maternal blood vessels. As fluid collects, the amniotic cavity expands.

25 days THE JOURNEY OF A FERTILIZED EGG The fertilized egg takes around seven days, from 26 days the time of conception, to travel down the fallopian tube to the uterus. Along the way, it 29 days grows from a single cell to a cluster of cells called a blastocyst. On reaching the uterus, the blastocyst becomes attached to the sticky uterine wall; it then 30 days buries itself in the endometrium. This not only offers protection but also allows the blastocyst to access nutrients for further cell growth. Once the blastocyst is fully embedded, the only sign of the entry point is a small protective blood clot. EMBRYONIC DEVELOPMENT Successful implantation is vital for the growth of the blastocyst into the early embryo. Once the blastocyst has successfully implanted in the uterus, it undergoes internal reorganization and burrows deep into the uterine lining.

The blastocyst differentiates into two internal cell fetal blood. The cells of the outer cell layer (the DEVELOPING types: the embryoblast, which will form the fetus; syncytiotrophoblast) do not have cell walls, which EMBRYO The implanted and two trophoblast layers, which form the placenta. allows the interconnected cells to spread out and blastocyst develops at The two-layered trophoblast has an inner cell layer aggressively invade and destroy the maternal a very fast rate. By four weeks, the foundations (the cytotrophoblast) that has deﬁned cell walls and tissue. This enables the blastocyst to embed have been laid for the will form the ﬁnal barrier between maternal and deeply in the lining of the uterus. future embryo.

Syncytiotrophoblast Made up of numerous interconnected cells Chorionic cavity Fused cavities eventually form chorionic Cavity cavity (large ﬂuid-ﬁlled space that Spaces form within connective tissue; surrounds amniotic and yolk sacs) these gradually enlarge and fuse, displacing connective tissue

Cytotrophoblast Connecting stalk Each cell in this layer is encased Area of connective tissue within an intact cell membrane remains after chorionic cavity has formed; will form future umbilical cord

Blood networks Networks form as CAVITY FORMATION blood capillaries 29 DAYS Further separation of continue to be the yolk sac from the outer cell wall occurs. The eroded and fuse syncytiotrophoblast layer continues to invade with each other maternal blood vessels, creating networks of nutrient-rich blood. Cavities start to form and fuse within the connective tissue. Amniotic sac

Chorion Yolk sac Comprises both layers of Gradually decreases trophoblast, plus remaining in size as chorionic connective tissue; will form CHORIONIC CAVITY cavity enlarges principal part of placenta 30 DAYS The future embryo is now attached by a connecting stalk. Although smaller than the yolk sac, the amniotic cavity continues to expand—by the eighth week, it encircles the embryo. The yolk sac will nourish the fetus and become the ﬁrst site for production of red blood cells. 87 SAFETY IN PREGNANCY During pregnancy the world can seem like a dangerous place, ﬁlled with potential hazards for the growing fetus. Everything, from infections and medications to animals, domestic chemicals, and even some food, can cause concern. Fortunately, a few sensible precautions can minimize the hazards and help ensure a healthy pregnancy.

INFECTIOUS HAZARDS infections she contracts. In addition CHEMICALS During pregnancy a woman’s immune to affecting the woman’s health, some It is almost impossible to completely avoid system is suppressed to ensure that infectious agents can pass across the chemical exposure, but it is sensible to take her body does not reject the fetus. placenta and may harm the developing simple precautions. Keep the use of chemicals Unfortunately, this means she is more fetus. Particular risks are contaminated to a minimum, use them in well-ventilated susceptible to certain infections, and food, infectious diseases, and diseases areas, wear protective clothing, and follow to developing complications from any carried by animals, especially cats. the safety precautions on the packaging.

IN THE HOME CONCEPTION TO BIRTH I SAFETY IN PREGNANCY BIRTH TO CONCEPTION Although many pregnant women worry about risks from cleaning products, they are in fact relatively risk free. Bleach should not be mixed with other cleaners, however, and cleaning the oven should be avoided if possible. Pesticides and insecticides— even organic ones—have CONGENITAL INFECTIONS CONTACT WITH ANIMALS been liked to birth defects, pregnancy complications, and miscarriage. If possible they should be avoided Infectious diseases, including rubella Some animals, and their feces, carry diseases altogether, especially during the first trimester. Prolonged (German measles), chickenpox, measles, that can harm a developing fetus. Pregnant exposure to paint chemicals may also increase the risk and cytomegalovirus (CMV), can cross the women should stay away from cat litter, of miscarriage and possibly birth defects. While there placenta and cause congenital infections in birdcages, reptiles, rodents, and sheep at is currently no firm evidence that hair dyes harm the the fetus, which may result in various birth lambing time. Cats must be kept away from fetus, it also makes sense to minimize exposure to these defects. Although it is relatively rare, the risk food preparation and eating areas, and hands kinds of chemicals. Highlights or streaks are a better is highest if infection occurs during the first should be washed after touching them. alternative to overall hair treatments, and vegetable- trimester. Vaccinations should be kept up-to Gardening with bare hands should also be based dyes, such as henna, are also a good option. date, and people with infections be avoided. avoided in case cats have soiled the area.

COLDS, FLU, AND VACCINATIONS DRUGS Because the immune system is suppressed during pregnancy, Any prescribed medicine, over-the-counter women are more likely to catch colds and flu, and to treatments, herbal remedies, or recreational succumb to further complications. The risk of infection can drugs taken during pregnancy can reach be reduced by staying away from people with cold or flu the fetus through the placenta. It is not symptoms, avoiding crowds when possible, and washing always possible to avoid medication, hands after touching communal surfaces, such as faucets, but a doctor can advise which ones are telephones, and door handles. Having the annual flu shot safe during pregnancy. Care should be taken protects against complications and also reduces infection with over-the-counter remedies, which can of the newborn during the first six months of life. contain multiple ingredients.

TOXOPLASMOSIS SMOKING This rare infection is caused by a parasite that is Smoking during pregnancy found in animal feces, bird droppings, poorly is bad for both the mother cooked meat or ﬁsh, soil, and contaminated and the fetus. It has been fruit and vegetables. Infection, especially in linked with numerous the second trimester, can cause eye and brain problems, including damage, congenital abnormalities, miscarriage, an increased risk of stillbirth, premature birth, and low birth miscarriage, premature weight. The most common sources of infection birth, low birth weight, are domestic cats and undercooked meat, so crib death, and breathing precautions should be taken with food hygiene. problems in the newborn.

88 SAFETY IN PREGNANCY I CONCEPTION TO BIRTH PHYSICAL HAZARDS likely to occur. It is advisable to be extra safety- During pregnancy, the woman’s body generally conscious at this time, and to take sensible provides a safe cocoon for the fetus. Special care precautions such as wearing supportive, ﬂat should still be taken to avoid physical hazards. shoes, avoiding contact sports and other dangerous Some women may ﬁnd that a combination of an activities, and wearing a seat belt while driving. altered center of gravity and loose ligaments can Medical advice should be sought immediately make injuries, such as sprains and strains, more after a bad fall, accident, or other injury.

TRAVEL Flying ACCIDENTS AND FALLS Most airlines allow Travel poses two main risks— pregnant women Trips and falls are common during infectious diseases and to fly until the end pregnancy. Balance is altered by a accidents. To reduce the risks, of the 35th week. shifting center of gravity, joints and the destination should be Women with ligaments become lax, and many medical conditions researched carefully and a should check women experience dizzy spells. If a fall doctor consulted about malaria with a doctor or bump is followed by bleeding, pain, protection and immunizations. before flying. or reduced fetal movements, prompt The safety of the water supply medical advice should be sought. should be checked and care taken with food hygiene. Pregnant women are at risk of WORKING ENVIRONMENT blood clots in the legs (DVT), Most women continue working during so they should avoid sitting pregnancy with few adjustments, but for too long on long flights. it is an employer’s duty to ensure that there is no exposure to harmful Seat belts substances or excessive physical A seat belt should be worn with the lap strap under the bump and resting demands. Some employers may allow on the hip bones. The diagonal strap pregnant staff to cut back on their should be to the side of the bump. INCORRECT CORRECT hours, take more breaks, reduce the time spent standing, and provide supportive seating for them. DENTAL CARE Good oral hygiene is especially important during pregnancy. Hormonal changes STRESS increase the risk of gum disease, which Stress can cause increased heart rate, has in turn been linked with an increased blood pressure, and stress hormones. chance of premature birth. Most dental There is limited evidence that severe treatments can be given safely during stress, especially early in pregnancy, pregnancy, but it is important that the is linked to premature birth, low dentist knows if a woman is pregnant, birth weight, and even miscarriage or because some procedures and treatments, stillbirth. Relaxation, regular exercise, such as X-rays and certain antibiotics, are a healthy diet, and sufficient sleep best avoided during pregnancy. should be part of a daily routine.

RADIATION OVERHEATING BEDTIME X-rays can damage a developing fetus, so it Raised body temperature during the Pregnant women can find it hard to is important for a woman to tell her doctor first trimester has been linked with find a comfortable sleeping position, or dentist if she thinks she may be pregnant. an increased risk of spinal deformity particularly later in pregnancy when If a chest or abdominal X-ray, CAT scan, in the fetus. Avoid saunas and hot lying on the back should be avoided or radiation test or treatment is needed, the tubs—just 10–20 minutes’ exposure because pressure from the uterus can benefits must be weighed up against the can increase body temperature to squash blood vessels. It can be even hazards. Most scientists believe there is minimal dangerous levels. A hot bath does not more difficult getting out of bed. risk from ultrasound or from electromagnetic pose the same danger because the top This should be done slowly to avoid fields emitted by computers, mobile phones or half of the body is exposed to cooler giddiness, straining abdominal masts, power lines, and airport screening devices. air, and the water gradually cools. muscles, or aggravating back pain.

89 DIET AND EXERCISE Diet and exercise play an important part in overall health during pregnancy. Eating well and exercising regularly will help the fetus grow and develop healthily, and ensure that the mother’s body is in peak condition and ready for the birth.

WEIGHT GAIN Most pregnant women gain 22–29 lb (10–13 kg) Breasts Placenta Maternal fat Increased blood 1/ 1/ 1/ during pregnancy. Gaining more increases the 1 lb (0.5 kg) 1 2 lb (0.7 kg) 5 2 lb (2.5 kg) 3 4 lb (1.5 kg) Uterus Water retention Amniotic ﬂuid Fetus risk of complications, such as preeclampsia and 1 1 1 3 2 /2 lb (1 kg) 5 /2 lb (2.5 kg) 2 lb (1 kg) 6 /2–8 /4 lb (3–4 kg) diabetes, while insufﬁcient weight gain is linked to premature birth and low birth weight. Weight is also an important consideration before becoming pregnant. If there are any concerns, a midwife or physician can advise on a sensible target weight. 0 12345678910111213141516 WEIGHT GAIN (kg) CONCEPTION TO BIRTH I DIET AND EXERCISE BIRTH TO CONCEPTION

LIMIT OR AVOID harm the fetus. Ideally, guidance on FOOD HYGIENE Some foods that can normally be eaten healthy eating during pregnancy should Food poisoning can be hazardous, and some as part of a healthy diet pose a risk be followed from the moment a women forms, such as toxoplasmosis (see p.88), pose during pregnancy, either because they starts trying to get pregnant. If the special risks. Kitchen surfaces should be kept carry a higher than average risk of food pregnancy is unplanned, however, clean and hands washed after using the toilet, poisoning or because they may contain then a healthy eating regime should before preparing food, after handling raw meat speciﬁc organisms or toxins that could begin as soon as it is conﬁrmed. or poultry, and before eating anything.

SOFT CHEESE AND DAIRY PATÉ AND LIVER SHOPPING, STORAGE, Pregnant women are at risk All meat and vegetable paté AND PREPARATION of contracting listeriosis from may contain listeria and “Use by” dates should never be unpasteurized dairy products, should not be eaten. Liver, exceeded. Raw foods should notably soft and blue-veined sausages, and paté contain be kept separate, and any kind cheeses such as Brie, Stilton, high levels of vitamin A of raw meat stored at the and Camembert. It can cause (retinol), which can cause bottom of the refrigerator so it miscarriage, stillbirth, or birth defects. (High-strength does not drip on other food. neonatal death. Hard cheeses multivitamins or cod liver A separate chopping board and cottage cheese are safe oil containing vitamin A must be used for raw meat, and good sources of calcium. should also be avoided.) and salad, fruit, and vegetables should be washed or peeled.

REHEATING FOOD Food that has been warmed and allowed to cool is far more likely to harbor harmful bugs. Reheated food should be heated for at least two minutes until it is steaming hot. It must be piping hot all the way through before it is served, and eaten immediately. Food should never be reheated more than once. For precooked ready meals, it is important to follow cooking instructions.

COOKING FOOD UNDERCOOKED EGGS CAFFEINE AND OILY FISH Undercooked meat, poultry, Raw or partly cooked eggs ALCOHOL Sardines, mackerel, and and fish may contain may harbor salmonella, one High doses of caffeine have other oily fish should be bacteria, viruses, or parasites cause of food poisoning. been linked with low birth eaten as part of a healthy that cause food poisoning Eggs should be cooked until weight and miscarriage, diet. But the oils concentrate and other diseases. Frozen the yolks are solid, not so caffeine consumption pollutants, which can harm food should be thawed, runny, and foods containing should be limited. It remains a fetus; pregnant women cooked at the correct raw eggs, such as homemade uncertain whether there is a should have only two temperature for the right mayonnaise, or partly cooked safe level of alcohol intake, so portions weekly, and avoid time, and heated all the way eggs, should be avoided. it is best avoided completely. shark, marlin, and swordfish. through before being eaten.

90 CONCEPTION TO BIRTH

HEALTHY EATING ACTIVITY AND EXERCISE jolting forces. A fall, jolt, or blow to the Eating healthily before conception and during Unless there are medical- or pregnancy- abdomen can lead to premature labor, pregnancy helps ensure that the body has the related problems, it is generally safe and women who have had a previous necessary stores of nutrients for a healthy for women to continue with most of miscarriage may be advised to avoid pregnancy. Eating the right balance of the main the physical activities they did before energetic sports and activities. If there food groups will also ensure that weight gain becoming pregnant. The exception is any is any doubt, a physician or midwife in pregnancy remains within healthy limits. activity that could involve an injury or should be consulted.

NUTRITION EXERCISE FOR HEALTHY PREGNANCY A healthy, balanced diet includes plenty of unrefined, Exercise has many benefits during pregnancy and in preparing carbohydrate-rich starches (potatoes, wholegrain the body for the birth. It maintains fitness, strengthens bread, and whole grains), at least five portions of fruit muscles, boosts circulation, and helps prevent varicose veins, and vegetables daily, and sufficient meat, fish, or other constipation, and backache. However, strenuous exercise may high-class protein (eggs, nuts, or legumes). Milk be more difficult. Levels of fatigue and breathlessness are a and dairy produce or other sources of calcium are good guide, as are previous levels of fitness—pregnancy is not especially important for the growing fetus. the time to start a demanding regime. Exercise should be stopped at once if pain or dizziness are experienced. Iron-rich foods Protein 1–2 portions 2–3 portions EXERCISING APPROPRIATELY

HIGH RISK PROCEED WITH CAUTION RECOMMEND Fresh fruit Dairy 4–5 portions products Activities involving high impact As pregnancy progresses, some As weight increases and center of RECOMMENDED 2–3 portions DAILY INTAKE or jolting, or reduced oxygen activities may become harder. Be gravity shifts, non-weight-bearing availability, are best avoided, guided by how you feel and stop activities and those with gentle, especially after week 12, as are if you develop any symptoms: rhythmic movements are best: those with a high risk of accidents: • Tennis • Swimming Unreﬁned • Horseback riding • Running • Bicycling Vegetables carbohydrates • Skydiving • Going to the gym • Walking 4–6 portions 4–6 portions • Skiing or skating • Dancing • Yoga (not supine positions) • Diving • Intense aerobics • T’ai chi

SUPPLEMENTS A woman trying to get KEGEL EXERCISES EXERCISES FOR BIRTH pregnant is advised to take 400mcg of folic acid daily, Exercising the pelvic floor helps prevent weakening from Giving birth demands energy from the time she stops the weight of the uterus and strengthens the muscles used for and the fitter you are, the more contraception until the end giving birth. It reduces the risk of postparatum incontinence likely labor will proceed of the first trimester. It can or prolapse. Kegel, or pelvic floor, exercises are simple and smoothly. Any regular exercise help prevent birth defects can be done in any position. The muscles involved can be is helpful—at least half an hour such as spina bifida. Some identified by squeezing as if to stop urinating midflow, without three times a week. Squats can women may be advised to clenching the abdominal or buttock muscles. They should be help strengthen thigh muscles, take a multivitamin, vitamin squeezed for a count of three, relaxed for three, and repeated and sitting cross legged improves D, aspirin, omega-3 oils, 10 times. This should be done three times a day and gradually flexibility in your pelvic joints. or iron in addition. increased to 10s squeezes and 25 repetitions as often as possible.

Pelvic floor muscles Vagina SEX The muscles around HERBS the vagina form a It is usually safe to have sex Most herbs are safe in sling that supports in pregnancy. Positions may cooking, but avoid basil, the pelvic organs have to be adapted to avoid sage, oregano, and (bladder, uterus, the bump, but the fetus will and bowel). rosemary in high doses. be safely cushioned inside the Never use pennyroyal, amniotic fluid and protected because it can cause Pelvic floor from infection by the cervical miscarriage, or feverfew muscles plug. Physicians may advise and aloe. Raspberry leaf against sex if there is a history tea taken in late pregnancy Pelvis of miscarriage, premature birth, can ease and speed labor. Anus bleeding, or other complications.

91 MONTH 2 I WEEKS 5–8 In this period of remarkable growth, the embryo grows from the size of a grain of rice to that of a raspberry, with correspondingly rapid growth of its vital organs. The woman's uterus reaches the size of a grapefruit, her waist thickens, and her breasts enlarge.

WEEK 5 WEEK 6 The two-layered embryonic disk develops into a three-layered The embryo reaches around 3/16 in (4 mm) long, and its body disk. The outer layer (ectoderm) forms the neural tube that curves over into a C-shape. It has a small primitive tail, and will develop into the brain and spinal cord. Skin, hair, nails, limb buds start to sprout from the trunk. Dark spots appear and sweat glands also develop from this layer. The mid-layer on the face as eyes form, and tiny pits either side of the head (mesoderm) develops into many structures, including the heart will eventually become the ears. The heart is the ﬁrst organ to and the skeleton. From the inner layer (endoderm), the thyroid develop, reﬂecting the embryo’s increasing need for sustenance gland, lungs, intestines, and pancreas will form. The early as it grows. It forms from two tubes that fuse then divide into placenta—known as the chorionic villi—starts to develop and separate chambers. It now beats at between 100 and 140 beats form blood vessels, yet nourishment still comes from the yolk per minute, pumping blood around the body, and can be seen sac at this stage. A pregnancy test may now register positive, on an ultrasound scan. The embryo’s central nervous system even before the woman realizes she has missed a period, develops connections to early muscles, and the embryo and she may experience symptoms such as nausea, bloating, may start to move, although the woman will not feel its increased frequency of urination, and breast tingling. movements until much later on in the pregnancy.

PREGNANCY TEST Over-the-counter pregnancy tests detect the hormone hGC, which is produced when the embryo implants.

WEIGHT GAIN Some women may notice they have gained a small amount of weight by week six. This is perfectly normal and healthy.

NEURAL TUBE This computer-generated image from an MRI scan shows the neural tube running down the middle of the embryo.

EMBRYO AT SIX WEEKS This six-week-old embryo is floating in its fluid-filled amniotic sac. Limb buds and an eye are clearly visible.

92 123456789

WEEK 7 WEEK 8 The embryo continues to grow rapidly to around 5/16 in By the end of the second month, the embryo measures about (8 mm) long—about the size of a kidney bean. The limb buds 1/2 in (1.4 cm) long, the size of a raspberry, and all major organs develop paddle-shaped ends from which fingers and toes will have started to form. The primitive tail begins to disappear, and form. The lens and retina begin to develop in the rudimentary limbs lengthen and develop webbed fingers and toes. Unique eyes, and the liver forms and begins producing red blood fingerprints have already formed. As the elbows develop, the cells. Veins become apparent under the fetus’s skin. The arms curve and can move. The brain matures further, and heart yolk sac starts to shrink as the developing chorionic villi valves form so that the primitive circulation flows in the right increasingly supply the embryo with oxygen and nutrients direction. The lungs continue to grow, and airways develop from the maternal bloodstream. The woman’s clothing may that connect them to the back of the throat. The mother’s now start to feel uncomfortably tight around the waist. uterus is now the size of a small grapefruit and may press on Dietary tastes often change, and some women develop the lower spine, sometimes causing backache. Her waistline is aversions to particular foods. In some women, increased now thicker, and her breasts may appear bigger, although she circulating blood volume may give rise to headaches. will still not look noticeably pregnant to others.

CHORIONIC VILLI BRAIN DEVELOPMENT Chorionic villi contain blood The three main sections of the vessels that tap into the mother's brain are now visible as bulges, blood supply to provide and the cranial and sensory nutrients for the embryo. nerves start to develop.

SMELL AND TASTE Many pregnant women develop either an increased sensitivity or aversion to particular smells and tastes.

STEM CELLS This electron micrograph shows fetal hematopoietic stem cells. These give rise to red blood cells or any type of white blood cell.

93 CONCEPTION TO BIRTH

MOTHER AT EIGHT WEEKS MONTH 2 I WEEKS 5–8 Some women may notice no changes during early MOTHER pregnancy, whereas others MOTHER AND EMBRYO may experience quite 66 beats per minute strong reactions to the huge physiological changes. 106/69 At this stage of pregnancy, a large number of mothers notice 1 Stomach 7 ⁄2 pints (4.33 l) a feeling of nausea (often not exclusively in the morning), Nausea is common from increased fatigue, and the need to urinate more frequently. These six weeks, but it usually common early symptoms of pregnancy may not pass until after passes by about 12 weeks. Progesterone may increase 400 mg 12 weeks, and some women experience them for longer. Many acid reflux or heartburn. Pregnant women should of these symptoms are side effects caused by the hormones that continue to take 400 mg Bowel are produced within the ovary to support the development of folic acid a day, up Progesterone relaxes the to week 12. and growth of the early embryo. Over the next two weeks, the smooth muscle of the intestines, which slows the embryo takes on a more recognizably human form. The growth passage of waste products The first part of the body to of the brain is especially rapid, leading to a head size that is half and can lead to constipation. change shape is the breasts. By the second month they the length of the body. The embryo remains curled up and floats Uterus will have become larger and weightlessly within the amniotic sac. By the eighth week all the The uterus has enlarged the nipples will be darker. organ systems have been formed—they are entire, but minute, slightly, but remains well During the pregnancy, they within the pelvis. will increase by an average and their function is very limited. of 2 in (5 cm) and 3 lb (1.4 kg).

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Yolk sac The earliest blood EMBRYO cells and capillaries Villi form in the wall of Simple villi make up the the yolk sac. The embryo has started to take on a more human 144 beats per minute placenta, which is growing 6 appearance. A number of internal organs 1 more rapidly than the WE ⁄16 in ( 1.6 cm) EK can be seen and, externally, the ear, eye, embryo at this stage. S and limb buds are now apparent. 1⁄32 oz (1 g) Umbilical cord Growth is very rapid at this The short stage, with the embryo umbilical cord is doubling in size over the 3 not yet coiled. /8 in Blood vessels are following two weeks. The fetus is growing rapidly clearly visible. at this stage. In just two Eye weeks, between six and eight weeks, it increases Brachial arches in length by 3 /8 in ( 1 cm). Somite These are the precursors of the The somites lower jaw and neck structures. develop into By eight weeks, development the spine, of the heart is ﬁnally vertebral column, Embryo complete, with all four trunk muscles, The embryo is suspended chambers beating. and skin. in the amniotic ﬂuid. During the second month, Heart the embryo is at its most Development of the heart is almost complete; circulation sensitive to the effects is established and the heart of drugs and other toxins. has started beating. Certain drugs taken by the mother at this stage can Upper limb bud result in birth defects The higher limb buds will or even fetal death. eventually develop into arms. Amniotic sac The thin lining of the amniotic sac The face and neck are more recognizable. The eye has not yet fused with the outer 8 WEE is clearly seen, as are the nose and mouth. chorion layer. This KS Lengthening limbs are held close to the occurs at 15 weeks. Lining of uterus body, and the digits are starting to form. Nutrients from the yolk Chorionic villi Villi branch further and sac have been used up, start to form thin-walled and it consequently tertiary villi. diminishes in size.

Head The head is equal in length to the body. The neck is short, and the chin rests on the chest.

Face The face is becoming more distinct; the eye is prominent because it is not yet covered by an eyelid.

Placenta The placenta is larger than the embryo; some nutrient and gas exchange occurs, but full placental circulation is not yet established.

Uterus By eight weeks, the body of the uterus Skin has started to The skin is thin and increase in size. translucent because there is no fat layer beneath the surface. Upper limb Amniotic sac Looking more The amniotic armlike, the sac continues upper limb buds to expand. have developed fused ﬁngers. Myometrium

Endometrium Perimetrium UTERUS AND AMNIOTIC SAC Mucus plug The embryo is still very small and does not yet fill the uterine cavity. The amniotic sac contains only Cervix 1 /4 fl oz (7–8 ml) of fluid compared with 1 fl oz (30 ml) by 10 weeks and Vagina 3 6 /4 fl oz (190 ml) by 16 weeks. MONTH 2 I KEY DEVELOPMENTS

MOTHER

Syncytiotrophoblast Cytotrophoblast PREGNANCY TESTING (outer layer of (inner layer of A pregnancy test responds to human chorionic gonadotropin (hCG), Human chorionic trophoblast) trophoblast) gonadotropin (hCG) a hormone that is produced after conception and is detectable in the enters maternal blood urine within two weeks. It contains alpha and beta protein molecules from trophoblast

CONCEPTION TO BIRTH TO CONCEPTION (subunits)—the beta subunit is unique to hCG, and it is this element that is measured in the pregnancy test. Tests are now so sensitive, they SYNCYTIOTROPHOBLAST 1 As the embryo embeds, the can recognize a pregnancy even a syncytiotrophoblast burrows into few days before menstruation is due. the endometrium, eroding the tissue and exposing blood Positive result capillaries. It secretes hCG, which then diffuses into the maternal Control panel bloodstream. This hormone is measurable in the circulation Negative result from eight days after conception. READING A RESULT Maternal blood In this test, a positive result requires a blue plus sign in one window and a blue line in Endometrium the control panel. Other tests may display Maternal capilliary the results in a different way.

HORMONE CYCLE Following conception, the usual menstrual cycle is THE CERVICAL MUCUS PLUG suppressed. The endometrium, instead of being shed, is maintained by a chain reaction effected by the three Under the inﬂuence of the hormones stimulated main pregnancy hormones, rendering it ripe to receive by fertilization, cervical mucus alters consistency. and nourish the implanting embryo.

At around four weeks it changes from thin KEY HUMAN CHORIONIC mucus into a thick, ﬁrm plug that sits in the GONADOTROPIN (hCG) cervical canal, sealing the entrance to the uterus. ESTROGEN This forms a barrier against any infections PROGESTERONE ascending from the vagina to the uterus.

Mucus plug BARRIER The mucus plug sits securely in the cervix throughout pregnancy. One of the early Vagina signs of labor occurs when it is released as the cervix begins to shorten and open.

CORPUS LUTEUM TOLERATING THE FETUS hCG in maternal blood 2 High levels of hCG in the blood Pregnancy is a delicate balancing act, and most stops corpus luteum stimulate continued growth of from disintegrating the corpus luteum in the ovary— miscarriages occur in the ﬁrst 12 weeks. The mother’s it would otherwise disintegrate. It immune system needs to accept the developing Maternal secretes progesterone and estrogen into the maternal bloodstream. embryo, which would otherwise be detected as blood vessels

foreign and attacked, while maintaining defenses Progesterone against potential infectants. The mechanism that and estrogen released by protects the embryo from maternal immunity is corpus luteum not fully understood, but the role of progesterone is critical. It forms a blocking antibody that mops up any antigen—substances that provoke an immune response—released by the embryo; it also renders white blood cells less able to attack foreign tissue.

FOREIGN TISSUE Some endometrial white blood cells are naturally more Corpus luteum tolerant than those in the general circulation, and this helps protect the developing embryo. 96 WEEKS 5–8

HORMONAL CHANGES EARLY SYMPTOMS OF PREGNANCY One of the key hormones at the start of pregnancy is hCG, which is Many of the early symptoms of pregnancy are actually side effects released as the embryo embeds in the endometrium. This hormone of the surging hormones that are necessary for a successful is responsible for maintaining the corpus luteum in the ovary, which pregnancy. Symptoms vary between individuals in both timing in turn produces relatively small but crucial quantities of estrogen and intensity. Furthermore, no two pregnancies seem to be alike, and progesterone. Although hCG declines after 12 weeks, the graph and a woman may ﬁnd that certain symptoms may be severe below shows that low levels persist, meaning that a pregnancy test in one pregnancy but not the next. remains positive throughout pregnancy. After 12 weeks, the placenta Many of the symptoms will improve takes over production of estrogen and progesterone, secreting both over time and seem to be related to hormones in massive quantities. Progesterone levels are higher until hCG levels, which naturally decline around 28 weeks, after which estrogen levels dominate. after 12 weeks. The most common early pregnancy symptoms are described in the table below.

KEY ALLEVIATING NAUSEA HUMAN CHORIONIC GONADOTROPIN (hCG) Morning sickness is extremely common and can be highly disruptive. Eating regularly can BLOOD LEVELS BLOOD ESTROGEN help alleviate nausea, as can soothing herbal PROGESTERONE teas, in particular mint or ginger teas. OVULATION 0 4 8 12 16 20 24 28 32 36 40 EARLY SYMPTOMS AGE OF EMBRYO/FETUS (WEEKS) PREGNANCY HORMONES Missed period A woman’s period should follow around two weeks after ovulation The above graph shows ﬂuctuations unless fertilization has occurred; this is most likely if sex took place in the three main hormones that act near to ovulation. A pregnancy test at the time of a missed period throughout a 40-week pregnancy. is sensitive enough to detect the presence of an early pregnancy.

Tender and Changes to the breasts begin soon after conception and include enlarged breasts an increase in breast size, sensitivity, and vascular patterns. Under the influence of the early pregnancy hormones, the ductal system is the first area to proliferate, with the glandular tissue increasing much later in pregnancy. Breast soreness experienced within the first trimester tends to ease as the pregnancy progresses.

Fatigue The exact cause of fatigue during the early weeks is unknown. It does not affect all women and usually improves by 12 weeks. Fatigue may be related to early hormonal changes and the body’s gradual acclimatization to the pregnancy.

ENDOMETRIUM Urinary frequency An increase in blood flow to the kidneys and improvements in 3 This is richly supplied with blood their filtering capacity occur early in pregnancy. Urination may vessels that carry the progesterone and occur more often as a result, although excessively high frequency Uterine or pain on urinating may indicate an infection requiring help. cavity estrogen directly to the tissue, ensuring that it continues to thicken. The implanting embryo will receive its first nutrients Nausea and Commonly known as “morning sickness,” nausea and vomiting are directly from this lining. vomiting the classic early symptoms of pregnancy. They can be present at any time of the day or night, and may be exacerbated by certain foods or smells. Usually it takes a mild form, but in rare cases the more severe hyperemesis gravidarum can occur. Functional layer of endometrium is shed Metallic taste Changes to taste sensation, such as a metallic taste in the mouth during menstruation in mouth or the preference for certain foods, may be experienced. These usually settle during the pregnancy or, if not, very soon afterward. Blood vessels Spotting and Spotting may occur at the time of implantation—this coincides bleeding with the time that mensturation is due and can be confused with Basal layer of endometrium is a light period. The cervix also softens during pregnancy, and this not shed and generates a new may lead to some spotting following intercourse. functional layer each month Constipation Progesterone prevents the uterus from contracting before term, but it also slows down the contraction of all smooth muscle. Progesterone and estrogen This causes digestion to be sluggish, leading to constipation. in blood maintain and thicken endometrium 97 MONTH 2 I KEY DEVELOPMENTS

EMBRYO

THE DEVELOPMENT OF PRIMARY GERM LAYERS Head-end of embryo After implantation, the two-layered embryonic disk undergoes a rapid transformation into a Embryonic disk

CONCEPTION TO BIRTH TO CONCEPTION three-layered disk, following the formation of PRIMITIVE STREAK FORMATION a band of cells called the primitive streak, from 1 During the fifth week, a strip of cells which the third cell layer derives. These three known as the primitive streak forms and lengthens along the surface of primary germ layers are the building blocks from the embryonic disk. At its head is the which every body system is derived. The ectoderm primitive node, which moves toward the future head-end of the embryo. forms the upper layer, the endoderm forms the lower layer, and the mesoderm, which is the final Line of cross section layer to appear, is sandwiched between them. Head-tail axis They represent the first simple differentiation Progression of primitive streak establishes head–tail axis of embryo of cells as they follow separate developmental pathways. Many structures are composed of a Primitive node Amniotic sac combination of all three layers, although some Ectoderm Tail-end are entirely formed from a single germ layer. Upper layer of embryonic disk Future mouth of embryo

Primitive streak BODY SYSTEMS AND THEIR PRIMARY GERM LAYERS Cells move between layers ENDODERM MESODERM ECTODERM Mesoderm • Digestive tract • Skin (dermis) • Skin (epidermis) Middle layer of embryonic disk • Respiratory tract • Bone • Hair Endoderm • Urinary tract • Muscle • Nails Lower layer of embryonic disk • Liver • Cartilage • Tooth enamel • Glands, such as thyroid • Connective tissue • Central nervous system PRODUCTION OF MESODERM and pancreas • Heart • Mammary glands 2 As the primitive streak extends, • Reproductive tract • Blood cells and vessels • Sense-organ receptor cells it forms a depression (the primitive groove). Cells from this groove, known as • Lymph cells and vessels • Parts of eyes, ears, and mesoderm, move between existing layers • Kidneys and ureters nasal cavities of endoderm and ectoderm to become CROSS SECTION THROUGH THE PRIMITIVE STREAK the third layer of the embryonic disk.

Embryonic disk Amniotic cavity EMBRYONIC FOLDING Connecting By the end of the fifth week of pregnancy, differentiation Folding stalk into a flat, three-layered disk is complete, and the embryo Head-end Heart then undergoes a complex three-dimensional folding, from head-end to tail-end and from side to side. This creates the shape of the early human embryo. Embryonic folding results in an enclosed primitive gut tube, which extends from the foregut at the head-end of the embryo, through the midgut, which at this stage is linked to the future yolk sac, and then terminates at the tail-end with the hindgut. The connection between the midgut and the yolk sac gradually narrows until the yolk sac enters into the embryo at the site of the umbilical cord. The connecting stalk to the early placenta is what develops into the Tail-end umbilical cord. A small tube (the allantois) develops from FOLDED SIX-WEEK-OLD EMBRYO the hindgut and protudes into the connecting stalk—this 31 DAYS At six weeks, the embryo has a clearly will eventually connect to the bladder. At this early stage 1 Rapid growth at the head- and tail-ends of the disk identifiable shape. The heart and liver can be results in the onset of embryonic folding. The primitive seen through the translucent skin—the heart of development, many species look similar as the most heart, one of the first organs to develop, forms a small is in the center and the liver is to its right. basic body parts are gradually mapped out. bulge that is initially positioned near the head end. 98 WEEKS 5–8

Neural groove Notochord NEURAL TUBE FORMATION An important structure The neural tube will form the central nervous Ectoderm in coordinating neural STEM CELLS tube development system, consisting of the brain and spinal cord. Human stem cells have the potential Its development begins with the appearance of the Mesoderm to develop into any cell type in the notochord, a column of cells that extends along body. This function is usually lost after Endoderm the cells commit to developing along the back of the embryo and solidify. Ectoderm cells a specific pathway, for example, to above the notochord sink to form a depression, FORMATION OF NEURAL GROOVE become a skin cell, nerve cell, or muscle the edges of which fuse and become a tube. This 1 The solid notochord derives from the fiber. Umbilical-cord blood is a rich tube forms centrally then extends outward along mesoderm layer. Ectoderm cells directly source of fetal stem cells; these provide above sink down to form the neural groove. an exact genetic match for an individual the length of the embryo. It finally closes at the and, because they can be cultured into top of the embryo on the 38th day of pregnancy, Neural folds any cell type, offer great potential for and closes at the base of the spine two days later. meet the future treatment of disease. As the embryo folds, the neural tube adopts Early neural a C-shape—it is not uniform in diameter, but tube Site of future develops dilations at the head-end, identifying the spinal cord forebrain, midbrain, and hindbrain as FUSION OF NEURAL FOLDS distinct divisions from 2 As the neural groove deepens, its edges (the neural folds) gradually come together, the spinal cord. forming an early neural tube.

Somite Neural crest Specialized cells Neural tube will migrate to initiate numerous SOMITES structural Mesoderm segments become developments condensed into pairs called somites. These first form in SPECIALIZING CELLS Neural tube the fifth week of pregnancy. This electron micrograph shows embryonic Neural folds Three or four pairs then FORMATION OF NEURAL TUBE stem cells—their ability to specialize makes fuse and appear each day, starting The neural folds meet, fuse, and finally neural tube them a key focus of scientific research. 3 at the head, until there are break away from the overlying ectoderm. is complete 42 pairs by the sixth week. Failure to fuse results in spina bifida.

Foregut Midgut Hindgut Pharyngeal Amniotic ﬂuid arches Tail bud Heart HUMAN TAILS

A human tail is an extremely rare ﬁnding and its origins are not entirely understood. Unlike a true tail, there are no bones within it, and it simply consists of a length of skin, with a variable amount of nerve tissue, extending from the lowest portion of the spinal column. The condition is often associated with a failure of the lower part of the spine to close around the spinal cord.

Soft tail

Future VESTIGIAL REMAINS umbilical Human tails are usually Allantois Yolk sac cord quite short, whereas 38 DAYS 42 DAYS this image shows a particularly long The head rapidly expands as the embryo lengthens, The amniotic cavity now almost fully encircles the 2 3 example of this causing it to curl around the cardiac bulge. Within the embryo. The tail bud will gradually regress as the head rare condition. embryo, neural crest cells are spreading out to form continues to expand, and pharyngeal arches of tissue components of the eyes, skin, nerves, and adrenal glands. start to form in the future neck and lower jaw region. 99

THE GROWING EMBRYO This seven-week-old embryo is ﬂoating in the uterus, surrounded by the amniotic and chorionic membranes. The remains of the yolk sac can be seen above the embryo's head, and the retina of its eye is clearly visible. The large dark area in the embryo's body is the liver. MONTH 2 I KEY DEVELOPMENTS EMBRYO

Primary chorionic villus NOURISHING THE EMBRYO Protrusions form on inner Initially the embryo receives nutrients from the yolk sac layer of trophoblast and eliminates waste products by simple diffusion. This Outer trophoblast layer soon becomes inadequate, and a placental interface between Yolk sac

CONCEPTION TO BIRTH TO CONCEPTION the maternal and fetal circulations is established. The outer trophoblast layer invades the uterine lining, eroding Connecting stalk maternal capillaries and forming lakes of blood in the Amniotic sac rudimentary placenta. The placental tissue sends out Endometrial gland fingerlike projections, or villi, to maximize the surface Chorionic sac area exposed to blood. These become finer and more numerous, and by the third week they contain simple fetal Erosion Maternal blood from capillaries. A week later, the early placenta surrounds the endometrial capillaries fills entire embryo, but the more distant villi disappear as endometrial glands the mature placenta becomes centered on the umbilical PRIMARY CHORIONIC VILLUS 1 By day 26, the invading outer trophoblasts cord. Nutrient exchange is still restricted until a formal form simple fronds as they invade maternal tissues. circulation develops in the 10th week, with the tertiary Maternal blood leaches into endometrial glands. chorionic villi becoming filled with circulating fetal blood. Secondary chorionic villus Protrusions enlarge to form fingerlike projections

Vessel formation Early blood vessels begin to form within connective tissue

Connective tissue Forms a core within secondary chorionic villus

Wall of chorionic sac Formed by the two layers of trophoblast and the connective tissue SECONDARY CHORIONIC VILLUS 2 By day 28, small lakes of maternal blood have formed as the capillary walls dissolve. The maternal barrier to nutrient exchange has been broken down.

THE CHORION The outer wall of the blastocyst is called the chorion. Blood vessels The chorion starts to fuse with the amniotic sac by eight Form a network within the weeks (a process that may last up until 15 weeks). This villi, connecting the stalk forms a double layer of membranes around the fetus. These and embryo membranes rupture during labor when “the waters break.”

Barrier Inner layer of trophoblast FUNCTION OF THE YOLK SAC prevents maternal and fetal blood from mixing The yolk sac is a structure outside the embryo that is involved in the care and maintenance of the immature fetus. In the early days Diffusion of the pregnancy, when the placenta’s ability to transfer nutrients Development of villi creates is limited, the yolk sac plays a key role in the provision of nutrition a larger surface area for by simple diffusion. In this way, and in other ways, it has a similar nutrients and oxygen function to the liver. The first simple capillaries grow within the yolk to diffuse across sac walls and rudimentary, oxygen-carrying blood cells are formed TERTIARY CHORIONIC VILLUS there too. As the placenta begins to function, the yolk sac reduces 3 Further branching refines the structure of the villi to form tertiary villi. These project into the lakes in size and by the end of the pregnancy, it has disappeared. of maternal blood. Fetal capillaries have not grown so nutrient transfer is still inefficient. 102 AMNIOTIC FLUID The amniotic fluid protects the fetus from trauma and provides space for it to grow and move. It Yolk sac aids lung development and helps maintain the fetus at a constant temperature. At first it is similar to the plasma in the fetal circulation, but as the fetus’s kidneys start to produce urine, this passes into the amniotic fluid. By the end of the pregnancy the fluid is more concentrated and similar to urine. Fetal swallowing and fluid absorption within the gut remove amniotic fluid. As pregnancy advances, amniotic fluid volume 3 steadily increases, reaching 1 /4 pints (1 l) by 32 weeks, but 1 can be as much as 3 /2 pints (2 l). By the end of pregnancy, 9 3 /10–1 /4 pints (0.5–1 l) of amniotic fluid is removed by fetal swallowing and replaced by urine every day.

1,000

Umbilical cord

500

CHANGING VOLUME Toward the end of pregnancy, amniotic ﬂuid Amniotic sac AMNIOTIC SAC VOLUME OF AMNIOTIC FLUID (ml) OF AMNIOTIC VOLUME volume decreases as the The amniotic sac completely 0 fetal kidneys produce encloses the embryo. The yolk 1814 22 26 30 34 38 42 smaller volumes of more sac—being a transient structure— TIME (WEEKS) concentrated urine. remains outside the amniotic sac.

BLOOD DEVELOPMENT From day 31, primitive red blood cells arise in the wall of the yolk BLOOD CELLS sac—they are formed in blood islands with simple surrounding capillaries. The earliest primitive red blood cells contain embryonic Blood cell production in the liver starts at 37 days. Some blood hemoglobin, and they have a central nucleus unlike mature red production occurs in the bone blood cells. By day 74, the fetal liver will have taken over blood cell marrow from as early as 10 weeks production from the yolk sac. Unlike the ﬁrst primitive red blood but the liver remains the dominant cells, the cells produced in the fetal liver can differentiate into any FETAL BLOOD CELLS site until after birth. Red blood cell This electron micrograph shows a type of production is high. Each fetal red of the components of fetal blood. By the end of pregnancy blood stem cell. In the fetus it gives rise to red blood cell survives for only 60 cell production also occurs within the bone marrow. blood cells or any type of white blood cell. days—half that in the adult. The embryo needs iron, Blood islands Cavity formation Lumen Blood cells Angioblasts Spaces form within Cavities grow and Lining of vessel folic acid, and vitamin B12 collect in clusters Angioblast blood islands fuse to form lumen lumen forms cells to produce sufﬁcient to form isolated of blood vessel red blood cells. cell masses White blood cell

Red blood cell

BLOOD ISLANDS CAVITY DEVELOPMENT BLOOD VESSEL FORMATION CELL TYPES 1 Blood islands or aggregates arise in 2 The differentiation between 3 The ﬁrst blood cells produced are Fetal red blood cells resemble the the yolk sac and connecting stalk. The capillary wall and early red blood cells almost exclusively primitive red blood adult type but their hemoglobin inner cells form primitive red blood cells begins with the appearance of spaces cells. A simple network of capillaries is binds more avidly to oxygen. while the outer cells make capillary walls. inside the blood islands. complete by the end of the third week. 103 MONTH 2 I KEY DEVELOPMENTS

EMBRYO

ORGANOGENESIS THE DEVELOPMENT OF THE LUNGS Organogenesis is a process of rapid embryonic development, at Lung development begins at day 50 and continues into early infancy. the end of which all the major organs and external structures have The rudimentary windpipe develops two branches that subdivide appeared. It lasts from the sixth to the 10th week. Different systems into successively ﬁner tubes. The initial branching pattern is common

CONCEPTION TO BIRTH TO CONCEPTION develop concurrently. The respiratory system emerges from an to all embryos, but the final arrangement is unique. By the 18th out-pocketing of the foregut to form the lungs, and the digestive week, 14 divisions have taken place to form the respiratory tree but system gives rise to the intestines, liver, gall bladder, and pancreas. the bronchioles are too large and their walls are too thick for gas The first fully functioning system is the cardiovascular system, exchange (respiration). Recognizable primitive alveoli, with walls thin which consists of the heart and a simple circulation that is enough for gas transfer (see pp.152–53), do not appear until 38 weeks. continuously remodeled as the embryo develops. Pharynx Pharynx Ear Marked by a shallow pit, this is the eventual site of the ear. Trachea Bronchial Brain Respiratory diverticulum buds The rapid development that has occurred in the brain has caused the head to bend over. Tracheal bud Eye The precursor to the lens is Esophagus Esophagus visible; the eyelid has still to develop and close the eye. TRACHEAL BUD BRONCHIAL BUDS Pharyngeal arches These five distinctive ridges 1 The first sign of the developing windpipe 2 On day 56, after the trachea has give rise to many head and or trachea is a pouch that grows outward lengthened sufficiently, it divides into neck features in the fetus. and downward from the esophagus. two bronchial buds; each will form a lung.

Heart Trachea The dark area clearly shows the position of the heart. Right primary bronchus Right Tail tertiary Left This is not a tail in the true Right bronchi tertiary sense, but an extension of the secondary Left primary bronchi skin that covers the spinal cord. bronchi bronchus Limb bud Signs of a developing leg are Left evident although it bears little secondary resemblance to the real thing. bronchi Somites EARLY BODY STRUCTURES Bordering the neural tube, This seven-week-old embryo is about SECONDARY BRONCHI TERTIARY BRONCHI somites differentiate into midway through organogenesis. 3 The bronchial buds branch in a very 4 By day 70, the third series of divisions is skin, muscle, and vertebrae. The development of body systems speciﬁc manner. The right bud branches underway. The result is 10 lung segments on overshadows growth of the embryo. three times and the left branches twice. the right and eight segments on the left.

Liver THE DIGESTIVE SYSTEM Stomach Stomach The digestive system starts as a simple tube joining mouth to anus. Gradually, portions specialize, with Bile duct the stomach first to form, during the seventh week. Liver Dorsal During the ninth week, the bowel lengthens so pancreatic bud much that it cannot be contained within the abdomen and it pushes out into the umbilical cord. Here it Gall bladder Fused Gall pancreatic buds rotates 90° counterclockwise before returning to the bladder Bile duct abdominal cavity by the end of the 12th week. The Ventral Duodenal Duodenal small and large bowel reach their final positions by pancreatic bud loop loop the 14th week. By 17 weeks, amniotic fluid enters the EMBRYO AT NINE WEEKS EMBRYO AT 10 WEEKS gut as the fetus makes regular swallowing motions. 1 The gut develops specialized structures 2 The two separate pancreatic buds have that branch off the main tube. The early fused, and the bile duct connecting the gall Although the gut cannot move until mid-pregnancy, pancreas is made up of two separate buds. bladder to the duodenum has lengthened. villi in the intestines enable absorption of the fluid. 104 WEEKS 5–8

THE DEVELOPMENT OF THE HEART Endocardial The heart develops early, allowing nutrients to be Fusion of tubes distributed to support the embryo’s development. endocardial tubes into primitive It is the first system to work fully. The heart beats heart tube from day 50, and blood starts to circulate two to Direction of blood flow three days later. A cardiac bulge appears above the insertion point of the umbilical cord, and the heart is formed here from two thin-walled tubes as they fuse from top to bottom. The embryonic circulation continues as the final structure of the heart ENDOCARDIAL TUBES PRIMITIVE HEART TUBE emerges. Looping and remodeling progress rapidly 1 Early on in development, two separate 2 The endocardial tubes merge from the and are completed at the end of the 10th week. and parallel tubes direct blood toward base upward, eventually forming a single the head of the embryo. primitive heart tube by day 50. The fetal heart is lined with a special tissue called endocardium, and the muscular tissue of the heart (myocardium) is unique in its ability to contract Truncus Truncus spontaneously with a regular intrinsic rhythm. arteriosus arteriosus

Bulbs cordis Bulbs cordis DIVISION OF HEART CHAMBERS

The heart has left and right upper chambers (atria) that Ventricle collect blood from the network of veins, and two lower Ventricle chambers (ventricles) that pass blood out of the heart. Atrium The atria and ventricles are divided by walls (septa) that Atrium grow in toward the central crux of the heart (endocardial Sinus cushion). A one-way valve controls blood ﬂow from each venosus Sinus venosus atrium to its corresponding ventricle. The ventricles are separated but the atria communicate via the foramen ovale, which allows oxygenated blood to pass through.

Septum spurium Left atrium SEPARATE REGIONS BENDING OF HEART TUBE 3 Subtle constrictions demarcate separate 4 On day 51, the beating heart tube Foramen ovale portions while cardiac jelly and myocardium elongates and loops to the right, forming Left ventricle (beating cardiac muscle) surround the tube. a spiral. A basic circulation is established. Septum inferius

SEPTUM FORMATION Aorta The septum between the Truncus ventricles is muscular in all arteriosus Superior but its thin upper portion, vena cava which does not contract Bulbs cordis like the musular part. Deoxygenated blood ﬂow

Blood ﬂow Pulmonary trunk Foramen ovale Atrium Tricuspid valve Flow of Mitral valve oxygenated blood

BLOOD FLOW Ventricle From the right atrium, blood passes through the Inferior tricuspid valve or through vena cava the foramen ovale. The S-FORMATION FINAL POSITION OF CHAMBERS left atrium passes blood By day 53, the heart tube has looped The four chambers have achieved into the left ventricle. 5 6 to form an S-shape, bringing the four complete separation by day 84, and chambers to their correct spatial orientation. the heart valves are in place by day 91. 105 MONTH 3 I WEEKS 9–12 This month the embryo becomes a fetus. It is now recognizably human and moves vigorously. By the end of the ﬁrst trimester the pregnancy is well established, and the risk of miscarriage much lower—many women choose this time to announce their pregnancy to the world.

WEEK 9 WEEK 10 The embryo now measures around 3⁄4 in (1.8 cm), about the The embryo ofﬁcially becomes a fetus in the eigth week of size of a large grape, and its tail has disappeared. Fingers start development post-fertilization (the 10th week of pregnancy). to separate, and the wrists bend and move. The nose takes It is now around 11⁄4 in (3 cm) long, about the size of a prune, shape, mouth and lips are almost fully formed, and the eyelids and able to move vigorously. The head is almost half its fuse over the eyes, which will not open again until around the length, with recognizable facial features and ears. Cartilage in 26th week of pregnancy. The diaphragm, a muscular sheet the skeleton begins to harden into bone (ossify), and toenails that will eventually separate the chest and abdominal cavities, appear. Hormones prompt the primitive gonads to develop starts to form, and the bladder and urethra separate from the into ovaries or testes, and the ovaries start producing eggs. lower end of the intestinal tract. The placenta supplies most The external genitals start to differentiate too, but it is not yet of the embryo’s nourishment, and the yolk sac shrinks further. possible to tell male from female. Buds from the bladder grow The woman may notice more weight gain; this is mainly due upward to join with tissue in the pelvis that will eventually to ﬂuid retention and increased blood volume. Her breasts become the kidneys. The woman’s respiratory system begins will probably be noticeably larger and may feel tender. to adapt to meet the demands of pregnancy.

BONE GROWTH At around 10 weeks, fetal cartilage starts to harden and ossify into bone, aided by cells brought in by the blood supply.

FIRST APPOINTMENT Some women may have their ﬁrst prenatal appointment around nine weeks. It can be with a physician or a midwife.

HANDS AND FACE LUNG ADAPTATION At nine weeks the embryo's The mother's lungs adapt to face has started to develop. take in more air. This is to meet The ﬁngers begin to separate the increased demand for and the wrists bend and move. oxygen that pregnancy brings.

106 123456789

WEEK 11 WEEK 12

The fetus is now around 2 in (5 cm) long, about the size of The fetus is now on average 21⁄4 in (6 cm) long, about the a plum. It can open and close its mouth, enabling yawning size of a kiwi fruit. As brain cells multiply rapidly, the brain and swallowing. Tiny teeth buds are forming within the jaw, develops into two distinct halves (left and right hemispheres)— fingers and toes start to lose their webbing, and the skin each one controls the opposite side of the body. Developed thickens and loses its previous transparency. The heart is reflexes mean the fetus may move in response to pressure on beating faster, between 120 and 160 beats per minute, and the abdomen, suck a thumb or fist, and urinate. It begins to blood is circulating rapidly around the fetal body. The woman’s produce its own hormones, and the genitals may show the abdomen may protrude a little, and she may feel increasingly first outward signs of gender. Some women now appear breathless on exertion due to the increased workload of the pregnant and may have to adjust clothing to accommodate heart and lungs. The enlarging uterus now moves upward out the bump. Hormonal changes can cause nipples and areolae of the pelvis, reducing pressure on the bladder, so urinary to darken, although this will be more pronounced later on. symptoms lessen, but existing varicose veins or hemorrhoids Often any nausea now passes, appetite improves, and early may swell up, or new ones may develop. pregnancy tiredness gives way to increased energy.

WELL-DEVELOPED FACE This 3D ultrasound image of an 11-week-old fetus shows its relatively large head and well-developed face.

FIRST SCAN Most women have their ﬁrst ultrasound scan at around 12 weeks. The scan is a useful way to date the pregnancy.

STARTING TO SHOW Some women may notice their clothes becoming tighter as their abdomen starts to enlarge and protrude.

SINGLE OR MULTIPLE The ﬁrst scan will conﬁrm if the pregnancy is single or multiple. A single fetus can be clearly seen in this ultrasound image.

107 CONCEPTION TO BIRTH

MOTHER AT 12 WEEKS MONTH 3 I WEEKS 9–12 Anticipating future demands, the mother breathes more MOTHER deeply, absorbs nutrients MOTHER AND FETUS more efficiently, and her 66 beats per minute circulation system delivers more blood to the placenta. 105/68 Early pregnancy symptoms, such as fatigue and nausea, usually 71⁄2 pints (4.4 l) peak this month, possibly due to high levels of the hormone hCG. Stomach At 12 weeks, hCG levels have During this month, the embryonic period ends and the fetal stage reached their peak, which begins. The yolk sac shrinks, and its role diminishes as the can lead to nausea and sickness in many women. 1 fl oz placenta takes over. The placenta is now far larger than the The volume of amniotic fluid fetus and can easily meet oxygen and nutrient demands and Bowel in the 12th week of pregnancy remove waste products and carbon dioxide. During this month, Rising progesterone levels is around 1 fl oz (27 ml). It will can slow bowel transit times, reach a peak of around energy is directed toward completion of the basic organ structures. leading to constipation. 33 1 /4 fl oz (946 ml) by week 34. A high-fiber diet and The face becomes more recognizable as the eyes form and the drinking plenty of water jaw and neck lengthen, bringing the ears toward their final can reduce symptoms. High levels of progesterone may lead to some women positions. The neck is still relatively short, and the fetus adopts Uterus developing spots or acne. a curled position, with its head held close to its chest. Reflecting The uterus has started to rapid brain growth, the head occupies half the total crown-to- expand and now tips slightly The discomfort of early forward. It can just be felt pregnancy often peaks, then rump length, and in just three weeks the fetus doubles in length. above the brim of the pelvis. improves, in month three.

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Chorionic villi FETUS Well-formed tertiary villi start to appear within the placenta to aid At 10 weeks, placental efficiency improves to support 175 beats per minute nutrient transfer. 10 W the demands of the rapidly growing fetus. 21⁄4 in (5.4 cm) Umbilical cord EEK The fetus’s bowel pushes through into Fetal movements S the base of the umbilical cord. 1 2 encourage the ⁄ oz (14 g) umbilical It reenters the abdomen by cord to coil. 11-12 weeks, rotating as it The embryonic period moves back (see p.122). is complete by week 10, when the embryo becomes a fetus. The fetal period begins with early signs of organ growth. Head The head represents 50 percent of the total fetal length. This is The pregnancy can be a reflection of the amount of accurately dated around brain development that needs week 12 by an ultrasound to occur before other organs measurement of the length and body systems can mature. of the fetus, called the crown-rump length. Ear The ear is quite low on Ultrasound scanning will the jaw line, but over the next two to three weeks it show the fetal heart beat will ascend to its final position. and the limbs. Simple trunk Legs and limb movements can These are less Neck also be seen at this stage. developed The neck is still shortened, Swallowing starts and fluid than the arms; which forces the head toward can be seen in the stomach toes are not the chest and gives the fetus and bladder. fully separated. a curled-up appearance. Ear The shape of ear the external a fully resembles but ear, formed is still the position down. low slightly the amniotic fluid. of dilute urine into of dilute urine into passing minute volumes passing minute volumes begin to function by Eye and large are The eyes wide apart. The spaced developed have eyelids fused; they now and are until closed will remain 26 weeks. around start swallowing. The kidneys start swallowing. The kidneys change is that the fetus can now away from the chest—one effect of this from the chest—one effect of this away neck lengthens, and the head lifts up and neck lengthens, and the head lifts up Head growth starts to slow down at 12 weeks. The Head growth starts to slow down at 12 weeks. The S Jaw buds are Teeth within the forming gum, as the jaw lengthen. begins to K E E

1 Arm limb movements. limb movements. to allow very simple simple very allow to now developed enough developed now The elbow and wrist are and wrist are The elbow Sex fetus is more is more fetus by ultrasound. ultrasound. by The sex of the but it is still too but it is still too early to identify to early weeks than at 10, than at weeks recognizable at 12 at recognizable Placenta UTERUS large is too the uterus 12 weeks By and within the pelvis lie entirely to fit. to in order must flex forward adopt to has enough room The fetus and the amniotic fluid any position, a near-weightless it offers surrounding in. move it to for environment Amniotic fluid At this stage the fluid comes the fluid comes At this stage the across liquids passed from and membranes, placenta, skin, which is not the fetal waterproof. yet lobes, each of which lobes, each arteries. After 12 weeks 12 weeks After arteries. placenta contains 15–20 contains placenta The maternal side of the The maternal these lobes stop forming. these lobes stop contains several branched branched several contains Uterus in the pelvis. in the pelvis. The enlarging The enlarging forward to fit fit to forward uterus now tilts now uterus Endometrium Cervix Vagina Perimetrium Myometrium

Mucus plug MONTH 3 I KEY DEVELOPMENTS

MOTHER

EARLY PRENATAL CARE ADAPTATION OF LUNGS At the ﬁrst meeting, the health care professional offers information The lungs adapt rapidly early on in pregnancy, in anticipation of about pregnancy, healthcare services, and lifestyle choices, including increased oxygen demands. At ﬁrst, this may make the mother feel screening tests and dietary information. The right to decline tests is short of breath, but the changes actually make the lungs work more

CONCEPTION TO BIRTH TO CONCEPTION also explained. This is the stage when questions should be asked efﬁciently. Deeper breathing increases oxygen absorption and and individual care plans discussed. Whether the prenatal care is removes more carbon dioxide. This is achieved through changes hospital or community based, it will include regular meetings with a to the rib position and the elevation of the diaphragm, not through health care professional. Details of the changes to the structure of the lungs. As the diaphragm is pushed hospital and care team involved are up, the residual volume, which is not involved in gas exchange, is noted in the mother’s medical records. decreased in favor of the tidal volume, which is the amount of air that can be breathed in with a normal breath. MEETING THE HEALTH CARE PROFESSIONAL The ﬁrst meeting with a health care professional should be well before 12 weeks, so there is plenty of time to discuss future pregnancy needs. Total lung Vital capacity capacity 4,200ml 3,200ml PRENATAL APPOINTMENTS (1ST AND 2ND TRIMESTERS) Tidal At each prenatal appointment, a number of routine checks and tests are volume performed, to make sure everything is proceeding as it should and to 450ml identify whether additional care or medical attention is required.

TIMING NATURE OF APPOINTMENT Residual 11–14 weeks The ﬁrst ultrasound is carried out, which dates the pregnancy. Many volume hospitals offer the option to screen for Down syndrome at this stage. 1,000ml

16 weeks The blood tests taken at the ﬁrst visit are reviewed. Blood pressure is Normal measured, and urine is checked for protein, which may indicate infection. diaphragm position 18-20 weeks An ultrasound scan is done to assess placental and fetal development. If the placenta is lying low (see p.139) a further scan at 32 weeks is arranged. LUNGS OUTSIDE PREGNANCY The amount of air breathed in with a normal breath 20 weeks Often you will be offered a review with the medical team to ﬁnalize the is the tidal volume. The amount of air breathed out, plan for your pregnancy or to discuss ultrasound results. after a deep breath in, is the vital capacity.

24 weeks If it is a ﬁrst pregnancy, this appointment is for routine checks, including blood pressure, and to measure growth of the uterus.

Total lung Vital capacity capacity COMMON CONCERNS DURING PREGNANCY 4,100ml 3,200ml Some women may be concerned about not feeling the baby move, Lung expands as Tidal but this can vary greatly (see p.138). Nausea and sickness are thoracic volume cavity 650ml normal and may occur up to 20 weeks; heartburn can continue for increases longer. Some discomfort as the uterus enlarges and the ligaments Original position and joints loosen is common, but the of lungs health care professional should be told if it is very painful. Vaginal discharge is Residual volume normal, but it should not itch, smell, or 800ml be accompanied by any bleeding. The need to urinate may also become more Elevated diaphragm frequent, but it should not hurt to do so.

UTERINE PAIN LUNGS DURING PREGNANCY Occasional discomfort is common at this When the diaphragm becomes elevated, the tidal early stage, but constant pain, bleeding, or volume is increased at the expense of the residual ﬂuid loss should always be investigated. volume. This means the lungs can take in more air. 110 9–12 WEEKS

PASSING ON IMMUNITY PROTECTED FETUS IgG antibodies provide the fetus with early Protection for the fetus, and for the baby once it immunity against disease, until it is able to is born, relies on immunity that is passed from boost this with its own antibodies. These are not usually produced until 20 weeks. the mother across the placenta. During pregnancy, Umbilical cord acts as a most viral infections are fought by the mother’s conduit for antibodies immune system. After birth, the antibody between mother and fetus. IgGs enter fetus via the immunoglobulin type G (IgG), which crosses over umbilical artery the placenta from the mother during pregnancy, provides immunity for the baby. Breastfeeding allows immunoglobulin type A (IgA) to pass to the baby for additional protection. However, Maternal blood containing antibodies collects in not all antibodies can pass over to the fetus. intervillious space Immunoglobulin type M (IgM) antibodies, which are produced at the early stages of a viral attack, IgM are too large to cross the placenta. antibody

Maternal artery

Maternal vein Lining of uterus

IgG antibody

Maternal blood ﬂow

IgGs diffuse across placenta wall Umbilical artery PENETRATING THE PLACENTA IMMUNOGLOBULIN G (IgG) Small IgG antibodies can cross the Fetal blood This color-enhanced electron micrograph shows the placental barrier, but larger IgM antibodies flow Y-shaped structure of IgG antibodies. They are the most cannot. This has some benefit, as IgM Umbilical abundant antibodies and are present in all body fluids. antibodies would attack the fetus if its blood IgMs are too large to enter vein They are also the only ones able to cross the placenta. type was different to that of its mother. fetal bloodstream

Air passage NASAL CONGESTION constricted by Nasal congestion (pregnancy rhinitis) is now inflamed conchae a recognized symptom during pregnancy, although it is still not clear why it occurs. It affects one in five women and, although it is often confused with hay fever, it is not an allergic reaction. Nasal congestion can develop at any time during pregnancy, but it Inhaled air settles down 1-2 weeks after delivery. Although no universally successful treatment exists, simple Shelflike, bone conchae divide measures, such as raising the head of the bed, nasal cavity physical exercise, and saline washes, can help. NASAL CAPILLARIES CONSTRICTED AIR PASSAGE A physician will be able to distinguish pregnancy The lining of the nose has numerous capillaries Excess mucus production and irritation to the that warm incoming air. Irritation of the lining lining of the nasal passages both contribute to rhinitis from a sinus infection, which may can lead to engorgement of the capillaries, restricted airflow. To improve airflow, saline require antibiotic treatment. which can exacerbate pregnancy rhinitis. washes may be necessary. 111 BLOOD FLOW IN THE BRAIN This color-enhanced Doppler ultrasound scan shows blood flow in the vessels in the brain of a 12-week-old fetus. The different colors (white, red, and purple) represent blood flow in different directions, and this scan reveals that blood flow is normal in this fetus's brain.

MONTH 3 I KEY DEVELOPMENTS FETUS

THE DEVELOPING PLACENTA UMBILICAL CORD The umbilical cord enables fetal blood to circulate to the The architecture of the placenta continues to mature as placenta (along two coiled arteries) before returning with the surface area expands and the barrier between the nutrients and oxygen to the fetus (within a single wide vein). maternal and fetal circulations thins. The walls of the Normally, arteries—and not veins—are the vessels that carry oxygen. However, veins take blood toward the heart and

CONCEPTION TO BIRTH TO CONCEPTION mother’s arteries have been invaded by fetal cells that arteries away from it, hence the naming of the umbilical vessels. weaken their structure, causing them to dilate, lowering Stimulated by fetal movements, the cord gradually becomes resistance and releasing a continuous stream of blood into coiled. This is a protective the intervillous space. On the fetal side, the villi branch FETAL LIFELINE mechanism that, along with into tertiary villi that float within pools of maternal This photograph, taken inside its jellylike covering (known the uterus, shows blood vessels as Wharton’s jelly), prevents blood. During the ninth week, these villi lengthen, within a section of coiled cord. the cord from kinking. reaching their maximum length by the 16th week. To meet the ever-increasing demands of the growing fetus, however, placental development continues well into the second half of pregnancy. To TWINS improve nutrient and gas transfer further, the villi walls start to thin out, Villous chorion Nonidentical twins (dizygotic) arise from two separate and delicate side branches Frondlike texture of eggs so they may be of the same or different sex. This appear after 24 weeks. chorion provides type accounts for 92 percent of all twins. More rarely, a large surface area for single fertilized egg will divide into two identical, same-sex gas exchange individuals (monozygotic). The timing of this division determines whether there will be one or two placentas Smooth chorion Uterine Oxygen and Maternal Fronds erode as cavity (chorionicity) and one or two amniotic sacs (amnionicity). Maternal nutrients diffuse blood pools sac protrudes into Separate blood into fetal in intervillous uterine cavity Mucus plug vessel bloodstream space CLEAVAGE AFTER 1–3 DAYS amniotic sacs If a single egg divides this early VITAL NOURISHMENT into two identical twins, each will Throughout pregnancy the fetus is exist separately from the other. entirely dependent on the umbilical Because they do not share the cord for incoming nutrients and oxygen same placenta, they do not share as well as for the removal of waste a circulation. There is also no risk products and carbon dioxide. of them becoming entangled. Separate Fetal waste passes back into Separate placentas maternal bloodstream CLEAVAGE AFTER 4–8 DAYS amniotic sacs The twins are in separate sacs Umbilical vein Umbilical arteries (diamniotic) so cannot become carries carry deoxygenated entwined but their circulations oxygenated blood can mix across the joint placenta blood (monochorionic). If one donates Blood flow more blood than it receives, to fetus problems can arise (see below). Shared Shared placenta CLEAVAGE AFTER 8–13 DAYS amniotic sac The thin amniotic membrane separating the twins is absent (monoamniotic) and they share a placenta (monochorionic). Twins that share a placenta may have an unequal share of the circulation: twin–twin transfusion syndrome. Shared Blood flow from fetus Shared placenta CLEAVAGE AFTER 13–15 DAYS amniotic sac GAS EXCHANGE Cleavage after 13–15 days Exchange between maternal and fetal blood produces conjoined twins. occurs in the intervillous spaces. The villi, They may be joined at the head, which are part of the fetus, project into chest, or abdomen. The complex these spaces, where maternal blood circulation and sharing of organs circulates. Gases pass from the maternal at each level carries serious Shared blood into the blood circulating in the villi, implications for separation. placenta while waste travels in the opposite direction. WEEKS 9–12

THE FIRST ULTRASOUND SCAN NUCHAL TRANSLUCENCY SCAN The initial ultrasound scan is usually performed between 11 and A nuchal translucency measurement is offered from the 11th week to 13 weeks 14 weeks of pregnancy. This is the best time to most accurately date and 6 days. It can identify pregnancies the pregnancy and determine the expected delivery date. Dating is at increased risk of Down syndrome. achieved by measuring the fetus from the top to tail, also called the Fetuses with Down syndrome may crown-rump length. This measurement is identical in all fetuses of have an increase in the amount of fluid in the nuchal region, and this, along 11–14 weeks; major differences in fetal size only become apparent with the mother’s age, will generate a in the second half of pregnancy. In this first sighting of the fetus, risk estimate for Down syndrome. The both hands and feet can be seen, fluid in the stomach and bladder scan identifies approximately 7 out observed, and the heart beat recognized. If more than one fetus is of 10 fetuses with Down syndrone. EXCESS NUCHAL FLUID Recently, blood hormone levels have This fetus, photographed within the uterus, present, the number of amniotic sacs and the number of placentas been included to generate a more has excess nuchal fluid, which can be seen can be determined most accurately at this stage. at the extreme left. All fetuses have some accurate estimate. A high risk result nuchal fluid, but the amount may be greater from the integrated screening test than normal for no apparent reason or in Skull Cerebral Nasal will identify 9 out of 10 fetuses association with certain genetic conditions Crown bone hemispheres bone with Down syndrome. and some structural problems.

Umbilical NORMAL SCAN cord With the fetus in proﬁle and clear of the amniotic membrane below, the widest part of the nuchal translucency (space between white plus signs) is carefully measured.

Normal nuchal fold As seen here, the normal, narrow nuchal Heart translucency is most commonly between 1 1 /16 and /8 in (1 and 3 mm).

Spine INCREASED NUCHAL FLUID SCAN If there is a greater than normal measurement of nuchal ﬂuid, the 12-WEEK SCAN health care team will discuss possible In this ultrasound implications with the parents. scan, the head is seen in proﬁle on the left. The placenta is above Larger nuchal fold In this fetus, the nuchal translucency the fetus, attached 1 by the umbilical cord exceeds /16 in (3.5 mm). to the fetal abdomen.

Ultrasound CHORIONIC VILLUS SAMPLING (CVS) transducer If there is an increased risk of the fetus having a genetic or Syringe and needle Monitors progress Extracts 30 mg of of syringe chromosomal disorder, the genetic material (karyotype) of chorionic tissue the fetus can be checked by CVS after 10 weeks and up to 15 weeks, when an amniocentesis is often preferred. The genetic material in the placenta is almost always identical to Fetus Urinary that in the fetus. Under ultrasound guidance, the long, ﬁne bladder needle of a syringe is passed through the abdomen into the placenta, and a miniscule quantity of placental tissue is removed and sent for analysis. The sample is always taken Vagina away from the cord insertion area. Sometimes the specimen has to be ABDOMINAL PROCEDURE taken by passing a ﬁne tube through Here, a needle is inserted through the the cervix and using gentle suction. abdominal wall (the transabdominal route), and cells are extracted away from the cord Cervix Amniocentesis and CVS both carry insertion. Ultrasound guidance ensures the a 1 in 100 chance of miscarriage. safe and accurate positioning of the needle. 115 MONTH 3 I KEY DEVELOPMENTS

SECTION THROUGH HEAD Although tiny enough to ﬁt in FETUS the palm of a hand, the fetus is developing rapidly. The relatively large head reﬂects the huge amount of internal growth but EARLY BRAIN DEVELOPMENT the brain still has to develop its characteristic folded appearance. The fetus’s brain develops throughout pregnancy. By the third month, major changes have already occurred. The thalami are by now jointly the largest element of the brain, acting as a relay station

CONCEPTION TO BIRTH TO CONCEPTION for the hemispheres. Beneath the paired thalami is the hypothalamus, which controls organ functions such as heart rate. Under the hypothalamus is the third ventricle, a chamber ﬁlled with circulating cerebrospinal ﬂuid (CSF) produced by the choroid plexus within each lateral ventricle. The cerebral hemispheres expand rapidly, although they are smooth at this stage, not achieving the familiar folded appearance until late in the second half of the pregnancy. This is only the start of brain development, which, unlike the other embryonic systems, undergoes major changes throughout pregnancy.

Cerebral Choroid hemisphere plexus Lateral ventricle

Thalamus

Hypothalamic sulcus

Hypothalamus

Third CEREBRAL HEMISPHERES ventricle The cerebral hemispheres form the upper smooth surface of the brain. They contain a choroid plexus with seaweedlike fronds. They are the sources of cerebrospinal ﬂuid, which protects the brain and the spinal cord.

FORMATION OF THE PITUITARY GLAND Infundibulum Rathke’s pouch detaches and migrates Anterior lobe of Posterior lobe of The pituitary gland forms from two parts—a to infundibulum pituitary gland pituitary gland downward fold of neural tissue (the infundibulum) and an upward projection (Rathke’s pouch) of an area close to the roof of the future mouth. Rathke’s Due to their different origins in the embryo, pouch the anterior and posterior pituitary lobes function independently, each producing different hormones. The posterior pituitary lobe is attached to the hypothalamus by the pituitary stalk, from which it receives Notochord neurotransmitters. These structures regulate oxytocin and antidiuretic-hormone release. The anterior lobe secretes the neurotransmitter beta-endorphin as well as seven hormones that are regulated through feedback mechanisms: EMBRYOLOGICAL SITES EARLY MIGRATION FINAL POSITION growth hormone, follicle-stimulating hormone, 1 The pituitary gland has two 2 During its upward journey, 3 The pituitary reaches its adult luteinizing hormone, prolactin, adrenocorticotropic lobes, each formed from separate Rathke’s pouch becomes detached position when the lobes are hormone, thyroid-stimulating hormone, and primitive areas: Rathke’s pouch from its original embryological joined and it is connected to the melanocyte-stimulating hormone. and the infundibulum. position, at the back of the throat. hypothalamus and cradled by bone. 116 EAR DEVELOPMENT The ear comprises three sections: an inner, middle, and outer ear (the visible or external part). The external ear develops from six small bumps on the skin (see p.150) and connects to the middle ear via the eardrum (tympanic membrane). Transmission along three tiny bones in the middle ear ampliﬁes the sound over 20 times to the inner ear. These bones have Latin names that describe their shape: malleus (mallet), incus (anvil), and stapes (stirrup). INNER EAR HAIR CELLS Hair cells in the inner ear can change their length This electron micrograph shows hair cells (pink) in the organ of Corti in the inner ear. in response to sound. The movement is converted They are fringed by microvilli (gray) in the into nerve impulses and transmitted to the brain. fetus, which are reabsorbed by adulthood.

Otic vesicle Developing Vestibulo- Semicircular ducts Forms the early semicircular cochlear Three tubes responsible inner ear ducts nerve for balance Cochlear duct Curled tube responsible for hearing Auditory ossicles

Meatal plug

Tubotympanic recess Future middle ear

Developing cochlear duct AT FIVE WEEKS AT 40 WEEKS 1 The three sections of the ear— 2 The inner ear not only processes inner, middle, and outer—start out sound within the coiled cochlear but also as completely separate elements judges head position and movement via that gradually merge together. three ﬂuid-ﬁlled semicircular canals.

Pigmented layer EYE DEVELOPMENT Forebrain of retina During the sixth week, a shallow pit infolds to form Produces optic cup Nourishes retinal neural cells the hollow lens. This is encircled by the optic cup, Lens placode an outpocketing of the primitive forebrain. Over the Thickened Neural layer next two weeks, lens fibers multiply and cause the ectoderm that is of retina precursor to lens Formed from lens to solidify. To accommodate this rapid growth, brain cells the optic stalk supplies blood to the lens (after birth Optic cup Most of this Lens fibers there is no blood vessel). The eyes are open at this structure forms Cells on lens wall the retina elongate to form stage. During the sixth week, eyelids appear, then lens fibers fuse by the eighth week and do not reopen until Optic stalk Lens vesicle 26–27 weeks. Tear-forming lacrimal glands lubricate Becomes optic Placode detatches, nerve when eye the eye, but do not fully function until six weeks forming the solid, is fully formed spherical lens after birth. The pigmented retina is very simple at AT 46 DAYS AT 47 DAYS this stage, but differentiates into distinct neural layers 1 The structure is becoming eyelike. The 2 The hollow lens vesicle close as the lens optic cup appears to almost encircle the fibers multiply. The optic stalk, which was a up to the time of birth. The optic stalk will become lens placode as it begins its separation from hollow structure, now contains nerve fibers the optic nerve by eight weeks. the skin surface to form the discrete lens. for its function as the optic nerve. 117 THE SKELETON The skeleton protects and supports the developing Maxilla fetus. It is initially composed of cartilage, but gradually ossifies into bone at varying rates so that the bones I THE SKELETON can expand to keep up with rapid fetal growth. THE DEVELOPING SKELETON The skeleton arises from the mesoderm cell layer. Bones form in two distinct ways. Most appear first as a soft cartilage framework that is later replaced with hard bone by the process of ossification. The flat bones of the skull miss the cartilaginous stage and arise directly as the mesoderm becomes ossified. In the bulk of the skeleton, cells called chondrocytes form the cartilaginous framework. The CONCEPTION TO BIRTH BIRTH TO CONCEPTION final shape of each bone results from a process of continuous bone formation, as calcium salts are laid down by cells known as osteoblasts; this is followed by remodeling through reabsorption of the bone matrix by osteoblasts.

Frontal bone Flat bones Facial bones and those of the Maxilla frontal skull are known as the ﬂat bones; bone tissue here Mandible Mandible forms without the presence of existing cartilage. Radius

Ulna

Humerus Long bones Tibia All limbs and girdles are known as long bones; bone tissue in these bones derives from a cartilage matrix. Fibula

Clavicle Femur 17-WEEK OLD FETUS Scapula The fetus’s skeleton and Axial bones joints have matured The vertebral Rib sufﬁciently for it to be column and ribs are able to perform a full the axial bones; 10-WEEK OLD FETUS Ilium range of movements. bone tissue derives Although still a simple cartilaginous framework, the This is when the mother from a cartilage Rib basic shape of each bone is complete. The bones becomes aware of her matrix. anchor muscle attachments, allowing simple movement. fetus’s movements.

LONG BONES All long bones, apart from the collarbone, form in the same way, Cartilaginous Secondary through a process called ossification, by which osteoblasts deposit epiphysis ossification center calcium salts. This process occurs in each bone at a different stage Appears within each epiphysis after of pregnancy and some, such as the breastbone, are not fully birth and during ossified until after birth. During primary ossification, a central collar adolescence of bone forms around the shaft, while cartilage remains at the ends. Even after birth, when secondary ossification occurs, the tips of Bone tissue the bones remain cartilaginous. To allow for childhood growth, Replaces cartilage ossification in long bones is not complete until the age of 20.

Bone collar Blood vessel Epiphysis Nutrient Surrounds network End of long bone artery Primary the diaphysis, Ensures the bone ossification strengthening receives nutrients Diaphysis center the bone for growth Shaft of long bone 7-WEEK OLD FETUS 10-WEEK OLD FETUS 12-WEEK OLD FETUS NEWBORN BABY 1 In the center of the shaft 2 With the arrival of a blood 3 The first part to be ossified is 4 Further ossification and (diaphysis), chondrocytes produce supply, chondrocytes are replaced the collar, which strengthens the remodeling continue after birth. collagen, in which calcium salts by osteoblasts and the gradual bone, encircling the diaphysis as The red bone marrow is a major are later deposited to form bone. process of ossification begins. it lengthens and thickens. site for blood cell production. 118 SYNOVIAL JOINTS THE SKELETON Most of the joints in the body are synovial-type joints. FLAT BONES The structure of a synovial joint allows a wide range of movement. In a synovial joint the ends of the bones The flat bones of the face and skull pair of skull bones (fontanelle) are protected by cartilage and separated by a fluid-filled arise from the direct conversion of remains open to allow for the capsule. Movement (articulation) can occur without mesoderm cells into osteoblasts, increase in head size due to brain the hard bones coming into contact and rubbing against

without an intermediate cartilage development. The spaces also allow I CONCEPTION TO BIRTH each other, which would erode their surfaces. By stage. This is called intramembranous the head to contract as it descends 15 weeks, all synovial joints have formed sufficiently ossification. The space between each through the birth canal during labor. to allow the fetus a full range of movement. Anterior Phalanges fontanelle Connective tissue Frontal bone containing fibroblasts Parietal bone UNDIFFERENTIATED STAGE Cartilage 1 Initial development involves nasal area portions of the soft cartilaginous Temporal bone bony framework transforming Site of tooth (differentiating) into connective formation tissue containing fibroblasts. Bone spicules from primary Dense Ulna ossification Cartilage connective tissue LATERAL VIEW OF THE SKULL AT 14 WEEKS Mandible Radius TISSUE DIFFERENTIATION 2 The fibroblasts form a dense layer of connective tissue—which becomes the joint—and stimulate Synovial joint further cartilage formation on One of many synovial joints, either side of this region. the knee enables movement Metatarsal of articulated bones. bones Articular cartilage (future joint lining) Femur Tibia FURTHER DIFFERENTIATION 3 Articular cartilage forms but joint movement (articulation) cannot occur until the dense connective tissue transforms into the fluid-filled synovial joint.

Tendons Vacuole in and ligaments connective tissue Both types of tissue are required SYNOVIAL CAVITY FORMS for the full range of 4 Vacuoles form in the dense skeletal movement; connective tissue and join up to ligaments join create the ﬂuid-ﬁlled synovial bones together and cavity. Ligaments that connect the tendons attach Fibula Cartilage muscles to bones. Most of the bones bones also start to appear. still contain a high proportion of soft Enclosed joint Ilium cartilage at this stage. Meniscus ligaments COMPLETED JOINT 5 The joint is now encased in a protective, ligamentous capsule, SPINAL DEVELOPMENT which means that the full range The development of the spinal cord and vertebrae To enable the spinal nerves to emerge from the of movement at the joint is are closely linked. Each somite (see p.99) gives spinal cord, the somites undergo resegmentation, now possible. rise to a dermomyotome portion that forms the in which they divide into two parts to allow the Joint capsule Synovial cavity skin and underlying muscles of the trunk, and a spinal nerve to emerge. Later, they rejoin their sclerotome part that forms the vertebral column. neighboring halves and evolve into vertebrae.

Rudimentary Sclerotome Vertebra Nerve connects spinal cord spilts into two with muscle MUSCLE DEVELOPMENT Spinal nerve root segments Nerve There are three types of muscles in the body: cardiac Fissure extends muscle, skeletal (voluntary) muscle, and smooth along (involuntary) muscle, such as the muscle of the gut. fissure Sclerotome The skeletal muscles of the trunk, and also the limbs, diaphragm, and tongue, develop from the somites in a Myotome similar way to the bones of the vertebral column. Each (muscles) Myotome somite has a myotome portion, from which the muscle arises. These portions are supplied by spinal nerves that allow the muscles to be controlled voluntarily. The SCLEROTOME FORMATION DIVIDING SCLEROTOME FUSED VERTEBRAE process starts during the seventh week of pregnancy, 1 As the nerve roots emerge 2 The fisure becomes a channel 3 The upper and lower parts of from the rudimentary spinal cord, in the center of each sclerotome, adjacent sclerotomes grow toward when the muscle groups start to gradually emerge each sclerotome begins to through which the nerve roots each other and fuse, becoming bony from the side of the future spine and extend around separate into two parts. A fissure emerge as they join a corresponding vertebrae. The spinal nerves join up the trunk and down into the limb buds. appears at the area of division. set of muscles (myotome). with their assigned muscles. 119 THE BONES OF THE HEAD These images show bones developing in the face and skull of a 14-week-old fetus. Bone appears red, and cartilage is shown in blue. The dark spaces separating the skull bones are the fontanelles, while the slender structures in the bones themselves are known as spicules.

MONTH 3 I KEY DEVELOPMENTS FETUS

LIMB FORMATION By the 10th week of pregnancy, all the limb joints have formed and simple movements are possible. The joints can be bent (ﬂexed) and extended, and the hands can be brought up to the face. Development

CONCEPTION TO BIRTH TO CONCEPTION of the upper limbs is slightly more advanced than that of the lower. Each limb starts as a bud and follows the same pattern of development, which involves a carefully sequenced program of cell growth and death. The bud gradually lengthens, and soft cartilaginous bones form within the tissues. This cartilaginous framework gradually hardens, each bone ossifying from the center outward (see pp.118– 119). The blood vessels of the limbs are easily seen through the thin, transparent skin, which has virtually no fat layer at this stage.

Paddlelike Heart upper limb Digital ray bud forms Liver Kidney

Webbed Stomach area Intestines HAND PLATE DIGITAL RAYS 1 The upper limb starts as a simple broad, 2 Five short projections materialize at short limb protruding from the surface at the edge of the hand plate and form the Umbilical six weeks. Smooth paddle-shaped hand ﬁngers. Development of the toes follows cord plates develop at the end of the bud. the same pattern about a week later. Urinary Early Cartilage bladder digits centers form Foot

Webbing Fully formed INTERNAL STRUCTURES Spine reduces digits Seen under a microscope, this thin section through a fetus EARLY DIGITS SEPARATED DIGITS shows the major organs. The neck is 3 The projections lengthen, and the cells 4 By the end of the eighth week all digits are short and the fetus remains curled with the between the fingers die and disappear. The distinct, but the overlying skin is thin and the chin on the chest. Although in this image the effect of this is to gradually reduce the ridges of each genetically determined fingerprint fetus may appear to be male, it is too early webbing between each pair of fingers. are not fully developed until 18 weeks. to accurately determine the sex of the fetus.

DEVELOPING INTESTINES Liver Aorta The intestinal tube continues to elongate and Stomach Cecum Intestines Future differentiate into specialized sections (see p.104). protrude into appendix umbilical cord Loops of Transverse The small bowel is too long to be accommodated intestine colon within the embryo’s abdomen, and it bulges into rotate the base of the umbilical cord. Taking its blood supply with it, the intestine rotates in the umbilical Lower loop of intestine forms Cecum is cord and completes the rotation as it returns to the concertina shape pulled down Continued abdominal cavity. The large bowel then becomes folding forms small instestine ﬁxed, holding the entire gut in place. This process Rectum starts at eight weeks and should be completed by ROTATION OF INTESTINES INTESTINES RETRACT INTO ABDOMEN 1 The simple intestinal tube rotates externally 2 The intestinal loop retracts into the abdominal 12 weeks. The gut is not yet functioning, and the in the base of the umbilical cord through 90°, in cavity, rotating 180° counterclockwise. The cecum is embryo is unable to swallow amniotic ﬂuid. a counterclockwise direction. pulled down with it and forms the ascending colon. 122 WEEKS 9–12

THE URINARY SYSTEM THE SEX ORGANS At first the bladder and lower bowel (rectum) open into a common In both males and females, the development of the urinary system opening called the cloaca. This separates into two, dividing the is closely linked with the formation of the internal sex organs. Germ bowel from the bladder. A short ureteric bud grows upward on cells in the yolk sac move into the embryo during the sixth week each side from the bladder to fuse with the primitive kidney at five to lie on the urogenital ridge close to the developing spine of the weeks. Over the next four weeks, each kidney gradually ascends as embryo. These cells stimulate formation of either the ovaries (female) it matures and lengthens the ureter on its journey upward. Branching or testes (male). Close by, a new pair of ducts form (mullerian of the ureter within the kidney forms the collecting system into ducts), which will disappear in the male but develop into the which the filtered urine is passed. This process is not complete until fallopian tubes, uterus, and upper part of the vagina in the female. 32 weeks, when approximately 2 million branches have formed. The separation into male or female is governed by genes on the Y

chromosome. Embryos without these Liver Mesonephric genes develop as females and duct those with, become males. Somites

Ureteric bud Mesonephric Cloaca (primitive kidney) Sex cells migrate duct from umbilical cord to genital ridge Mesonephros Urogenital sinus Urorectal (primitive bladder) Mullerian septum INDIFFERENT GONAD STAGE duct Rectum The male and female gonads appear similar at this stage but the developmental pathway they Genital ridge DIVIDING CLOACA will follow is predetermined by the presence or 1 The urorectal septum moves downward to absence of the Y chromosome. Kidney the cloacal membrane to separate the bladder (and the unformed tube joining the bladder to the outside—the urethra) from the rectum. Major Minor Renal calyx calyx Mullerian duct Follicle Fimbria pelvis developing cells

Urinary Ureter Mesonephric duct Future bladder degenerating ligaments

Sex cells form future ovarian Urorectal Ureter follicles septum divides bladder and Rectum rectum EARLY FEMALE SEX ORGANS DEVELOPING FEMALE SEX ORGANS THE DEVELOPING KIDNEY In the absence of a Y chromosome, the The upper part of the mullerian duct has BLADDER AND RECTUM FORMATION Branches of the ureter form the indifferent gonad defaults into the female formed the ﬁmbrial end of the fallopian 2 The process of separation is complete by major calyces that divide into state, forming an ovary containing millions tube. Its lower portion will form the rest the seventh week. The rectum is not open—it the minor calyces. These branch of oocytes that remain inert until puberty. of the tube, the uterus, and upper vagina. is covered by a temporary thin membrane— further to collect the urine but this will disappear over the next 10 days. from the kidney tissue. Mullerian duct Tunica Vas deferens degenerating albuginea developing

Mesonephric THE LYMPHATIC SYSTEM duct As liquid leaks out from the bloodstream to bathe the cells of the body, excess fluid (lymph) needs to be returned to the circulation. This is achieved by a series of sacs and, later in development, channels, which are together Sex cells known as the lymphatic system. This system develops in parallel with the form early Future embryonic vascular system of blood vessels. The lymphatic system forms seminiferous seminiferous from a pair of upper lymph sacs during the fifth week, which remove lymph tubules tubules from the upper body. The following week, four lower sacs arise that drain the lower body. Further connections and modifications between these sacs EARLY MALE SEX ORGANS DEVELOPING MALE SEX ORGANS result in the majority of the lymph draining into the upper body thoracic In each testis germ cells form Sertoli cells The mullerian duct is now a tiny remnant that nurture developing sperm. Leydig on top of the testis. The mesonephric duct, which enters into the subclavian vein (a left-sided neck vein). cells in the gonad produce testosterone duct links each testis to the urethra via the to stimulate further male development. seminiferous tubules and vas deferens. 123 This 3D ultrasound scan shows a 13-week-old fetus This 2D ultrasound scan shows a 20-week-old fetus This photograph of a five-month-old fetus shows touching its face with its hands. All of its joints are in the uterus. A scan is usually performed at this time the developing facial features. The eyelids remain now present, allowing for a range of movements. to check that the fetus is growing as expected. fused until the beginning of the third trimester.

TRIMESTER 2 MONTHS 4–6 I WEEKS 13–26

The second trimester of pregnancy is a time of continuing growth and development. All the body systems are in place, but the fetus is not yet capable of independent life.

The maternal discomforts of the first trimester, such as morning mother-to-be is known as “quickening” and usually occurs during sickness and fatigue, start to settle at the beginning of the second the fifth month, but it may be felt earlier if the woman has had a trimester. Steadily increasing blood volume and a more dynamic child before. Over the course of the second trimester, the fetus will circulation give the mother-to-be a healthy glow. The top, or more than triple in size, and its weight will increase by around 30 fundus, of the uterus should rise above the pelvis in the fourth times. During the first half of the second trimester, the fetal brain and month, making the pregnancy obvious. The fundus of the uterus will nervous system are still undergoing a critical period of development. 3 continue to rise at a rate of approximately /8 in (1 cm) per week. This The second half of the second trimester sees the rapid growth of the measurement gives a good estimation of the week of pregnancy, so fetal body and limbs, while the head grows at a relatively slower rate. that, for example, at 20 weeks of pregnancy, the fundal height will As a result, the proportions of the fetus look more like those of an be around 8 in (20 cm). The first movement of the fetus felt by the adult by the end of the trimester.

TIMELINE

WEEK 13 WEEK 14 WEEKS 15–16 WEEKS 18–19 Maternal nausea, The placenta starts a Amniocentesis is a procedure that involves The mother-to-be usually feels if present, now usually second wave of growth extracting and analyzing a sample of amniotic the first fetal movements or decreases. that will anchor it more fluid. It is typically performed between weeks “quickening” around this time. firmly to the lining of 15 and 16, but it is usually offered only if there the uterus. is a significant risk of the fetus developing a serious condition. MOTHER

WEEK 13 WEEK 14 WEW EK 15 WEEK 16 WEEK 17 WEEK 18 WWEEK 19 MONTH 4 MONTH 5 WEEK 13 WEEK 14 WEEK 15 WEEK 16 WEEK 17 WEEKS 18–19 Myelin-sheath The spine The first hair The fetus starts In a female fetus, The eyes and ears have arrived development starts straightens out. follicles form. to make regular the uterus and in their final positions. in the peripheral The body is starting The skin thickens breathing vagina form. By the end of the 18th week, nervous system. to look in better and differentiates, movements. The bronchioles all of the milk teeth buds have FETUS The first white proportion with forming three and alveoli start to formed, 10 in the upper jaw blood cells are the head. distinct layers. develop in the lungs. and 10 in the lower. produced.

124 The fetus’s proportions have changed by the end of the trimester, with the head, torso, and legs each accounting for roughly one-third of the total length of its body.

WEEKS 20–21 WEEKS 23–24 WEEK 25 WEEK 26 The mid-pregnancy scan is usually carried A cervical-length scan may be performed at A prenatal visit usually At 26 weeks, the out at around 20 weeks to check that this time to predict the risk of premature occurs around this time height of the top, or the fetal organs and limbs are developing delivery. The risk increases if the cervical to check urine, blood fundus, of the uterus 3 normally. This scan also helps date the length reduces to less than /4 in (2 cm). pressure, and to see if is approximately pregnancy accurately. the fetus is growing as 10 in (26 cm). expected.

WEEK 20 WEW EK 21 WEEK 22 WEEK 23 WEEK 24 WEEK 25 WEEK 26 MONTH 6 WEEK 20 WEEK 21 WEEKS 22–23 WEEK 24 WEEKS 25–26 True awareness is The fetus starts to The bones in the Fingernails and The barrier The smooth surface of the brain not thought to lay down some fat inner ear harden, toenails start to between the starts to wrinkle as the cerebral start developing beneath its skin. improving the fetus’s appear at the base bloodstream cortex continues to develop. until now, although The anal sphincter sense of balance. of the nail beds. and the alveoli The adrenal gland starts to release it may occur earlier. becomes fully The skin starts to thins, making gas steroid hormones, to help prepare functional. develop ﬁne, downy exchange possible the baby for the stresses of birth. hair, called lanugo. after birth.

125 MONTH 4 I WEEKS 13–16 The fourth month marks the beginning of the second trimester. The uterus has expanded to reach the top of the pelvis and can be felt above the pubic bone. This means the pregnancy will soon start to show.

WEEK 13 WEEK 14 Some pregnancy symptoms, such as morning sickness, are Changes in maternal blood flow and blood volume often give improving but others, such as constipation and indigestion, a mother-to-be a healthy color, which is referred to as the may take their place. In the fetus, sweat glands are appearing pregnancy “glow.” Combined with an expanding abdomen, and hair can be seen on the scalp. A clearly defined neck has this glow is an external clue to her pregnant state. The fetus formed, and the chin is more upright. The head seems large is now growing rapidly, and over the next three weeks, it will for the body, representing half the crown-rump length. The double in size, as fat, in addition to glucose, is now used as an arms have grown in proportion to the body, but the legs energy source. As a result, the fetal body is now longer than still look too small. The muscular and nervous systems are the head. The placenta still acts as a kidney to control the fluid developed enough to allow uncoordinated limb movements. balance, but the fetus’s urinary system is now sufficiently The spinal cord extends the full length of the vertebral canal, developed to produce tiny amounts of very dilute urine. and nerve cells in the brain and peripheral nervous system are The bladder fills and contracts every 30 minutes, but it can increasing and migrating to their proper places. Also, nerve only hold a small amount of fluid—less than a teaspoonful. fibers are slowly being insulated with a fatty myelin sheath. Miniature toenails are now growing in the nail beds.

FORMATION OF THE NECK This 3D ultrasound of a 13-week-old fetus shows how the neck has lengthened. The chin no longer rests on the chest.

GROWTH SPURT This photograph shows the enlarged liver (dark mass), which produces red blood cells that enable rapid growth to occur.

GROWTH OF SPINAL CORD FETAL HAND BONES Vertebrae can be seen around In this scan, the red areas show the spinal cord in this ultrasound where hard bone is forming scan. The crown–rump length is in the ﬁnger bones (phalanges) indicated by the blue crosses. and hand bones (metacarpals).

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WEEK 15 WEEK 16 As fetal growth accelerates, amino acids are extracted from The fetus’s face looks obviously human, with eyes in the the mother’s blood to build muscles and organs in the fetus. correct forward-looking position and ears moving up toward The fetus drinks amniotic fluid, which acquires flavors from their final position. The thyroid gland is descending from the the mother’s diet. The lungs are expanding and producing base of the tongue into the neck. The fetus is now almost equal small amounts of mucus. The external sex organs are now in size to the placenta, and a second wave of placental growth visible, and it may be possible to identify gender from an now anchors it more firmly to the uterus as blood flow ultrasound scan. During this month, hundreds of thousands to the fetus increases. Mothers-to-be are offered a number of eggs are forming within the ovaries of a female fetus. At of screening tests, including amniocentesis, in which a sample the same time, the ovaries move down from the abdomen of amniotic fluid is collected to analyze fetal cells. This into the pelvis. The umbilical cord is thickening and procedure can be performed from 15 weeks, but is usually lengthening as it carries more and more oxygenated blood, undertaken between 15 and 16 weeks. It is normally only rich with nutrients, from the placenta to the fetus and returns offered to mothers with a higher than normal risk of a baby deoxygenated blood and wastes to the mother’s body. with chromosomal abnormalities such as Down syndrome.

DEVELOPMENT OF OVARIES FETAL HEART MONITORING This light micrograph shows A fetal heart rate monitor easily primordial cysts (follicles) of assesses how rapidly the fetal a fetal ovary; within each cyst, heart is beating. In this image, an egg is visible (dark dot). the rate is 165 beats per minute.

AMNIOCENTESIS Guided by ultrasound, a long, ﬁne needle is inserted through the mother’s abdomen into the uterus to collect amniotic ﬂuid.

LINING OF THE AMNION A scanning electron micrograph of the surface of the amniotic sac shows the cells that encircle the amniotic ﬂuid.

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MOTHER AT 16 WEEKS MONTH 4 I WEEKS 13–16 A fall in blood pressure and rising hormone levels are MOTHER among the significant changes MOTHER AND FETUS this month. The hormone 68 beats per minute changes are thought to take away the morning sickness 104/66 The fourth month of pregnancy marks the beginning of that was a common feature of the first three months. 8 pints (4.5 l) the second trimester. Early symptoms of pregnancy, such as fatigue and nausea, have usually started to subside, the Blood volume and pressure pregnancy is starting to show, and women often feel in the Blood volume increases significantly this month, while 30% best of health and appear to be “blooming.” A number of blood pressure falls slightly, Levels of human chorionic screening tests may be offered during this month to ascertain after which it continues to gonadotropin (hCG) rise until the birth. whether there is a risk of developmental abnormalities in the blood fall by 30 percent this month. occurring in the fetus. If there is a high risk, amniocentesis can Uterus expansion be performed at the end of this month to detect conditions such The uterus starts to expand Increasing blood flow to the into the abdomen, causing the as Down syndrome. The fetus is still growing rapidly and fine, skin causes the distinctive abdominal wall to stretch to pregnancy glow. downy hair (lanugo) starts to cover the skin. It starts to produce accommodate it. This results in the first sign of a pregnancy small amounts of urine, which pass out of the urethra and into “bump.” Although they usually The pregnancy first starts to the amniotic fluid. The fetus’s facial features continue to develop, appear later in pregnancy, become obvious during this stretch marks may develop now month, depending on the and its proportions begin to look more like those of an adult. as a result of this expansion. mother’s weight and build.

12345678910111213 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 STATISTICS FETUS 158 beats per minute 41⁄2 in (12 cm) 31⁄2 oz (100 g) 100% The fetus doubles in size during the fourth month of pregnancy. 30 minutes The fetus’s bladder empties every 30 minutes, contributing a small amount of urine to the amniotic ﬂuid.

The fetus’s heartbeat can be heard in the fourth month with a hand-held doppler ultrasound machine. The fetus’s heart rate is over twice as fast as the mother’s. Chorionic villi Perimetrium

Maternal artery Endometrium

Maternal vein Myometrium

Taste buds mature By the end of the fourth month, the fetus’s taste buds Cerebellum development are structurally very similar The cerebellum is undergoing a to those of an adult. critical period of development; by the 15th week, ﬁssures and ridges have appeared, and the deep cerebellar nuclei have formed from migrating neurons. Umbilical cord

Gender now visible Skin layers The sex of the fetus is Skin differentiates apparent in the middle into three layers—the of the fourth month, epidermis, the dermis, but it is not usually and subcutaneous fat. revealed to the parents until the mid-pregnancy ultrasound at 20 weeks. Appearance of lanugo Amniotic ﬂuid A ﬁne, downy hair starts to grow all over the body.

Blood-cell production The ﬁrst white blood cells are produced in the liver, thymus, and spleen but are not effective at combating infection.

Mucus plug Production of urine Tiny quantities of very dilute urine Cervix start to be produced by the kidneys Amnion this month; it is released into the MULTI-SYSTEM DEVELOPMENTS urinary bladder, along the urethra, The brain undergoes a critical period Vagina Chorion and into the amniotic ﬂuid. of development this month, with 100–250,000 brain cells forming every minute. The reproductive system is developing to the point at which the sex of the fetus is obvious. Facial features are developing rapidly, and the eyes have moved to their ﬁnal position. MONTH 4 I KEY DEVELOPMENTS

MOTHER

STARTING TO “SHOW” MORNING SICKNESS The top (fundus) of the womb has now risen well SUBSIDES above the pelvis, and it can be easily felt during an Morning sickness, which abdominal examination. Whether a woman looks affects around seven out of ten

CONCEPTION TO BIRTH TO CONCEPTION pregnant at this stage depends partly on her height women, starts to ease after the and build and partly on the amount of weight she ﬁrst trimester and has usually gains. Every pregnancy is different, even for the disappeared by the 14th week BLOOD LEVELS BLOOD same woman. In general, however, women who of pregnancy. A small number KEY are taller than average, overweight, or in their of women continue to suffer ESTROGEN PROGESTERONE ﬁrst pregnancy do not tend to “show” as early as throughout pregnancy. The hCG women who are shorter, of a more slender build, exact cause is unknown, but

or in a second or subsequent pregnancy. it has been linked with low 40 8121620 blood sugar, increased PREGNANCY (WEEKS) VISIBLE BUMP secretion of bile, and raised LINK WITH HORMONE LEVELS The waistline has become noticeably thicker levels of some hormones, Blood levels of the hormone, human and the breasts are enlarging, although the chorionic gonadotropin (hCG), have fallen pregnancy is not obvious and can easily be namely estrogen and human signiﬁcantly by 12 weeks, which is possibly hidden beneath loose clothing. chorionic gonadotropin (hCG). why morning sickness resolves at this time.

PREGNANCY “GLOW” Skin is normal The healthy “bloom” of pregnancy begins around temperature BLOOD PRESSURE CHANGES the fourth month and results from an increase in Blood pressure falls until the middle of the the volume of blood in circulation and the dilation Blood vessel carries second trimester, where it starts to rise again. of blood vessels. This diverts more blood to the a normal amount of blood Posture has a significant impact on blood skin to give her a glowing appearance. Dilation of pressure. When a pregnant woman lies down, blood vessels is due to the effects of progesterone, her growing uterus presses against the large levels of which increase significantly during vein situated behind the abdominal cavity. As pregnancy. Although blood volume rises by a result of this, blood pressure is affected by whether the woman is sitting, lying on her 45 percent during pregnancy, the mass of red Gland produces minimal sweat back, or lying on her left side. It is therefore blood cells within the blood only increases by unless exercising important that a woman’s posture is the same 20 percent. Most of the increased blood volume each time her blood pressure is recorded so is due to fluid retention. This dilution causes NORMAL WIDTH OF BLOOD VESSELS that values can be correctly compared. hemoglobin levels to fall. At one time, this led to Blood flow to the skin surface is normally 120 determined by the temperature, exercise, frequent diagnosis of anemia, and many pregnant and lifestyle factors such as alcohol intake. women were treated with iron tablets. Doctors 100 now realize blood dilution is natural in pregnancy, Systolic Sweat produced (maximum pressure) and iron tablets are no longer routinely prescribed. and skin is flushed 80 50

40 More blood travels 60 through dilated (mmHg) PRESSURE BLOOD Non Diastolic vessels as blood pregnant (minimum pressure) 30 volume increases 40 40 8 12 16 20 24 28 32 36 40 20 GESTATION (WEEKS)

PERCENTAGE CHANGE PERCENTAGE 10 BLOOD PRESSURE READINGS KEY Sweat gland more Both systolic (higher) and diastolic SITTING active to combat (lower) readings are consistently LYING FLAT 0 ON BACK 0 84 12 16 20 24 28 32 36 40 high temperature reduced when a woman lies on GESTATION (WEEKS) her back, compared to sitting INCREASING BLOOD VOLUME KEY DILATED BLOOD VESSELS down. Whatever the posture, Total blood volume and amount pumped CARDIAC During pregnancy, blood ﬂow to the skin blood pressure is measured with OUTPUT the arm strap level with the heart. by the heart (cardiac output) increase from TOTAL BLOOD increases due to greater blood volume and early pregnancy to peak around 32 weeks. VOLUME dilation of blood vessels (vasodilation). 130 FETUS WEEKS 13–16

SCREENING TESTS SCREENING TESTS FOR DOWN SYNDROME A variety of screening tests is usually offered in the fourth month to assess fetal development. A number of tests are used to predict the risk of Down syndrome, all of which measure the levels of various While some abnormalities can be identiﬁed hormones and proteins in the blood. A “false positive” by ultrasound scans, others can only be picked result suggests a high risk for Down syndrome, which up through blood tests and more invasive is shown to be incorrect following a diagnostic test. procedures such as amniocentesis (see below). The decision to have a screening test is personal. METHOD OF TIMING DETECTION FALSE SCREENING (WEEKS) RATE (%) POSITIVE Before deciding whether to go ahead, it is RATE (%)

important to obtain as much information as Triple 15–20 69 5 possible about the risks test ANALYZING A and beneﬁts. Discussing BLOOD SAMPLE Quadruple 15–20 76 5 Down syndrome and implications of a high-risk test several other fetal result should be part of the abnormalities can Combined 11–13 85 5 be detected decision process. Genetic test by measuring the counselors, doctors, and levels of different other professionals can help Integrated 11–13 85 1 placental hormones test 15–22 in the blood. parents make a decision.

Ultrasound Amniotic fluid AMNIOCENTESIS transducer After collection, Ultrasound identifies amniotic fluid is sent This is a procedure in which a small sample of the safest point of away for analysis. amniotic fluid is removed from the uterus and entry and helps guide Depending on the the operator during test, results can take then analyzed in a laboratory. A long, fine needle collection of fluid. up to two weeks. is inserted through the abdominal wall; an Syringe ultrasound transducer is used to make sure the needle is being directed into the right place. 3 Approximately 4 teaspoons or /4 fl oz (20 ml) is extracted from the sac surrounding the fetus. This fluid contains live fetal skin cells, the genetic material of which can be analyzed. Amniocentesis can be carried out from 15 weeks onward, but it is usually performed between 15 and 16 weeks. Amniotic sac The puncture The procedure is generally only offered to women quickly heals, Pubic assessed as having a higher than normal risk of and amniotic bone fluid is soon having a baby with chromosomal abnormalities replenished. such as Down syndrome (see p.237). Bladder Amniocentesis accurately identifies the number of Placenta chromosomes in fetal cells and can also determine whether the fetus is male or female. Later on in Uterus pregnancy, amniocentesis can predict fetal lung The needle maturity and diagnose infections. penetrates the muscular wall of the uterus. Mucus plug EXTRACTING AMNIOTIC FLUID Umbilical During this procedure, great care must cord be taken to make sure the collecting Vagina needle does not damage vital structures, including the placenta. Ultrasound scanning is used to guide the needle to an area where it is safe to take a Cervix sample of fluid. 131 MONTH 4 I KEY DEVELOPMENTS

Cerebellum forms Midbrain External DEVELOPMENT OF THE BRAIN between midbrain germinal and hindbrain By the fourth month, the brain is the size of a kidney layer Midbrain bean, making it fairly large compared with the rest Hindbrain of the body. Brain cells originate from cells that lined Marginal layer the central cavity of the neural tube. At this time, Purkinje these cells multiply at the astonishing rate of 100,000— cells 250,000 per minute, and migrate from the tube into the Internal germinal brain swellings. Every time the fetus moves, electrical Ventricular layer layer

CONCEPTION TO BIRTH TO CONCEPTION messages pass from muscles to the developing brain. Forebrain This helps stimulate development of the cerebellum LAYER DIFFERENTIATION (which controls posture and movement) and the 1 By 12 weeks, rapidly multiplying brain cells, including Purkinje cells, involved in regulating motor cortex of the muscle movements, move to the surface to cerebral hemispheres, LOCATION OF EMERGING CEREBELLUM form the external germinal layer of gray matter. which are involved in Midbrain Gray the future initiation Primary matter of voluntary muscle fissure White movements. matter Brain cells Choroid plexuses migrate outward Internal from internal germinal The cerebrospinal fluid that germinal layer layer bathes the nervous system forms in the choroid plexuses. Deep cerebellar Brain cells nuclei, formed Choroid migrate inward Choroid by migrating FETAL BRAIN AT 13 WEEKS plexus Ventricular from external plexus neurons germinal layer This ultrasound scan of the layer brain of a 13-week fetus shows FORMATION OF PRIMARY FISSURE DEVELOPMENT OF FISSURES AND RIDGES a choroid plexus in the left 2 By 13 weeks, the cerebellum has started 3 By 15 weeks, the cerebellum has developed and right brain hemispheres. to fold in on itself, forming a large fissure. many more folds. Contained within these The dark areas above are the Developing brain cells continue to travel convolutions are a number of specialized fluid-filled lateral ventricles. outward from the internal germinal layer. cells that are involved in fetal movements.

DEVELOPMENT OF THE URINARY SYSTEM THE PRODUCTION OF URINE The urinary system starts to develop early in the fourth week of gestation in the lower pelvic region of the embryo. The kidneys start The fetal kidneys start to produce small amounts of to form in the fifth week. Between this time and the fourth month, urine around the beginning of the fourth month of the kidneys shift position dramatically, from the pelvic region to the development. The tiny bladder holds only a few milliliters of fluid, and dilute urine is regularly released into the abdominal region. In the fourth month, the kidneys are capable of amniotic fluid as shown below. As pregnancy progresses, producing urine, which is expelled from the kidneys and released urine is produced in larger quantities and becomes more along the ureters to the urinary bladder before exiting via the concentrated. The fetus drinks and recycles this fluid. urethra. In the female fetus, the entrance to the vagina and the Penis urethral opening are part of the same structure until the sixth month.

Urachus Kidney Kidney

Urethra Fallopian Urinary tube bladder Testis

Ovary Penis Ureter Clitoris Ductus Uterus Spongy deferens Vagina urethra Rectum Rectum

URINATING INTO THE AMNIOTIC FLUID MALE FETUS AT 14 WEEKS FEMALE FETUS AT 14 WEEKS This Doppler ultrasound scan shows a male fetus (on In the male, development of the In the female, the urinary and reproductive the left) urinating (highlighted in blue, white, and red) reproductive and urinary systems is systems develop separately. The short through his penis into the amniotic ﬂuid. closely linked because both systems share urethra exits from the bladder at the the same exit from the body via the penis. urogenital sinus, in front of the vaginal plate. 132 CHANGING APPEARANCE WEEKS 13–16 Growth at this time is rapid, and the facial features of the fetus are developing quickly. Although the fetus still has a relatively large, bulging forehead, its eyes have moved from the sides of the head toward the front. This dramatically changes its facial appearance, and although the eyelids have not yet fully developed and remain fused, the fetus is beginning to look recognizably human. The outer ears have formed, and it has a button nose. The arms, wrists, hands, and ﬁngers are developing more quickly than the lower legs, feet, and toes. The skin is thin and looks red as a result of the presence of many tiny blood vessels that are clearly visible.

DEVELOPMENT OF FACIAL FEATURES A photograph taken inside the uterus shows the fused eyelids of a fetus at four months. The umbilical cord ﬂoats behind.

LANUGO HAIR The delicate skin of a four-month-old fetus is covered with ﬁne lanugo hair, which is present even on the developing ear lobe.

THE FORMATION OF THE GENITALS THE FORMATION OF THE UTERUS In early embryonic development, the male and female genitals The uterus and cervix form from the fused ends of the mullerian look identical—this is known as the indifferent stage. The baby’s ducts (see facing page). By the fourth month, the division between sex cannot be easily identiﬁed until the fourth month of gestation. In the two fused tubes has disappeared completely, leaving behind a a male, two ridges (the labioscrotal swellings) fuse along the midline hollow, muscular tube—the uterus. The vagina forms separately to form the scrotum. A rounded bump (the genital tubercle) elongates from a ﬂat, circular collection of cells called the vaginal plate. to form the penis. In a female, the labioscrotal swellings are separate These thicken and grow in a downward direction to form a and form the labia (lips) surrounding the entrance to the vagina. solid cylinder. This structure starts to hollow out so that, by around 16 weeks’ gestation, the vagina has fully formed. EARLY INDIFFERENT STAGE Urogenital Genital 1 The genital tubercle and fold tubercle labioscrotal swelling appear at Uterus around four weeks, and appear Labioscrotal Cloacal swelling membrane identical in males and females. Urinary bladder Phallus Uterus LATER INDIFFERENT STAGE 2 By six weeks, a division Urogenital Anal Pubic Fornix has formed that separates membrane membrane bone the developing anus from Vagina the urogenital membrane. Clitoris

Clitoris AT 14 WEEKS Prepuce Urethra 3 Midway through External External Vagina the fourth month of urethral urethral Hymen gestation, the sex of Fused orifice orifice the external genitals labioscrotal UTERUS AT 14 WEEKS UTERUS OF A NEWBORN Scrotum Posterior has become obvious. swellings labial 1 The uterus now forms a long tube, and 2 The uterus is naturally slightly The urogenital commissure the vagina is starting to hollow out. At 14 curved and tilts forward within the membrane has fused weeks, the lower part of the vagina opens pelvis. The lower end of the vagina Anus in a boy, but forms Hymen into the urethral opening, but they soon is protected by a thin, incomplete the hymen in a girl. MALE FEMALE develop separate entrances. membrane called the hymen. 133 MONTH 5 I WEEKS 17–21 During the fifth month of pregnancy, the fetus grows rapidly in length and may double in weight. The growing uterus now makes the pregnancy more obvious, and the mother may become more aware of the life that is growing within her uterus.

WEEK 17 WEEK 18 For the first time, the fetus has now grown larger than the Some pregnant women notice skin pigment changes on placenta that anchors it to the womb lining. Its proportions their face and abdomen. These changes are caused by the are changing, although the head, hands, and feet still seem hormones produced during pregnancy and will fade after too large for the body. The legs and trunk continue to grow delivery. The mother’s breasts are becoming larger, and at different rates, and body proportions will slowly continue her nipples tend to become darker and more pronounced to become normal. The nervous system is developing apace, as pregnancy progresses. Small lubricating glands, called and a fatty myelin sheath begins to form around some Montgomery’s tubercles, may appear around the nipples, nerves. This process, which is known as myelination, and large veins may be visible in the breasts. The fetus's facial continues through the rest of fetal life and early childhood. features are well formed, and it can produce facial expressions, Myelination helps speed up electrical communication between such as smiling, grimacing, and frowning. It swallows amniotic the body and brain. The fetus can now move its arms and fluid regularly and will often hiccup strongly enough for the legs quite vigorously, and as myelination continues the limb mother to feel. The fetal skin is transparent and paper thin, movements gradually become better coordinated. and fingerprints are forming ridges on the tips of the fingers.

FACE DEVELOPMENT This photograph shows a ﬁve-month-old fetus with mouth, nose, eyelids, and eyebrows fully formed.

PRACTICE-BREATHING This scan shows fetal breaths causing amniotic fluid to flow in all directions. Fluid (in red) is seen flowing out of the mouth.

LOWER LIMB DEVELOPMENT The legs develop more slowly than the upper limbs, but by 17 weeks the fetal foot is well formed, with ﬁve distinct toes.

BREAST CHANGES The areola develops glands called Montgomery’s tubercles, which secrete a scented oil that attracts the baby to the nipple.

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WEEK 19 WEEK 20 By the end of the 19th week, the full complement of milk teeth Between 18 and 20 weeks, a mid-pregnancy scan is carried buds have formed—ten in the upper jaw and ten in the lower out in order to check that the fetus's limbs and organs are jaw. These tiny teeth buds lie dormant beneath the gums until developing correctly. The external genitals are now visible, and some time after birth. The fetus's eyebrows and scalp hair are the sex of the fetus has become more obvious on ultrasound becoming visible, but the eyelids are still firmly fused together scans. In a female fetus, the ovaries have descended from the to protect the delicate developing eye beneath. The fetus abdomen into the pelvis. In a male fetus, the testes are also continues growing rapidly, and the top of the uterus grows descending, but they have not yet passed out of the body upward by around 3/8 in (1 cm) per week. The top of the into the scrotum. The ability of the fetus to interact with its uterus is now almost level with the mother’s belly button environment is increasing due to the development of the (navel or umbilicus). The cartilage that forms the blueprint for nervous system. Amazingly, the fetus can already detect a the fetal skeleton is starting to harden in some places to form number of sounds and tastes, and nerve pathways that carry areas of bone. This process, known as ossification, continues information about pain, temperature, and touch are starting after birth to allow childhood growth. to develop. The first tentative sparks of awareness are in place.

DEVELOPING TEETH BUDS MID-PREGNANCY SCAN The milk tooth bud is beginning The 20-week ultrasound scan to resemble an actual tooth. checks the major fetal organs The developing adult tooth and body systems to ensure bud can be seen at the top left. they are developing normally.

EXPANDING BUMP The pregnancy is nearing the halfway stage, and the top WEEK 21 of the uterus (fundus) grows The fetus is growing steadily, and fat is laid down beneath upward at an astonishing rate. the skin. Although the skin is still wrinkled and pink, it has developed two layers and is less transparent. Palm creases and ﬁngerprints are apparent. Small amounts of meconium— a solid, green–black substance comprising gut lining cells and waste from swallowed amniotic ﬂuid—pass through the gut. The anal sphincter starts to function at around 21 weeks.

FORMATION OF BONE This ultrasound scan of an open fetal hand highlights the bone (white) that is forming within each individual digit.

135 CONCEPTION TO BIRTH

MOTHER AT 21 WEEKS MONTH 5 I WEEKS 17–21 This is often the first month that the mother feels the MOTHER fetus moving. The mother’s MOTHER AND FETUS breasts have now grown 72 beats per minute noticeably larger, in preparation for lactation. 105/69 The first movement of the fetus felt by the mother—known 8 pints (4.6 l) as quickening—usually occurs this month. The mother may start Breast changes to notice changes in skin pigmentation, such as the appearance The nipples and areolae of a dark line (linea nigra) running from the navel down to the become progressively darker, and small lubricating glands 20% pelvis and brown patches (chloasma) on the cheeks. Both of appear as tiny bumps The mother’s blood volume these pigment changes are thought to result from hormone around the areolae. is now 20 percent higher changes and usually disappear or lighten after the birth. The than it was before pregnancy. mother’s breasts are enlarging, and the nipples and surrounding Melanin production The first movement of the areolae darken. The mid-pregnancy scan, usually performed Increasing production of the fetus felt by the mother is pigment melanin can lead at 20 weeks, detects any major fetal abnormalities, checks the called quickening and usually to a thin, dark line appearing occurs this month. position of the placenta, and reveals the sex of the baby. The between the navel and the lower abdomen. Dark From the fifth month fetus starts to move with increasing regularity and begins to patches can also appear on hiccup. A fatty layer is starting to insulate the nerves, which the face, forming what is onward, the top of the sometimes known as the uterus (the fundus) rises at a makes the fetus’s movements faster and better coordinated. “mask” of pregnancy. rate of 3/8 in (1 cm) per week.

1234567891011121314151617 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 STATISTICS FETUS 150 beats per minute 10 in (26 cm) 12 oz ( 350 g) 50:50 For the ﬁrst time in the pregnancy, the fetus is the same weight as the placenta. 90% The fetus now has a water content of 90 percent. This reduces to 70 percent by birth and 60 percent by adulthood.

The mid-pregnancy ultrasound scan checks that the fetus is growing as expected, and detects major anomalies or defects. The sex of the fetus is now apparent on this scan. Perimetrium Myometrium Chorionic villi Endometrium

Maternal artery Myelination Fatty outer coatings now start Maternal vein to form around the nerves, which play a vital role in the coordination of movement; this process continues throughout fetal life and into childhood.

Tooth buds Amniotic ﬂuid Milk, or deciduous, teeth buds have now developed.

Fingerprints Amnion These start to form from the dermal ridges on the tips of the ﬁngers; toe prints also start to appear. Chorion

Ears and eyes Umbilical cord These have now moved into their ﬁnal positions.

Increasing movement Lung development Recent motor-neuron Bronchioles (the maturation allows a wider furthest branches of range of limb movements. the airways from the trachea) are forming in the lungs.

Fat production Digestive system A layer of fat is laid development down under the skin; The anal sphincter the skin also starts becomes fully to become less functional, but the translucent. fetus will not pass its ﬁrst stool until birth. Eggs and sperm In a female fetus, the ovaries will contain a BODY SYSTEM DEVELOPMENTS remarkable six million Among the developments this month eggs by the end of the Cervix is the transformation of the gonads Mucus plug month; however, a male into either ovaries or testes. Tiny is not able to produce branches composed of smooth muscle sperm until puberty. are appearing in the lungs, in which Vagina minuscule air sacs will develop over the next few months and after birth. MONTH 5 I KEY DEVELOPMENTS

MOTHER

QUICKENING The first movement of the fetus felt by a pregnant woman is known as quickening. This movement, likened to a fluttering sensation, typically occurs in the fifth month and was an important stage in pregnancy FIRST MOVEMENT

CONCEPTION TO BIRTH TO CONCEPTION before ultrasound scanning was developed. Women who have not This usually happens been pregnant before often mistake quickening for wind. Those between weeks 18 and 24 of pregnancy. experiencing their second or later pregnancy often feel quickening Movements earlier than with their ﬁrst baby. This is partly because they know become stronger and more frequent what to expect and partly because the uterus is slightly thinner than as the fetus it was before, allowing minor movements to be felt more easily. continues to grow.

Surface SKIN PIGMENT CHANGES Darkly pigmented patches appear on the surface. During pregnancy, hormone changes can affect skin pigmentation, which often becomes noticeable in the ﬁfth month. The mother-to- Keratinocytes These cells contain a number of be may develop a thin, dark line of melanin pigment running from melanin granules determined by the the lower abdomen up to the navel and sometimes beyond. This activity of the melanocytes. is known as the linea nigra. A few women also develop irregular brown patches on the face. Known as chloasma, these patches can affect the upper cheeks, nose, forehead, or upper lip. Pigment Epidermis changes usually fade and disappear after the baby is born.

Melanocyte Melanosome Pigment-producing Melanin- Dermis cell that releases containing bodies melanosomes; this release melanin melanocyte is more granules, which active than the one to disperse within the right, so the skin the skin cells surface above it will (keratinocytes) generally be darker. above. MELANIN PRODUCTION Skin pigment changes are thought to result from increased CHLOASMA LINEA NIGRA stimulation of pigment cells (melanocytes), due to elevated Brown patches of pigmentation on The term linea nigra simply means “black levels of estrogen and progesterone. Because the pigment is the face are sometimes described as line” in Latin. It is thought to affect up to not uniformly taken up into all skin cells, patchiness can result. the “mask of pregnancy.” 75 percent of pregnant women.

Areola Secondary areola BREAST CHANGES The pigmented skin around A pale second areola may The breasts start to change during early pregnancy in the nipple is often relatively form; surrounding veins may narrow before pregnancy. also become more visible. response to rising levels of estrogen. By the fifth month, Nipple they are usually noticeably larger. As well as enlarging, and areola the breasts can become increasingly tender. The By the fifth month, the nipples and surrounding areolae darken and nipple and expand, and veins beneath the areola have become larger skin may look more pronounced. SIZE AND and darker. COLOR Small lubricating glands in the The breasts Montgomery’s tubercles areolae, known as Montgomery’s continue to Tiny glands within tubercles, are often visible as enlarge during the areola secrete a pregnancy in lubricating oil that small bumps. In the second preparation for attracts the baby to trimester, the breasts produce the nursing the baby. the nipple and may help The nipples and prevent infection. first stage of milk, colostrum, areolae become which can leak from the nipples. progressively darker. BEFORE PREGNANCY FIFTH MONTH 138 FETUS WEEKS 17–21

MID-PREGNANCY SCAN CONDITIONS A MID-PREGNANCY SCAN CAN DETECT By the ﬁfth month of pregnancy, the fetus’s organs and major bodily The mid-pregnancy scan is often referred to as a fetal anomaly scan because systems are well developed. The mid-pregnancy scan, usually carried out at it can detect major problems with the fetus or the mother. This table shows 20 weeks, checks whether development is progressing normally and detects that some developmental abnormalities are easier to identify than others.

major structural abnormalities. Important checks include making sure that NAME OF CONDITION DETECTION the fetus’s heart has four chambers and is beating normally, as well as RATE examining the abdomen to ensure that skin covers the internal organs. Anencephaly (absence of the top of the head) 99% Because the fetus moves constantly, it is not always possible to check everything on one scan, so the mother may need to return for further checks. Major limb abnormalities (missing or very short limbs) 90% Scan checks that skull Vertebrae examined to Right Right Left Left bones are complete check for spina biﬁda atrium ventricle ventricle atrium Spina biﬁda (open spinal cord) 90%

Major kidney problems (missing or abnormal kidneys) 85%

Cleft lip or palate (opening in the top lip or split 75% in the roof of the mouth)

Hydrocephalus (excess ﬂuid in the brain) 60%

Major heart problems (defects of chambers, 25% valves, or vessels)

PLACENTA LOCATION During the mid-pregnancy scan, the sonographer records whether the placenta is attached to the front or back wall of the uterus, at the top, CHECKING THE VERTEBRAE HEART DEVELOPMENT or whether it is low-lying (positioned close to the cervix). As the uterus Examination of the position and width The heart is usually the ﬁrst organ enlarges, a low-lying placenta usually rises up away from the cervix. of the vertebrae can identify a number of assessed to ensure that all four However, women with a low-lying placenta may be offered another scan developmental defects, including spina biﬁda. chambers have developed normally. at 32 weeks to ensure that its position will not affect a vaginal delivery.

Placenta attached to DETERMINING GENDER top of uterus Umbilical cord The gender of the fetus is fixed as soon as the sperm fertilizes the egg. By the 12th Uterus week of pregnancy, the fetal reproductive Lining of system is fairly well developed, but the uterus Placenta gender is not normally obvious until the Mucus plug often attaches mid-pregnancy scan at around 20 weeks. Cervix Within a female fetus, the ovaries already to side of uterus contain millions of eggs, and the vagina NORMAL NORMAL has started to develop as a hollow. Within a male fetus, the testes are anchored within the abdominal cavity but have not yet moved into the scrotum. The scrotal swelling forms a solid pouch at the base of the penis, which is often noticeable on the scan. The shape of the pelvic bones can help identify gender, too. Placenta covers Lower part cervical of placenta opening OLD WIVES’ TALES is close “Natural” methods of determining a baby’s gender to cervical include dangling a gold ring over the abdomen; if opening the ring swings in a circle, the woman is thought to LOW-LYING PLACENTA PREVIA be carrying a boy, and if the ring swings back and LOW-LYING PLACENTA forth, it is said to be a girl. Such methods are no A placenta that lies over or within 1 in (2.5 cm) of the cervix more accurate than tossing a coin, however. is known as placenta previa (see p.228). If it stays in this position, delivery must be performed by cesarean section. 139 THE FETUS AT 20 WEEKS By 20 weeks, a fetus looks completely human, with well-developed facial features, limbs, fingers, and toes, although the head is still disproportionately large at this stage. There is little subcutaneous fat on the face and limbs, and fine hair (lanugo) covers the body and limbs.

MONTH 5 I KEY DEVELOPMENTS

FETUS

CHANGING PROPORTIONS During the first trimester, the nervous system was undergoing a critical period of development. As a result, the brain and head grew quickly until they reached a size that comprised as much as half of the total length of the fetus’s body. In the fifth month, the fetal trunk and limbs enter a rapid growth spurt, so the head begins to look more adultlike in terms of proportion to the body. From now until birth, the head grows relatively little compared with the huge growth that the body experiences during this time. Measurement of the head and thigh bones can be used to accurately date the pregnancy and assess the age of the fetus, but this information is usually gleaned from the first ultrasound (11—14 weeks) or mid-pregnancy ultrasound (20 weeks).

1 ⁄4

1 ⁄2 PROPORTION OF TOTAL BODY HEIGHT BODY OF TOTAL PROPORTION 1 ⁄4

11 WEEKS 14 WEEKS 18 WEEKS AT BIRTH LONGER LIMBS CHANGING RATES OF GROWTH The arms are growing longer, as are the legs During the first trimester, the fetal head grows more quickly than and body. Conversely, the hands and fingers the body. Relative growth of the head then slows, so that by the still look large in proportion to the arms. fifth month, fetal proportions look more like those of an adult.

INCREASING MOVEMENT By the end of the fourth month the fetus’s limbs are HICCUPING fully formed, and its joints can move. It can now make the complete range of movements that a The fetus starts to hiccup in the middle of the second trimester; its full-term baby can make, such as yawning, sucking hiccups increase in intensity and its thumb, and practicing breathing movements. It frequency over the course of the waves its arms and legs frequently and is startled by pregnancy. They occur when its loud sounds. Although most movements are reflex diaphragm involuntarily contracts, actions, the continuing myelination of the nervous causing a sudden rush of air that closes the opening between the system (see facing page) causes some of these vocal cords (glottis). This reflex movements to become more coordinated. The fetus may have adapted to prevent milk starts to make deliberate movements, such as LIMB MOVEMENTS from entering the lungs of modern touching its lips and sucking its thumb. Although it This ultrasound scan shows a fetus flexing its muscles newborns during suckling, but by waving its arms and legs. It kicks and punches the this is not certain. can move its eyes, the eyelids remain fused and do uterus. These movements are felt by the mother and not open until the seventh month of pregnancy. often cause visible ripples on the abdomen. 142 WEEKS 17–21

MYELINATION By the ﬁfth month, some of the nerve axons linking the fetal limbs to the spinal cord are developing a fatty outer coating. This process is known as myelination—the nerves are electrically insulated so they can carry messages without affecting neighboring nerve cells. After myelination, messages pass more easily from the brain to the body (and from the body to the brain). As a result, fetal MYELIN AROUND movements become faster NERVE AXON and more coordinated rather An electron micrograph showing rings of myelin than being slow and jerky. sheath (blue) around a Myelination continues nerve axon, similar to insulation tape around throughout fetal life and an electric wire. early childhood. SENSORY STIMULI A 20-week-old fetus explores its left ear with one Axon Plasma hand and grasps its forearm in the other. The brain Schwann cell membrane stimulation received from exploring the environment cytoplasm surrounds axon contributes toward the fetus’s growing awareness.

INVAGINATION CLOSING UP AWARENESS OF 1 The ﬁrst stage of 2 As the axon myelination occurs sinks deep into the SURROUNDINGS when a nerve axon Schwann cell, a Exactly when a fetus becomes aware of its begins to sink into a double membrane Schwann cell. Each forms where the surroundings is unclear. The ﬁrst connections individual Schwann cell edges of the between brain cells (synapses) form during the wraps around a small Schwann cell meet. part of a single This is known as 12th week of pregnancy, but it is thought that true Schwann nerve-cell axon. a mesoaxon. awareness does not start until around the 20th cell nucleus week. Different types of awareness develop, such Layers of myelin as “quiet” awareness, when the fetus is awake but Longitudinal groove seems to rest, and “active” awareness, when it is awake and moves, often quite vigorously. The COILING COMPLETE fetus reacts to sounds within its mother’s body, 3 CONTINUES 4 MYELIN SHEATH As myelination Several layers of and noises in its external environment. As progresses, the membrane form a myelination and brain development progress, mesoaxon rotates myelin sheath around around the axon. It the axon, allowing the fetus’s awareness of its own body and its winds itself round messages to pass movements will increase. and round to form a down one axon tight wrapping that without affecting Mitochondria, encloses the axon. Fully other nerve activity. supplying cells myelinated with energy Nucleus axon Gap formed Vesicle, which between myelin releases sheath; known neurotransmitter Axon as node of Ranvier chemicals

Myelin sheath Synapse

Nerve cell Dendrite

STRUCTURE OF A NERVE CELL THE JUNCTION BETWEEN NERVE CELLS Schwann cells wrap around a nerve cell axon like beads This electron micrograph shows a synapse that forms a link on a string. Electrical messages jump between nodes Schwann cell between nerve cells (green). Electrical signals are carried to speed up nerve cell transmission. nucleus across through the action of neurotransmitters (red dots). 143 MONTH 6 I WEEKS 22–26 The sixth month brings the mother-to-be toward the end of the second trimester. The uterus and breasts are growing larger, and the amount of blood the heart pumps every minute increases. Most women gain around 18 oz (500 g) per week at this stage.

WEEK 22 WEEK 23 The bones within the fetus’s inner ear are beginning to harden, The fetal skin cells now start to accumulate a tough, protective and the coiled cochlear membrane is sufﬁciently developed to protein called keratin, the thickest layer of which is on the process low-frequency sounds. Over the coming weeks, the palms and soles of the feet. The skin is very wrinkled and is fetus starts to be aware of higher sound frequencies, too. The covered in greasy vernix and ﬁne lanugo hair, which protect nervous system is now developed enough for the fetus to start the fetus in its aquatic environment and may have an recognizing the sounds inside the uterus, such as the mother’s insulating effect. The nails start to appear at the base of the breathing, heart beat, stomach and intestinal rumbles, and her nail beds, and eyelids and eyebrows are developing. Small voice. It may be noticeable that the fetus becomes increasingly blood vessels appear in the lungs. The barrier between these responsive to sounds, and it will develop a startle reaction capillaries and the future air sacs is thinning to allow the to loud noises. As the nervous system develops, the fetus exchange of gases when the baby is born. Specialized lung becomes able to make much more sophisticated movements, lining cells (pneumocytes) are appearing. These will produce such as kicking and turning somersaults, and the mother a substance called surfactant, which reduces surface tension will be aware of this increased internal activity. so the small air sacs can expand more easily after birth.

OUTER EAR DEVELOPMENT AIR SAC DEVELOPMENT The ears develop low on the This light micrograph shows neck and move up as the jaw a pneumocyte in an air sac. bone enlarges. The ear is now Cells like these start to release almost in its ﬁnal position. surfactant in the coming weeks.

RESPONSE TO MUSIC Playing music to the fetus through headphones stretched over the abdomen may help stimulate brain development.

FUSED EYELIDS This photograph shows the fetus’s tightly fused eyelids. The act of touching its lips with its hands aids neural development.

144 123456789

WEEK 24 WEEK 26 Parts of the fetus’s brain involved in vision and hearing are The framework for the gray matter (cortex) of the fetus’s becoming more active. Memory is developing, and brain-wave brain is now in place. This is the location of nerve activity activity is now similar to that of a newborn infant. The mouth associated with consciousness, personality, and the ability to and lips show increased sensitivity, and the fetus hiccups and think. Around this time, fetal hand coordination dramatically yawns more often than before. Growth of the body and legs improves. The fetus can close its hands to make a fist and may has caught up with the head. Teeth buds for the adult set of spend a lot of time sucking its thumb. The brain surface is still teeth are appearing in the gums, and the nostrils are opening. looking smooth but as the cortex continues to mature, it will start to fold and form characteristic wrinkles. The testes in a male fetus now descend from the pelvis into the scrotum. REFLEX DEVELOPMENT The eyelids, which have remained fused since they formed This 3D ultrasound scan shows during the ninth week of development, also start to open. a fetus grasping the umbilical The fetus will blink regularly and may turn toward very cord. This is a reflex that occurs strong light that filters through the mother’s abdomen. if the cord touches the palm.

WEEK 25 The fetus is now growing rapidly as it accumulates muscle and fat. The mother’s uterus enlarges correspondingly, both upward and outward. This changes her center of gravity, and she must adapt her posture in order to maintain her balance. FISSURES AND RIDGES These changes can lead to problems such as backache. As Although still smooth, the brain’s the uterus grows, it also presses against the stomach and cortex will shortly fold into the ridges and furrows that provide diaphragm, which can reduce the ability to inhale deeply room for developing brain cells. and may increase symptoms of acid reﬂux and indigestion. The fetus’s brain is becoming increasingly complex. Nerve cells (neurons) are making new connections and laying down many nerve pathways. Some pathways receive sensory information from the body, while others send instructions to coordinate voluntary and involuntary movements.

NERVE CONNECTIONS DEVELOPING SENSES This micrograph shows fetal This 3D ultrasound image of brain cells; each cell body (red) a fetus taken at the end of has many dendrites (green) that the second trimester shows pass on impulses to other cells. that it can open its eyes.

145 CONCEPTION TO BIRTH

MOTHER AT 26 WEEKS MONTH 6 I WEEKS 22–26 The expanding uterus starts to cause a reduction MOTHER in lung volume, which MOTHER AND FETUS can cause breathlessness. 72 beats per minute Other discomforts, such as constipation, may also occur. 105/70 As the second trimester draws to a close, most women feel well Constipation 81⁄2 pints (4.8 l) and exhibit a healthy glow. However, stretchmarks may start to The growing uterus can exert appear during this month around the abdomen, and libido can pressure on the digestive system, leading to constipation. decrease. A vaginal ultrasound may be performed to measure 50% the length of the cervix and predict the risk of a premature Fundal height The height of the uterus above Levels of progesterone rise birth; this scan is often offered if the woman has suffered a late the pubic bone gives a good by 50 percent this month. miscarriage in a previous pregnancy. The development of the indication of the duration of Estrogen levels are also pregnancy. At 24 weeks, the steadily increasing. 1 fetus’s body systems has reached a point where it can now start height is around 9 /2 in (24 cm); using the energy and nutrients supplied via the placenta to lay the uterus now expands A cervical-length scan may be upward at a rate of around 3 performed to detect premature down some fat. This causes its weight to increase rapidly. Red /8 in (1 cm) per week. opening of the cervix. blood cells, which were previously only produced in the liver, Stretchmarks Most fetuses now settle into are now also being created in the marrow of the long bones. The expanding uterus causes a more regular cycle of rest If born prematurely toward the end of this month, a fetus has the abdominal wall to stretch, leading to the rapid thinning of interspersed with periods of a moderate chance of survival with intensive neonatal care. collagen and elastin ﬁbers in the vigorous movement. skin, resulting in stretchmarks.

12345678910111213141516171819202122 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 STATISTICS FETUS 150 beats per minute 14 in (36 cm) 26 oz (750 g) One-third The head, trunk, and legs now each comprise a third of the overall length of the fetus. 12% A fetus’s bones contain as little as 12 percent calcium compared to the 90 percent calcium in adult bones. 65% Premature babies born at 26 weeks have a 65 percent chance of survival, compared with only a 25 percent chance at 24 weeks. Chorionic villi Myometrium Maternal vein Endometrium

Maternal artery

Perimetrium Sound and vision The areas of the brain that process hearing and vision start to respond to sound and light. As a result, the fetus starts to Nail development recognize sounds such Skin begins to keratinize as its mother’s voice. and nails start to become visible.

Inner ear Increasing coordination The inner ear matures, As hand coordination improves, allowing sounds to be the fetus spends a lot of time sucking processed; bones in the its thumb and touching its face. The ear start to harden, fetus’s grasp reﬂex has developed, so leading to an improved that if a hand comes into contact sense of balance. with its foot or umbilical cord, it may grab hold.

Lung development Air sacs within the lungs Umbilical cord are developing, and the cells that will produce surfactant (a substance that allows the lungs to expand more easily) are forming.

Amniotic ﬂuid

Brown fat The fetus starts to lay down brown fat around the shoulders and upper back, which provides energy and Descending testes heat after birth. In a male fetus, the testes are descending into the scrotum, Changing proportions which is surrounded The relative size of the fetus by a liquid called is becoming smaller: the hydrocele. head, trunk, and legs each account for one-third of the total length. Hormone release The adrenal glands release steroid hormones, such as epinephrine, which prepares the fetus Mucus plug for stresses after birth. VIABILITY THRESHOLD The fetus doubles in size again this Amnion month. This is partly down to the Cervix Chorion accumulation of fat, which begins during this month. By 26 weeks, a baby born Vagina prematurely has a better than 50 percent chance of survival. MONTH 6 I KEY DEVELOPMENTS

MOTHER

STRETCHMARKS Epidermis Stretchmarks are creaselike The outer exposed layer of the skin— CHANGES TO LIBIDO ruptures in the skin. Also known known as the epidermis—remains intact over the surface of the stretch marks. DURING PREGNANCY as striae gravidarum, they are Sex drive can go up, down, or

CONCEPTION TO BIRTH TO CONCEPTION common in pregnancy. Their Dermis remain the same during pregnancy; appearance is partly related to Support tissues in the deeper layer of skin, the dermis, become stretched and despite the predictable hormone rapid weight gain and expansion thinned. This causes painless tears that changes that they experience, of the abdominal wall, and appear as stretchmarks on the surface. all women have different libidos. partly to the effects of the Psychological influences play a Subcutaneous fat large part, as does increased blood hormone progesterone. During pregnancy, increased amounts flow to the genital area, increased Stretchmarks are initially a of fat are laid down beneath the dermis, contributing to skin stretching. lubrication, and the fact that red–purple color and fade orgasm is often easier to achieve CAUSE OF STRIAE over time to a silver-gray. For Stretchmarks occur and more intense during pregnancy. unknown reasons, some women when collagen and Low sex drive may be linked to elastin fibers in the physical exhaustion, especially escape them altogether, even dermis are rapidly during the last three months. after multiple pregnancies. thinned and stretched. During this time, blood levels of Being overweight at the start the hormone prolactin—which of pregnancy increases the risk tends to lower libido—start AFFECTED AREAS of stretchmarks. Moisturizing to increase in preparation for Stretchmarks can lactation. Low sex drive is not massages and plenty of essential form anywhere, but are most common on inevitable because high levels of fatty acids in the diet may help the abdomen, hips, estrogen and progesterone help to reduce their formation. thighs, and breasts. reduce the effects of prolactin.

CERVICAL-LENGTH SCAN If there is a risk of premature delivery, a vaginal ultrasound scan may be carried out to measure cervical length. A lubricated ultrasound probe is gently inserted into the vagina to assess whether the cervix is becoming shorter and softer than normal. The cervical length is measured and the shape formed by the upper cervical canal (internal os) is also examined. A tight internal os, which forms a T-shape, is less likely to be associated with premature delivery. As the cervix shortens and the internal os beings to open, it will form a Y-shape, then a V-shape, and ﬁnally a U-shape. This funneling allows the amniotic membranes to bulge through and greatly increases the chance of premature delivery.

100 NORMAL LENGTH 80 This ultrasound scan shows the cervix during the ﬁfth month of 60 pregnancy. The scan shows a cervical RISK OF PREMATURE DELIVERY length of over 1 in (2.5 cm), which is 40 This graph shows the relationship normal. The risk of premature 20 between cervical length and the risk delivery in this pregnancy as a result of premature delivery during the 23rd of an incompetent cervix—a cervix 0 week of pregnancy. If cervical length that cannot retain a baby beyond a RISK OF PREMATURE DELIVERY (%) DELIVERY RISK OF PREMATURE 0 105 2015 2530 3540 45 50 55 60 65 70 3 falls below approximately /4 in ( 2 cm), certain stage—is low. The fetus is CERVICAL LENGTH (MM) the risk increases. LOCATION OF THE CERVIX not visible in this view. 148 FETUS WEEKS 22–26

RED-BLOOD-CELL PRODUCTION Red blood cells, which carry oxygen around the fetus’s body, are the most abundant of all cells in the body. During embryonic life, red blood cells are produced ﬁrst in the yolk sac, and from the third or fourth month of pregnancy by the developing liver and spleen. In the sixth month of pregnancy, the red bone marrow within the hollow spaces of the fetal long bones starts to take over this role. Substances produced in the fetal kidneys and the placenta regulate this process.

FETAL BONE MARROW This light micrograph shows a section of fetal bone marrow, containing many red blood cells. These cells have differentiated from embryonic stem cells (see p.99).

HEART RATE The fetal heart rate at this stage is around 140 –150 beats per minute. This varies in a predictable pattern during the day and night. As with the mother’s heart rate and blood FINGERS pressure, the lowest fetal heart DOPPLER THE DEVELOPMENT OF DIGITS This image of a six-month-old fetus rate and blood pressure occur The fetal heart beat shows how well the hands and fingers are is detected via the The fetal fingers and toes are fully developed by developed. The nail beds are laid down, and in the early hours of the mother’s abdomen the sixth month of pregnancy. The nail beds have the nail plates are starting to grow, and on morning (around 4 am); they with a Doppler the underside the fleshy pads are beginning fetal-heart-rate formed, and the nail plates start to appear. The to reveal their unique fingerprint patterns. rise again just before waking to monitor. The rate epidermal ridges that form creases on the palms reach a natural peak in mid- is displayed on the screen. of the hands and soles of the feet were laid morning. Although it is often down during early embryonic life; these are now said that higher heart rates FETAL HEART RATE becoming more visible as the fetal skin thickens occur in male fetuses, research The chart below shows the fetal and appears more opaque. These creases are involving 10,000 fetal heart rates heart rate at determined by the genes a fetus inherits. The shows this is not the case. Fetal different stages of pregnancy. It peaks fingerprints on the fleshy pads of the fingertips are heart rate does, however, vary early on and gently also becoming more obvious. Fingerprints are with the stage of pregnancy. fluctuates until birth. unique to each individual, and the whorls they 200 form are thought to reflect nutrition and placental 175 blood flow during the early stages of development. Some SPREADING TOES 150 This computer- research suggests that the generated image of RATE HEART 125 prints may help predict the a fetus’s legs at 22 weeks of pregnancy 100 0 4 8 12 16 28 32 40 individuals who will develop shows it can already 20 24 36 high blood pressure in later life. spread its toes. WEEKS OF PREGNANCY 149 MONTH 6 I KEY DEVELOPMENTS

FETUS

THE DEVELOPMENT OF HEARING Hearing is one of the ﬁrst senses to develop. The RECOGNIZING THE MOTHER’S VOICE inner, middle, and external ear develop separately, from three different parts of the embryo, but work A fetus recognizes its mother’s voice above all others. In part this is because her voice is heard most often, but it

CONCEPTION TO BIRTH BIRTH TO CONCEPTION together to detect sound. The complex outer ear is also because her body is a good conductor of sound shell (auricle) develops from six tiny bumps and vibration. The sound is conducted to the fetus (auricular hillocks) that are visible in a six-week- through the mother’s body tissues internally and also old embryo. These slowly enlarge and fuse to form externally through the air to reach the outer abdomen. Her voice is one of the ﬁrst things it learns to recognize the folded auricle. At ﬁrst, the ear forms on the as it becomes more aware of its surroundings. The lower neck. As the jaw bone develops, different powerful soothing parts of the fetal head grow at different rates, so the effect of the mother’s ears appear to move up until they are level with voice also provides the eyes. The external ear’s shape helps collect and comfort after birth. funnel sound waves into the auditory canal. They EFFECT ON HEART RATE pass through the eardrum (tympanic membrane) Studies carried out on and are transmitted across the three tiny bones EAR AT 22 WEEKS newborn babies have shown that their heart rate (ossicles) in the middle ear to reach the inner ear. By 22 weeks’ gestation the ear is almost completely formed. The auricle has risen up slows whenever they hear Here, sound vibrations are converted into nerve to its correct anatomical position, halfway their mother speaking. signals that are sent to the brain for processing. up the head and level with the eyes. The level of sound to which a fetus is accustomed

4 Cymba WHAT A FETUS 3 HEARS 3 concha 3 WHISPER 4 The uterus is full of noises, such as 5 Antitragus QUIET ROOM 2 the sound of the 5 2 4 mother’s heartbeat NOISE LEVEL INSIDE Helix 2 and the gurgling of THE UTERUS her intestines. This 1 6 1 6 5 means that the fetus BUSY STREET Tragus 1 is exposed to around 6 70 decibels of sound OF NOISE SOURCE LOUD MUSIC MONTH 1 MONTH 6 in the uterus— around the same JET ENGINE THE AURICULAR HILLOCKS sound level as an average conversation. During early embryonic life, the outer ear starts Concha Antihelix to form from six auricular hillocks. These enlarge 0 204060 80 100 120 140 160 and fuse and eventually form the folded auricle. NEWBORN LOUDNESS OF NOISE OR SOUND (DECIBELS)

REFLEX DEVELOPMENT Brain A baby is born with over 70 primitive reflexes 2 Each sensory nerve impulse is sent directly to the spinal cord Spinal cord that give protection in the early days of life. by sensory neurons (the brain is They are programmed into the nervous system not involved in reflex actions). during early development as nerve connections 3 The cell bodies 1 Stimulus are laid down. Some reflexes, such as the of motor neurons is applied. rooting and suckling reflexes, help with feeding. in the spinal cord initiate their own Others, such as the grasp reflex, are survival impulse back to 4 The two sets instincts that help stabilize the body. The grasp the muscles. of muscles involved in reflex develops at around 10 weeks’ gestation— grasping—one the fetus can close its in the forearm GRASP REFLEX and one in the This color enhanced fingers but only in an hand—are 3D ultrasound scan of incomplete way. By six MECHANICS OF THE GRASP REFLEX activated. a 24-week-old fetus A baby will grasp tightly if the palm is stroked with a KEY shows it playing with its months, a true but weak finger. A rapid sequence of nervous activity initiated SENSORY NERVE umbilical cord (purple). grasp reflex is evident. by the spinal cord is responsible for this action. MOTOR NERVE 150 WEEKS 22–26

PREMATURE BIRTH

A singleton baby born before 37 passes through the baby’s nose and an orange-yellow color. This is treated 100 weeks’ gestation is classed as preterm. down into the tiny stomach. Constant with a special “blue” light that If born prematurely, a fetus of 24 monitoring is vital because babies converts the pigment into a form that 90 weeks’ gestation has a moderate who are born early can develop can be excreted in the baby’s urine 80 chance of survival in a neonatal breathing problems and are also at and bowel motions. The length of intensive care unit. Resuscitation will increased risk of infection. Their body treatment depends on the baby’s 70 be needed, and the infant will receive systems, including their lungs and birth weight, age, and the level of 24-hour care from health professionals immune function, are not fully bilirubin in the blood. As soon as the 60 to ensure that he or she remains warm mature. At six months’ gestation, the baby’s condition allows, parents are 50 and receives the correct amount of baby will look tiny with wrinkled skin encouraged to actively help with oxygen and nourishment. Where and very little subcutaneous fat. The their baby’s care. Skin-to-skin contact 40 possible, the mother is encouraged to fetal liver has difﬁculty processing the is recommended, which provides 30 express her milk, which is then fed to red blood pigment—bilirubin—so comfort and helps the mother RATE SURVIVAL PERCENTAGE her baby through a feeding tube that jaundice will develop, making the skin bond with the baby. 20

LUNG UNDER- 10 DEVELOPMENT Many babies born 0 before 34 weeks’ 20 24 28 32 36 40 gestation have some GESTATION (WEEKS) degree of breathing difﬁculty. This is mainly SURVIVAL RATE due to the lack of The rate of survival increases the surfactant—a chemical longer the baby remains in the secreted by speciﬁc uterus. At 24 weeks, a baby has cells in the air sacs a 24 percent chance of survival. (alveoli) in the lungs By 28 weeks’ gestation, this rises that prevents these air to 86 percent. The youngest sacs from collapsing. LOCATION OF THE ALVEOLI premature baby to reach adulthood was born in Canada Collapsed Normal at 21 weeks and 5 days. alveolus ALVEOLI AT 24 WEEKS alveolus ALVEOLI AT BIRTH

Treating jaundice Ventilator Heart rate monitor LIFE SUPPORT AND MONITORING Blue light illuminates the A ventilator supplies varying amounts The baby’s heart is closely This image shows a 24-week-old baby in infant to treat the jaundice of oxygen to the lungs according to the monitored to ensure that it is a neonatal intensive care unit. The tubes that causes orange skin. A needs of the baby. Low positive pressure working properly. A typical heart and sensors monitor the infant’s well- shield protects the eyes. helps keep the tiny alveoli open. rate is 140–150 beats per minute. being and deliver oxygen, milk, and drugs.

151 Surfactant Released to help THE FORMATION OF THE air sacs expand and contract Alveolar RESPIRATORY SYSTEM type II cell Secretes The respiratory system undergoes regular stages of development, with surfactant; contains fine, a critical period occurring late in pregnancy. It does not perform its key hairlike structures on function—breathing—until after birth, and is filled with fluid until then. the surface

In the uterus, the fetus receives oxygen via the branches to form the left and right main bronchi. mother’s blood circulation in the placenta. After The right lung eventually develops three lobes, birth, the baby must immediately start to breathe while the left lung develops two, leaving extra SURFACTANT PRODUCTION on its own, both to obtain oxygen from the space for the heart. Development of the lungs Surfactant is a chemical produced by a speciﬁc type of cell in the air sacs of the surrounding air and to exhale waste carbon- is not usually complete until around 36 weeks’ lungs. It lowers surface tension so the air dioxide gas. The main airway in the lower gestation. Babies born prematurely may therefore sacs can expand and contract easily. This image shows surfactant (green) being

FORMATION OF THE RESPIRATORY SYSTEM OF THE RESPIRATORY FORMATION respiratory tract is the trachea, which starts to need treatment to help overcome breathing released by these alveolar cells. develop in the fifth week. In the same week, it difficulties during the first few days or weeks of life.

Trachea The main airway, THE UPPER RESPIRATORY SYSTEM this is also known as the The mouth, nose, and throat develop at the Rupturing oronasal windpipe. same time as the lower airways and lungs, but Nasal cavity membrane Olfactory bulb from a different part of the embryo. At ﬁve Brain Pharynx Olfactory nerves Developing weeks’ gestation, a thickening at the front of cartilage the head folds inward to form two nasal pits. Rings of cartilage help keep the larger This creates a ridge of tissue that becomes airways open. compressed by the developing upper jaw, forming the structure of the nose. The Primary

CONCEPTION TO BIRTH I THE BIRTH TO CONCEPTION mouth takes shape as the upper and lower palate jaw arches grow in from each side and fuse. Oral cavity Heart Oral cavity Nasal ORAL AND NASAL CAVITIES conchae The cavities of the nose and mouth are initially 6 WEEKS 12 WEEKS separated by the palate. As development progresses, Tongue Secondary the two airways meet at the back of the throat. palate

LUNG BUD STAGE Tertiary buds 4 WEEKS The respiratory Secondary bronchial system develops from a tiny lung bud that buds divide to form tertiary buds. branches off from the foregut. The base of Right main the bud eventually becomes the trachea and bronchus larynx. The lower end branches to form left This divides to and right bronchial buds, which will become form three the left and right main bronchi. These secondary continue branching to form secondary bronchial buds. and tertiary bronchial buds.

Foregut LUNGS AT 16 WEEKS Brain Epithelium This will soon differentiate LUNGS AT 7 WEEKS to form two types of cell. Lung bud Continual branching The bronchial buds LUNGS AT 6 WEEKS branch many times Connective over the next few weeks. tissue cell First branching Left main bronchus The lung bud branches This divides to form Capillary to form left and right two secondary These will gradually move LUNGS AT 5 WEEKS main bronchi. bronchial buds. closer to the alveoli.

PSEUDOGLANDULAR STAGE 5–7 WEEKS The developing respiratory system 16 WEEKS Yolk sac keeps dividing to form progressively more and increasingly smaller CANALICULAR STAGE tubes. After the secondary and tertiary bronchi have formed, The terminal bronchioles divide they will divide another 14 times to produce bronchioles by to form canal-like respiratory around the 24th week of gestation. These divisions determine bronchioles. These develop LUNG BUD FORMING IN the position, size, and shape of the lung lobes and lobules. At rounded protrusions at the ends A 4-WEEK-OLD FETUS Respiratory bronchiole Umbilical this early stage of development, the tiniest tubes are known as known as terminal sacs. Blood The furthest branch of the cord terminal bronchioles. vessels are developing nearby. respiratory tree at this point. 152 CONCEPTION TO BIRTH

Bronchioles These tiny terminals of the bronchi are made up of smooth muscle.

Bronchi These main branches consist of a framework of cartilage, joined by smooth muscle and ﬁbrous tissue.

Right main bronchus This is larger and angled more steeply than the left main bronchus.

LUNGS AT 36 WEEKS

Alveolar type II cell These cells start releasing LUNGS AT 28 WEEKS surfactant at 36 weeks, preventing the air sacs Left lung from collapsing when they are used after birth. This contains only Further division two lobes, or At this stage, the respiratory regions, to make bronchioles are dividing to room for the heart; form terminal sacs. the right lung has three lobes.

Elastin ﬁber These ﬁbers allow lung tissue to expand and contract with each breath, after the baby is born. Connective tissue cell Many more of these have Alveolar type I cell developed; they are now densely These cells become Capillary progressively thinner, packed. and form part of the blood–air barrier. 36 WEEKS Capillary ALVEOLAR STAGE 28 WEEKS These blood The terminal sacs now mature TERMINAL SAC STAGE vessels begin to The respiratory bronchioles to form thin-walled alveoli. The push into the thin walls of the alveoli and their Alveoli Alveolar capillary have divided to form primitive air developing air sac. membrane proximity to the capillaries allow Terminal branches sacs, called terminal sacs. These are now called alveoli; This lining is now continue to form during early Terminal sac Alveolar type II cell the transfer of oxygen and carbon these continue to so thin that gas childhood as the lungs grow larger. The furthest branch of These secretory cells will soon dioxide (a process called gas form before and exchange is Tiny blood vessels grow as close the respiratory tree is start to produce and release exchange) between the lungs after birth. possible. to the air sacs as possible. now called a terminal sac. surfactant. and the bloodstream after birth. 153 This 2D ultrasound shows a 33-week-old fetus in This MRI scan shows full-term twin fetuses. This 3D ultrasound shows a full-term fetus rubbing the uterus. Space is getting increasingly tight, and Twins are usually delivered earlier than single its eye. Its eyes have now opened and it is now its nose can be seen pressed against the placenta. babies, at around 37 weeks of pregnancy. sensitive to light, although it cannot yet focus.

TRIMESTER 3 MONTHS 7–9 I WEEKS 27–40

The third trimester of pregnancy is a time of maturation and rapid growth. By 40 weeks, a fetus’s organs will have developed to the point at which it is capable of independent life.

During the third trimester, the important fetal developments include roughly 15 in (38 cm) to 19 in (48 cm), and its weight rises from an 1 the laying down of fat, and the maturation of the body systems so average of 3 lb (1.4 kg) to 7 /2 lb (3.4 kg). The final 10 weeks are a that they can function fully on their own after birth. The respiratory remarkable period of growth, with the fetus gaining half of its final, system has to undergo a particularly dramatic transformation to full-term weight. By the end of this trimester, the fetus is fully formed enable breathing for the first time. To assist this, special cells in the and may have settled into a head-down position ready for birth. The lining of the air sacs (alveoli) produce a substance called surfactant; mother-to-be may suffer from back pain in the last three months, as this lowers surface tension, allowing the lungs to inflate easily. The postural changes lead to increased strain on muscles and ligaments. fetal brain continues to expand during these last three months, so the Fatigue can also be a problem, mainly due to the added weight of the head circumference increases from around 11 in (28 cm) to 15 in fetus. The breasts start to produce a creamy pre-milk called colostrum, (38 cm). At the same time, the fetus’s total body length increases from which will nourish the baby in the days after the birth.

TIMELINE

WEEKS 28–29 WEEK 30 WEEKS 32–33 A visit to the physician is usually scheduled. Braxton Hicks’ An prenatal visit is usually scheduled. From Blood is tested for anemia, while a glucose contractions usually now on, a checkup is offered at least once tolerance test may be offered to screen for increase in intensity a fortnight until the 40th week for a gestational diabetes. Women who have a from 30 weeks. singleton pregnancy. The average duration different blood group from their fetus will of pregnancy for quadruplets is 32 weeks. receive a dose of antibodies by their 30th

MOTHER week of pregnancy.

WEEK 27 WEEK 28 WEW EK 29 WEEK 30 WEEK 31 WEEK 32 WWEEK 33 MONTH 7 MONTH 8 WEEK 27 WEEK 28 WEEK 29 WEEK 30 WEEK 31 WEEKS 32–33 The eyelids open Small differences Three of the six The majority of The skin becomes The stomach ﬁlls every and sensitivity to are now visible layers of the cerebral blood cells are thicker and less 40 minutes, then empties. light develops. between the cortex have formed. now made by bone translucent. The eyebrows growth rates of Electrical activity marrow, although The pituitary gland The fetal intestines are now FETUS and eyelashes have male and female is registered in the the liver and spleen releases insulin and mature enough to digest milk grown considerably. fetuses. cerebral cortex. do continue to growth hormone. and absorb nutrients. make them.

154 At 40 weeks, the organs have matured and the eyelashes, eyebrows, and ﬁngernails are all in place. The fetus is now capable of life outside the uterus.

WEEK 34 WEEK 36 WEEKS 37–38 WEEK 39 WEEK 40 A visit to the physician is Tests may be offered to Examination of the mother’s abdomen shows The breasts are A prenatal visit is scheduled usually arranged for this check placental function, whether the fetus is in a head-down position. producing colostrum and if the baby has not already week to discuss the birth fetal growth, heart rate, If in a breech position, there is still time for the preparing for lactation. been delivered. If birth has plan and to receive and general well-being. fetus to turn by itself. The optimal time for not occurred by 42 weeks, vitamin K injections if the birth of twins is considered to be 37 weeks. labor is induced. required.

WEEK 34 WEEK 35 WEW EK 36 WEEK 37 WEEK 38 WEEK 39 WEEK 40 MONTH 9 WEEK 34 WEEK 35 WEEKS 36–37 WEEK 38 WEEKS 39–40 The suckling reflex The lungs now Most of the lanugo hair has been The fingernails now The liver is now mature enough to develops. consistently produce shed and replaced by fine vellus hair. reach the ends of take over all the metabolic functions surfactant, allowing Ossification is occurring in the the fingers. performed by the placenta. the alveoli to expand humerus, femur, and tibia. The eyes can move In male fetuses, the testes and collapse more Urine is now more concentrated but cannot focus. have usually descended into easily when breathing the scrotum by now. air after birth. due to the developing kidneys.

155 MONTH 7 I WEEKS 27–30 The mother-to-be now enters the third trimester. If the fetus is born prematurely, it is now capable of independent life and has a good chance of surviving with special care. Most development now focuses on the maturing of the brain, lungs, and digestive system.

WEEK 27 WEEK 28 From now on, natural differences in the growth rate between Despite massive fetal growth, there is still plenty of space male and female fetuses cause boys to be slightly bigger in the uterus, and the fetus may turn somersaults, spending and heavier at birth than girls. This difference is not usually some time in a head-down position and some time with its noticeable to the mother while the baby is still in the womb. head upright. As a result of all this exercise, the mother-to-be The fetus is now regularly swallowing, yawning, and making may feel kicks in several different parts of her abdomen. Skin practice-breathing movements. It starts to develop a regular creases are becoming visible on the fetal hands, which have pattern of resting and sleeping that alternates with periods taken on a chubby appearance, and the minute ﬁngernails are of wakefulness and activity. The protective layer of grease perfectly formed. Within the upper and lower gums, the teeth (vernix) covering the skin thickens. This coincides with the buds have now formed separate layers of enamel and dentine. kidneys maturing. They start to produce small quantities of During a prenatal visit, hemoglobin levels in the mother's urine that pass into the amniotic ﬂuid, and the vernix protects blood will be checked to detect signs of anemia. A glucose the fetus's delicate skin from irritation. The eyebrows and tolerance test may also be carried out in order to check for eyelashes are growing, and scalp hair is growing longer. maternal gestational diabetes.

STRETCHING FACE MUSCLES GLUCOSE TEST This 3D ultrasound image of a Urinalysis sticks make it easy fetus at the beginning of the for healthcare professionals to third trimester shows its mouth screen urine for glucose, hidden stretched wide open in a yawn. blood, protein, and infection.

TOOTH FORMATION Distinct layers now appear in each tooth bud: an outer layer of enamel (white), dentin (cream), and pulp (red).

UPSIDE-DOWN POSITION This MRI shows that the uterus’s shape helps the fetus into a head-down position, but its position may change frequently.

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WEEK 29 WEEK 30 The surface of the fetus's brain is becoming increasingly The fetus is now beginning to look increasingly rounded, folded to expand its surface area in order to accommodate plump, and well-nourished, and over the final 10 weeks the many millions of nerve cells that are being formed. of pregnancy, it will double its weight. The fetus now has More nerves are gaining the fatty myelin sheath that a regular sleep–wake pattern and spends approximately helps insulate them from one another; this speeds up the half the time resting quietly. Women with a Rhesus-negative development of the fetus's movements. The amniotic sac, blood group will receive a injection of anti-D antibodies by which envelops the fetus, and the amniotic fluid it contains the 30th week of pregnancy; another dose is given shortly are now fully developed. The two layers of the amniotic sac— after the birth. This helps neutralize an immune response the inner amnion and the outer chorion—slide over one if the mother is carrying a fetus with a Rhesus-positive blood another to reduce friction as the fetus twists and turns in the group. It will reduce the chances of the mother producing womb. Even up to the final weeks of pregnancy, when the her own anti-D antibodies, which might cause problems if fetus has reached its maximum size, the amniotic sac remains she becomes pregnant with another Rhesus-positive fetus amazingly flexible and continues to stretch as the fetus grows. at some time in the future.

MYELIN SHEATH This electron micrograph shows the axon (center ring) of a nerve cell surrounded by concentric rings of myelin sheath (blue).

RHESUS-NEGATIVE BLOOD This woman is having her blood tested for anti-Rhesus antibodies, to avert problems in future pregnancies.

PERSISTENT BACKACHE The enlarging uterus changes the center of gravity and posture, which often leads to back strain and discomfort.

RAPID WEIGHT GAIN This 3D ultrasound image of a fetus during the third trimester of pregnancy shows its face has started to ﬁll out with fat.

157 CONCEPTION TO BIRTH

MOTHER AT 30 WEEKS MONTH 7 I WEEKS 27–30 The mother may start to suffer from backache as her MOTHER changing center of gravity MOTHER AND FETUS puts increasing strain on 72 beats per minute ligaments and muscles. She may also notice that the 106/70 The seventh month marks the start of the final trimester. In the fetus startles when hearing a loud noise. 9 pints (5.1l) first week of this month, the fetus’s eyelids usually separate and it begins to blink. Nutrients are increasingly diverted toward Minor contractions producing muscle and fat, and so the fetus continues the Minor contractions stemming from the fundus 40% growth spurt that started at the end of the previous month. of the uterus become more The tidal volume—the The fetus’s kidneys now produce urine in increasing quantities, noticeable toward the end amount of air inhaled and of the month. which is frequently released into the amniotic fluid. Its skin is exhaled in one breathing motion—has risen 40 percent covered in a protective layer of grease called vernix that, among Changing center since pregnancy began. other functions, helps the fetus descend through the birth canal of gravity As the uterus enlarges, the Braxton Hicks’ contractions when the time is right. The mother may undergo a glucose mother’s center of gravity begin to increase in intensity tolerance test to check for maternal gestational diabetes. If moves forward, and her posture changes. This from the 30th week. blood tests in early pregnancy revealed the mother to have accentuates the lumbar a Rhesus-negative blood group, she will usually receive her curve in the lower back The mother has typically and can lead to backache. gained 15 lb (7 kg) by the first dose of anti-D antibodies in the middle of this month. end of the seventh month.

1234567891011121314151617181920212223242526 27 28 29 30 31 32 33 34 35 36 37 38 39 40 STATISTICS FETUS 150 beats per minute 151⁄2 in (40 cm) 23⁄4 lb (1.3 kg) 33% In one-third of pregnancies, the fetus lies in a breech (bottom-down) position in the 30th week, but only 3 percent of fetuses remain in this position until birth. 10% Twins put on the same amount of weight as single fetuses until the 28th week, after which there is a 10 percent reduction in their relative rate of growth.

In the 30th week, the fetus only spends a tenth of its time awake. Chorionic villi Transfer of antibodies Immunities are now efﬁciently transported Maternal vein from the mother to the fetus.

Maternal artery Perimetrium

Myometrium

Umbilical cord

Amniotic ﬂuid Endometrium

Fat accumulation The fetus continues to gain weight rapidly; the majority of this is fat. Covering of vernix The fetus’s body is now covered in a greasy, protective substance Tooth development called vernix. The milk teeth have formed distinct layers of enamel and dentin surrounding the inner dental pulp. Amnion

Chorion

Eyelids open The eyelids are no longer fused together; sensitivity to light begins to develop. Neural connections Connections between Hair growth the thalamus and cortex Eyebrows and eyelashes develop, giving the fetus grow considerably during this month; hair on the increasing awareness BRAIN AND LUNG DEVELOPMENTS of its body. fetus’s head also begins to lengthen. The nervous and respiratory systems are entering important periods of Mucus plug development. Neural connections between the thalamus and cerebral cortex increase the fetus’s awareness Vagina Cervix of its body. Primitive air sacs are now beginning to form in the lungs. MONTH 7 I KEY DEVELOPMENTS

MOTHER

THE CHANGING CENTER OF GRAVITY FLEXIBLE VERTEBRAE PRENATAL CLASSES The vertebral bones interlock During the third trimester, the increasing volume and in a series of sliding joints to Prenatal classes provide important information weight of the uterus moves the pregnant woman’s center produce four gentle curves that helps a pregnant woman, and her partner, that provide strength, of gravity forward. To counteract this and maintain stability, ﬂexibility, and stability. These prepare for childbirth emotionally and physically.

CONCEPTION TO BIRTH TO CONCEPTION it is natural for the mother-to-be to lean backward. curves are known as the Classes usually cover what happens to the baby However, this causes the long muscles running down the cervical, thoracic, lumbar, and and the mother during birth, positions to adopt sacral curves. As the center spine to work harder to pull the shoulders back and lift the of gravity changes during during labor, and possible interventions, such as abdomen. As the shoulders pull back, the head naturally pregnancy, it is natural to cesarean section, delivery by vacuum extraction, lean back, placing more strain moves forward. These changes in posture can lead to back, on the ﬁve vertebrae that and delivery by forceps. Breathing exercises and shoulder, and neck aches. make up the lumbar curve. relaxation techniques are taught, and the different methods of pain relief are discussed.

BIRTH EDUCATION Prenatal classes are a relaxed way of preparing for labor, birth, and the first few months after Flexible lumbar the birth. vertebrae allow women to lean back and Lumbar maintain PRENATAL APPOINTMENTS vertebrae balance Regular tests in the third trimester include checking the mother’s blood pressure, the height of the uterus, and the position of the fetus. Urine is tested Center Center of for protein, glucose, the presence of blood, and of gravity gravity moves other signs of infection. Blood is checked for signs forward in late pregnancy due of anemia, and a glucose tolerance test may be to weight gain performed. If the mother is Rhesus negative and her partner is Rhesus positive (see p.230), anti- VERTEBRAL COLUMN VERTEBRAL COLUMN IN LEANING BACK ADJUSTS BEFORE PREGNANCY LATE PREGNANCY THE CENTER OF GRAVITY Rhesus antibody levels are checked regularly. Injections may be BACKACHE DURING PREGNANCY needed if the antibody level is too high. The change in posture during late pregnancy Inflammation of places extra strain on the muscles, ligaments, sacroiliac joint and joints in the lower back, causing pain. Other Causes persistent pain in CHECKING GLUCOSE LEVELS middle and lower back factors that increase back pain include reduced If glucose is found in the levels of exercise, diminishing muscle tone in the mother-to-be’s urine, a glucose tolerance test will be needed to core abdominal region, and the increased check for gestational diabetes. secretion of the hormone relaxin, which softens ligaments as delivery approaches, often leading to inflammation and pain in many joints in the THIRD TRIMESTER HOSPITAL APPOINTMENTS body. Back problems can also occur during WEEK 28 Hospital visit to test for gestational diabetes and anemia; pregnancy through lifting heavy objects with the injection may be given if Rhesus incompatible back hunched and without bending the knees. WEEK 34 Hospital visit to discuss birth plan; second injection may be given if blood is Rhesus incompatible LOCALIZED PAIN AREAS Pressure on In addition to discomfort from strained vertebrae WEEK 41 Hospital visit organized to discuss possible joints and ligaments, surrounding Causes pain Pubic joint strain induction of labor muscles may go into spasm, causing around coccyx Leads to pain in WEEK 41 Hospital visit to maternity day care unit; pain and tenderness over a larger area. front of pelvis + 3 days ultrasound performed to assess fetal well-being

160 FETUS WEEKS 27–30

THE DESCENT OF THE TESTES Testis Testis has started Subserous to descend The testes develop within the abdominal cavity of a Peritoneum fascia Transversalis Inguinal canal fascia developing male embryo, near the kidneys. They become Transversus attached to a ligament on each side, known as the abdominis muscle gubernaculum. Between the 28th and 35th weeks of Internal oblique pregnancy, each gubernaculum becomes shorter and muscle External Gubernaculum thicker. This acts as a guide, pulling the testes downward Gubernaculum MONTH 2 oblique anchors testis MONTH 3 through the inguinal canal and into the scrotum. Moving anchors testis muscle to groin outside the abdomen into the scrotum helps keep the near groin testes cool, which improves the quality of sperm when it is produced from puberty onward. Testis has begun its descent Scrotal through inguinal Scrotum swelling MONTH 8 canal MONTH 9

THE FINAL DESCENT HOW AND WHERE THE TESTES MOVE Gubernaculum Testis has now The testes should move into The testes descend from the abdominal cavity starts to descended into the scrotum before birth. In through the inguinal canal, a narrow tunnel that disintegrate the scrotum 1 percent of full-term and 10 passes over the pelvic bone and into the scrotum. after testis has percent of premature boys, one Once the testes are in position in the scrotum, descended testis remains undescended. the gubernaculum withers away on either side.

Suspensory Neural layer THE DEVELOPMENT OF THE EYE ligament of lens of retina The eyelids, which have been fused since the Iris Inner layer Cone cell end of the ﬁrst trimester, begin to separate at the of retina Cornea Detects ﬁne detail beginning of the seventh month, allowing the fetus Hyaloid and color artery to open its eyes and start to blink. All the layers of Eyelids fused Horizonatal cell the retina at the back of each eye have now Regulates input from developed, including the light-sensitive cells known rods and cones Eyelid as rods and cones. A small amount of light passes through the mother’s abdominal wall to stimulate Lens the fetal rods, which detect shades of black, gray, and white in the dim conditions. The fetus can 17 WEEKS recognize the difference between light and dark, Scleral venous sinus day and night, and see the outline of its hands, Iris Ganglion cell Transmits knees, and umbilical information cord. Color vision, Cornea from retina to several regions which arises as a Suspensory of the brain result of stimulation ligament of the cone cells, is not of lens thought to develop Choroid until after birth. Ciliary body Optic nerve Amacrine cell Rod cell Exact function is Responsible Hyaloid artery unknown, but for vision in EYES START TO OPEN 26 WEEKS probably similar to dim light This 3D ultrasound of a fetus horizontal cells in the seventh month shows ANATOMY OF THE EYE AT 17 AND 26 WEEKS the eyelids beginning to A number of developments take place between 17 and Bipolar cell separate. Sensitivity to light 26 weeks. The lens becomes less spherical and more Transfers information develops, and the fetus will ovoid, the eyelids separate, and the ciliary body forms, from ganglion cells to turn toward bright light. which allows the lens to move and change shape. rods and cones 161 MONTH 7 I KEY DEVELOPMENTS

FETUS

Oral Dental Expanding Disintegrating THE FORMATION OF TEETH Developing epithelium lamina dental papilla dental lamina The ﬁrst set of 20 milk (or deciduous) teeth start permanent tooth bud developing around eight weeks into pregnancy. Permanent Buds form from the band of tissue (dental lamina) tooth bud

CONCEPTION TO BIRTH TO CONCEPTION that runs along both jaws. The lamina guides the buds into position and disintegrates. The tooth Enamel organ buds then fold inward to form a bell-shaped Dental structure. Cells of the inner enamel epithelium papilla deposit hard enamel on the developing tooth’s Dental sac surface, while dental papilla underneath produces the softer dentin and pulp. In the seventh month, EARLY BELL STAGE LATE BELL STAGE enamel and dentin have formed separate layers. 1 By 10 weeks, the milk teeth start 2 By 14 weeks, the dental lamina to form within a dental sac. The connecting the tooth to the gum The permanent tooth buds form during the third permanent tooth bud begins to surface is no longer needed and month, but then develop beside it. starts to break down. lie dormant until Inner enamel epithelium around six Enamel Enamel Dentin years of age. Dentin

Periodontal Enamel Permanent ligaments tooth bud Dentin Bone Alveolar bone Dental pulp Developing Dental pulp permanent tooth bud Epithelial PROTECTIVE LAYER root sheath A thick layer of hard ENAMEL AND DENTIN EARLY ERUPTION STAGE enamel (red) protects 3 By the seventh month of 4 The tooth bulges onto the surface the softer dentin pregnancy, the milk teeth have of the gum until the crown breaks through. (pink) and pulp distinct layers of enamel and dentin Eruption of the milk teeth occurs between (yellow) beneath. surrounding the inner dental pulp. six months and two years after birth.

MUSCLE AND FAT ACCUMULATION VERNIX The length of the fetus increases steadily throughout Vernix caseosa is a white, greasy substance that forms a pregnancy. This allows the age of the fetus to be assessed coating on the fetus’s skin. It starts to appear around the 20th with relative accuracy using measurements taken during week of gestation, and by the seventh month it covers most ultrasound scans. The rate at which the fetus gains weight of the fetus’s body. Made up of fetal skin oil (sebum), skin increases slowly at first, but starts to accelerate in the cells, and lanugo (fine hair), vernix helps moisturize and seventh month. Muscle and fat are being laid down, and protect the skin from constant exposure to amniotic fluid, GROWTH SURGE the fetus starts a growth which, due to the development of the kidneys in the third Fetal length increases steadily spurt, doubling in weight trimester, contains more throughout pregnancy, but most weight gain occurs from the seventh between week 30 and week concentrated fetal urine. month onward. 40 of pregnancy. Vernix also helps

3,000 350 KEY lubricate the baby as it FETAL 2,500 300 LENGTH passes down the birth 250 2,000 FETAL canal during labor. 200 WEIGHT 1,500 150 1,000 100 PROTECTIVE COVERING 500 50 (MM) LENGTH FETAL A thick, slippery layer of vernix FETAL WEIGHT (GRAMS) FETAL 0 may still be present at birth. 10 222018161412 24 302826 32 The term vernix caseosa means AGE (WEEKS) “cheesy varnish” in Latin. 162 WEEKS 27–30

THE BIRTH OF CONSCIOUSNESS Consciousness is roughly deﬁned as sensory awareness of the body, awareness of the self, and awareness of the world. The fetus starts to develop one of these constituent parts—awareness of the body—by the seventh month, because it can now react to smell, touch, and sound. The other constituent parts only start to develop after birth. In the seventh month, the number of connections (synapses) between brain cells is increasing, and the nerve activity associated with consciousness, personality, and the ability to think are developing. Many different nerve pathways are being laid down between the brain and the body. Some pathways receive sensory information from the body, while others send instructions that help coordinate voluntary and involuntary movements. Much of the information coming into the brain passes through the thalamus, where it is processed and sent on to the correct part of the cerebral cortex for analysis. The thalamus is also involved in the regulation of consciousness, alertness, and awareness.

Neural connections Cerebral forming between cortex thalamus and cerebral cortex

Thalamus

THE DEVELOPING NERVOUS SYSTEM This 3D MRI scan shows the central nervous system (the brain DEVELOPING NEURAL NETWORKS and spinal cord) during the 27th This illustration shows the fetal brain at 28 weeks. At this time, week of development. Ridges connections form between the thalamus (green area) and the (gyri) and ﬁssures (sulci) have cerebral cortex. One of the roles of the thalamus is to process started to appear faintly on the sensory signals. The connections that are forming allow these signals surface of the cerebral cortex. to be relayed from the thalamus to the relevant part of the cortex. 163 MONTH 8 I WEEKS 31–35 During the eighth month of pregnancy, the fetus gains weight at a dramatic rate. All the body systems are maturing in readiness for delivery in the near future. The mother-to-be may develop an urge to clean, tidy, and “ready the nest,” but it is important to ﬁnd time for rest and relaxation.

WEEK 31 WEEK 32 The fetus’s skeleton has now grown almost to its birth size. The air sacs (alveoli) in the fetus’s lungs are now multiplying Because the fetus will still gain a lot of weight, it looks rather rapidly. Although they contain fluid, the fetus has been long and thin at this stage. The skin is thickening and now making practice-breathing movements for the last five months. looks pink rather than red because a layer of fat has been The movements have been short bursts lasting no more than building up beneath the surface. The fetus is quite flexible, and 10 seconds. Over the next few weeks, the breathing pattern there is still room in the amniotic sac for it to bring its feet up becomes more regular and rhythmic as the fetus builds up toward its head and even to put its toes in its mouth. Due to toward the 40 breaths per minute it will need to make after the cramped conditions in the uterus, the growth of multiple birth. The mother-to-be may feel increasingly tired during the babies now starts to slow down compared with that of last trimester of pregnancy. As well as carrying the additional singletons, and they will also tend to be born before the due weight of the fetus, enlarged uterus, and amniotic fluid, her date. Even at this stage, some fetuses are already in the heart has to work harder to pump extra blood around her head-down position in preparation for birth, but others will body. Lying down for regular rests during the day increases not turn until much closer to the end of pregnancy. blood flow to the fetus and helps both mother and baby.

TWIN GROWTH INCREASING BLOOD FLOW This MRI scan shows tightly Lying down to rest during the packed twins in the eighth day has the added beneﬁt of month. The lone placenta (lower helping boost the blood ﬂow right) suggests they are identical. through the placenta.

SENSORY AWARENESS This 3D ultrasound scan shows a fetus touching its face. It is now more aware of sensations and spends time exploring its body.

RANGE OF MOVEMENT A fetus can bring its feet up to its head with ease. The toes can spread and brace the foot against the uterine wall.

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WEEK 33 WEEK 34 The fetus hears many sounds from its environment. It The fetus starts to spend less time asleep and is awake and is aware of its mother’s heartbeat, intestinal rumbles, and active much longer, so that by the time it is born, it is awake breathing, as well as the whoosh of blood moving through for around eight hours out of every twenty-four. The fetus is the placenta and umbilical cord. As the brain matures, becoming much more aware of itself and its immediate world, the fetus remembers and adapts to these sounds and will and will often touch its face, grip the umbilical cord, and suck recognize its own mother’s voice better than anyone else’s. a thumb. Its sucking reﬂex has become quite strong, and if it Loud noises may make the fetus startle, and the mother is born between now and full term, it should be able to suckle may feel the reaction as a kick. She may start to notice and feed quite easily. As the fetus puts on weight and grows regular tightening of the uterus, known as Braxton Hicks’ larger, there is less room to move around within the uterus. contractions. These practice contractions help strengthen As fetal movements are also becoming more coordinated, uterine muscles in preparation for labor. The fetal intestines the mother may feel them as joined up slithers rather than have now matured to such an extent that they are capable individual kicks. It may feel to the mother as if the fetus is of fully digesting and absorbing the nutrients from milk. moving more now than previously.

UMBILICAL BLOOD VESSEL COMPLEX OUTER EAR This electron micrograph The fully formed outer ear in shows a blood vessel (red) in the this ultrasound scan is able to umbilical cord, which keeps the collect and funnel sound. Loud fetus supplied with nutrients. noises will startle the fetus.

WEEK 35 The fetal lungs now start to produce surfactant, a substance that allows the air sacs to open more easily. If the fetus were born now, it would be capable of breathing unaided but it will beneﬁt from a few more weeks in the uterus to put on weight and mature fully. The hormone relaxin—produced throughout pregnancy—now has an extra function in helping relax the pubic ligaments and soften the cervix for delivery.

RELEASING SURFACTANT This artwork shows alveolar cells in the air sacs of the lung. The ﬁngerlike projections release the vital chemical, surfactant.

165 CONCEPTION TO BIRTH

MOTHER AT 35 WEEKS MONTH 8 I WEEKS 31–35 A number of changes occur in the mother’s body, including MOTHER rising hormone levels and MOTHER AND FETUS the increasing regularity of 74 beats per minute Braxton Hicks’ contractions, both of which begin to 109/73 prepare the body for labor. The continuing accumulation of fat stores this month proves 10 pints (5.5 l) to be vital because it provides a baby with energy in the first few days after birth, before milk is produced. The fetus now Continuing contractions Braxton Hicks’ contractions starts to spend less time asleep and more time awake. Practice become stronger and more frequent during this month. 1.5 pints breathing occurs as the chest wall moves consistently, which The amount of amniotic prepares the lungs and respiratory control centers in the brain Additional weight fluid in the uterus has now for the baby’s first breath after birth. The mother’s levels of the The increasing weight of reached 1.5 pints (800 ml). the fetus, compounded by It starts to decrease in the hormone relaxin increase, loosening the pubic ligaments and various hormonal changes, ninth month. softening the cervix in readiness for birth. The enlarging uterus can make the mother increasingly tired. presses down on the pelvic floor, compressing the bladder and Increasing production increasing the mother’s urge to urinate. Most expectant mothers of relaxin Over 40% now start to feel increasingly tired. Prenatal visits usually The hormone relaxin is The mother’s total blood produced in increasing volume is now over increase in frequency to monitor both mother and fetus as quantities, which softens 40 percent greater than it the joints in preparation was prior to pregnancy. pregnancy approaches its final stage. for the baby’s descent through the birth canal.

1234567891011121314151617181920212223242526 27 28 29 30 31 32 33 34 35 36 37 38 39 40 STATISTICS FETUS 144 beats per minute 18 in (46 cm) 51⁄4 lb (2.4 kg) 0.88 pints The fetus swallows around 0.88 pints (500 ml) of amniotic ﬂuid a day. Most of this is urinated back Endometrium Myometrium Perimetrium into the amniotic ﬂuid.

In a male fetus, the testes Chorionic villi are starting the final descent Amniotic fluid through the inguinal canal and into the scrotum. Maternal artery Specific cells within the air sacs (alveoli) in the lungs start to release surfactant Maternal vein in the 35th week. This allows the air sacs to inflate and deflate without collapsing, which is vital when the baby starts breathing after birth. Umbilical cord

Digestive system developments The gut has now developed to the point that food can be digested.

Final lung developments Two major changes occur this month: surfactant is produced from the 35th week onward; and the development of the blood-air barrier means that gas exchange is now possible after birth.

Urine production The volume of the bladder is now approximately 1 /3 ﬂ oz (10 ml).

Changing color The skin becomes thicker and less translucent; in white -skinned babies, it Chorion also changes color, Nail growth from red to pink. The ﬁngernails now reach the tips of the ﬁngers. Amnion

Preparation for feeding The suckling reﬂex develops, allowing the baby to feed after birth.

LATE DEVELOPMENTS Skull bones The skull bones are Among the most signiﬁcant complete but remain developments this month is the able to mold to the production of surfactant, which Mucus shape of the birth plays a vital role in breathing. Also, plug canal, protecting the the digestive system is now capable brain during birth. of breaking down food. If the baby Vagina Cervix is born during this month, it has a very good chance of survival. MONTH 8 I KEY DEVELOPMENTS

MOTHER

BRAXTON HICKS’ CONTRACTIONS RELAXIN IN LATE PREGNANCY The uterus contracts regularly throughout pregnancy. Relaxin is a hormone that softens the pelvic Breast Known as Braxton Hicks’ contractions, these “practice” joints and ligaments—as well as other ligaments contractions become more noticeable from the eighth in the body—in preparation for childbirth. Placenta and

CONCEPTION TO BIRTH BIRTH TO CONCEPTION month onward and they are sometimes mistaken Although these changes can lead to the chorion for labor. These contractions are felt as tightening backache and pelvic pain that are often (membrane between sensations and may last for a minute or more. experienced in late pregnancy, relaxin also mother and However, they do not produce the cervical dilation makes the bones of the mother’s pelvis more fetus) that occurs during labor. They squeeze the fetus and ﬂexible, which allows the birth canal to widen are thought to be an enough for the fetal head to pass through. In UTERINE ACTIVITY IN PREGNANCY important stimulus addition, relaxin may aid in the development Decidua These charts show Braxton Hicks’ for its developing of blood vessels in the uterus (lining of the contractions appearing as regular WHERE RELAXIN pregnant increases in uterine pressure (measured senses, and to tone and placenta; it is also IS PRODUCED uterus) in millimeters of mercury). These the uterine muscle thought to relax the uterus, Relaxin is produced contractions become increasingly in the breasts, ovaries, Ovary intense in the eighth month, but are in preparation allowing it to stretch as placenta, chorion, still minor compared with “true” labor. for labor. pregnancy progresses. and decidua.

14 WEEKS’ GESTATION Sacroiliac joint 50 This joint is often the Ilium source of pelvic girdle pain

Iliac crest

(mm Hg) Sacrum PRESSURE PRESSURE 0 0 5 10 15 20 TIME (MINUTES)

24 WEEKS’ GESTATION 50 (mm Hg) PRESSURE PRESSURE 0 0 5 10 15 20 Coccyx Pelvic brim TIME (MINUTES)

30 WEEKS’ GESTATION 100 Pubis bone Obturator foramen (mm Hg) PRESSURE PRESSURE 0 PELVIC PAIN 0 5 10 15 20 The softening of pelvic joints can TIME (MINUTES) cause inflammation and pain during late pregnancy. Pelvic girdle pain is 36 WEEKS’ GESTATION Ischium Pubic symphysis 100 felt at the back of the pelvis, and This joint links the two halves symphysis pubis dysfunction of the pelvis; it is the source of affects the front of the pelvis. symphysis pubis dysfunction (mm Hg) PRESSURE PRESSURE 0 0 5 10 15 20 TIME (MINUTES) INCREASING FATIGUE 38 WEEKS’ GESTATION 100 A pregnant woman often feels increasingly tired toward the end of pregnancy. This is partly because of the extra weight she has to carry and partly because of the various (mm Hg) PRESSURE PRESSURE 0 hormonal changes that are taking place within her body. 0 5 10 15 20 Exceptional fatigue can also be TIME (MINUTES) a sign of iron deficiency (anemia). It is for this reason BENEFITS OF REST LATE FIRST STAGE OF LABOR Sitting or lying down 100 that prenatal clinics perform increases blood flow to blood tests to screen for the uterus and is therefore anemia at various stages beneficial to both mother (mm Hg) PRESSURE PRESSURE 0 of pregnancy. and fetus. 0 5 10 15 20 TIME (MINUTES) 168 FETUS WEEKS 31–35

RAPID GROWTH As the placenta matures, it approaches its peak efﬁciency, TWIN PREGNANCY allowing for maximum transfer of oxygen, glucose, and other vital nutrients to the fetus. As much as 70 percent of these When twins share a uterus they also share maternal resources, including nutrients and space. As a result nutrients are destined for the rapidly growing fetal brain. The of this competition, their growth now starts to slow fetal body is now almost fully developed, and it is able to divert compared with single babies (or “singletons”), and they MUSCLE FORMATION precious energy resources toward laying down stores of body This color-enhanced MRI tend to be born earlier. On average, a twin pregnancy fat. The fetus starts to look better nourished as the wrinkles scan of an 8-month-old lasts for 38 weeks, while a singleton pregnancy lasts fetus in the uterus shows around 40 weeks. As a result of being born earlier, in its skin begin to ﬁll out, and as it grows, the fetus is starting that the fetal musculature twins usually weigh less than single babies. to get cramped inside the uterus. (pink areas) is well formed. 40

10 PERCENTAGE OF BABIES BORN OF BABIES PERCENTAGE 0 20 2224 26 2830 32 34 36 38 40 42 LENGTH OF PREGNANCY (WEEKS)

10 PERCENTAGE OF BABIES BORN OF BABIES PERCENTAGE 0 < 1 , 0 0 01 , 0 0 0 – 1 , 5 0 0 – 2 , 0 0 0 – 2 , 5 0 0 – 3 , 0 0 0 – 3 , 5 0 0 – 4,000+ 1,499 1,999 2,499 2,999 3,499 3,999 BIRTH WEIGHT (GRAMS)

EARLIER AND LIGHTER KEY The top graph shows that twin babies are SINGLE BABIES usually born a couple of weeks earlier than singletons. The bottom graph shows that TWINS 1 twins are born around 2⁄2 lb (1 kg) lighter.

“PRACTICE” BREATHING The air sacs (alveoli) within the fetal lungs are almost fully formed, and the fetus now spends Red areas show around half its time “practice” breathing—so called amniotic fluid because the fetus is preparing to breathe oxygen, being expelled which will take place only after birth. During “practice” breathing, the amniotic fluid does not actually enter the fetus’s lungs, but the accompanying EARLY BREATHING This colored Doppler movements of the diaphragm ultrasound scan shows a fetus and chest wall are vital at about 17 weeks “practice” breathing amniotic fluid. The for stimulating normal lung red patches show fluid coming development. out of the fetus’s mouth. 169 MONTH 9 I WEEKS 36–40 The fetus is now fully formed and may already have settled in a head-down position ready for birth. During the last few weeks of pregnancy, the fetus lays down increasing amounts of fat as a reserve for the less protected life outside the uterus.

WEEK 36 WEEK 37 The estimated date of delivery is approaching, but only At 37 weeks, fetal development is considered complete, and 1 in 20 babies is born on the due date as calculated at a singleton fetus is classified as full-term. Around 1 in 10 is the beginning of pregnancy. A birth date that is up to born before this milestone and is recorded as premature two weeks earlier or two weeks later than calculated is still or “preterm”; the earlier it is born, the more complex and considered normal. The placenta is becoming less efficient, numerous the problems. The fetus’s body now has a good and monitoring is important to ensure that the fetus continues layer of fat and looks healthy and plump. It is ready to be to receive all the nutrition it needs. A number of specialized born. Most of the lanugo hair that covered it during early tests may be offered toward the end of pregnancy, if development has been shed into the amniotic fluid and necessary. They include tests to assess placental function, fetal replaced by very fine vellus hair. Fetal movements are more growth, fetal heart rate, and fetal well-being. These tests may coordinated, and the fetus draws its arms and legs in toward be done in a hospital or an outpatient clinic. Examination of its body because space is limited. It has developed a number the mother’s abdomen will determine whether the fetus is in of primitive reflexes, such as turning toward familiar sounds a head-down position or if a breech presentation is likely. and strong light that filters into the uterus.

FUNDAL HEIGHT CHECK The height of the fundus above the pubis in cm approximates to gestation time. At 36 weeks, the height is around 14 in (36 cm).

PLACENTAL EFFICIENCY IMPROVED COORDINATION This 3D MRI scan shows a fetus This electron micrograph of nearing full term, at which time brain cells shows the density the placenta is becoming less of cell bodies (yellow) and efﬁcient at supporting it. dendrites (gray) at this stage.

ALVEOLI DEVELOPMENT The end sacs in the fetal lungs have matured into thin-walled alveoli. At birth, oxygen diffuses into the baby's capillaries.

170 123456789

WEEK 38 WEEK 39 What exactly triggers birth when the time is right remains Many mothers-to-be develop an urge to spring clean, a mystery. Changing hormone levels may be involved but, neaten the house, and prepare the nursery. This common increasingly, researchers believe the signal to start labor phenomenon is known as the nesting instinct. The mother’s comes from the fetus rather than the mother. The fetus’s flat breasts are preparing for lactation and have already started head bones are not yet fused, so they can slide over one to produce colostrum, which is rich in energy, antibodies, and another during birth, molding and elongating the head so that other immune-boosting substances. During the final days of it can safely pass through the birth canal. These bones spring pregnancy, the mother-to-be should take plenty of rest. Some back into shape soon after birth. The amount and length of parents already know the sex of their baby, but others will scalp hair varies from fetus to fetus. In some it is scant, and have decided not to find out before the birth. Choosing in others profuse. Head hair can be as long as 11/2 in (4 cm) or names for the imminent arrival, and talking to him or her, more. The fetus’s skin is now thicker and more robust. It has helps with bonding in advance of the birth. If either parent lost most of its greasy vernix coating although some usually has any outstanding concerns relating to the pregnancy or remains in vulnerable areas such as skin creases. birth, advice should be sought from a midwife or doctor.

READY FOR BIRTH SUCKING THUMB This 3D ultrasound image shows This ultrasound scan of a fetus a full-term fetus touching its at full term shows it sucking its eye. The full, chubby cheeks thumb, which may comfort it reﬂect healthy nourishment. and give practice for feeding.

WEEK 40 The average pregnancy lasts 280 days (40 weeks) from the ﬁrst day of the last period. Under 1 in 2 babies are still in the uterus at 40 weeks—more than half have been born. Toward ANTERIOR FONTANELLE the end, the cervix softens in preparation for the birth. It is To facilitate delivery, the skull common to feel backache, building pressure, and period-like bones slide over one another. pelvic cramps. Regular eating provides energy for labor, and The largest space (the anterior fontanelle) closes by 18 months. a warm bath or lower-back massage can ease discomfort.

CRAMPED CONDITIONS At full term the fetus has little room to move around, and the mother-to-be can detect its every twitch and hiccup.

171 CONCEPTION TO BIRTH

MOTHER AT 40 WEEKS MONTH 9 I WEEKS 36–40 The height of the uterus lowers during this month MOTHER as the fetus’s head “engages” MOTHER AND FETUS or settles into the pelvis, 75 beats per minute in preparation for delivery. 108/68 By 37 weeks, development is almost complete and the fetus Pressure eases on ribs Engagement or “lightening” 21⁄4pints (1.25 l) is considered “full-term.” It will still benefit from extra time in occurs during the ninth the uterus, however, and some babies are not born until 42 month and releases the pressure on the ribs, making weeks. The fetus is gaining weight, and its skin is shedding the breathing slightly easier. 1,000 lanugo hair that covered it from 23 weeks. In its place fine, soft The number of times the “vellus” hair is forming. The greasy vernix on its skin protects the Head presses on bladder capacity of the uterus can fetus from the increasing amounts of concentrated urine now The mother may experience increase by, compared with an increased urgency to a non-pregnant uterus. contained within the amniotic sac. Fingernails are growing fast, urinate, as her bladder is compressed by the position and they may need cutting soon after birth. The fetus’s practice- of the fetus’s head. breathing follows a regular rhythm, and it breathes quickly—around 25 oz (700 g) 40 times a minute. It may startle at loud sounds and will also The placenta now weighs recognize familiar voices. The mother’s uterus rises farther up the Pelvic joints loosen around 25 oz (700 g) and The pubic symphysis has a diameter of 8–10 in abdomen and increases the pressure against the diaphragm, which joint loosens to increase (20–25 cm), and a thickness flexibility, so that the baby 3 / 1 / can cause quicker, shallower breathing, fatigue, and indigestion. can travel through the of 4–1 4 in (2–3 cm). birth canal more easily.

1234567891011121314151617181920212223242526 27 28 29 30 31 32 33 34 35 36 37 38 39 40 STATISTICS FETUS 150 beats per minute 141⁄2–15 in (37–38 cm) 73⁄4 lb (3.5 kg) Under 5% The percentage of babies born on their due date. Endometrium Myometrium 30 percent are born earlier This powerful muscular than this date and 70 outer layer of the uterus is responsible for contractions percent are born later. during labor. Chorionic villi 96% The percentage of fetuses presenting in the upside- Perimetrium down position in the 40th Maternal artery week; 3 percent of fetuses are in the breech position, and the remaining 1 percent Maternal vein are in other positions. Amniotic ﬂuid The volume of this shock-absorbing liquid has reduced in the weeks leading up to birth.

Umbilical cord This connecting structure will be clamped and cut in the third stage of labor.

Weight gain The fetus continues to gain about 1 oz (28 g) a day during this month.

Amnion

Chorion

Skull bones These have not fused together yet, allowing changes in skull shape, which facilitates the passage of the baby down the birth canal. Mucus plug This plug of thick mucus THE FULL-TERM FETUS will loosen and fall out The shape of the uterus encourages the fetus just before labor starts. to settle in a head-down position, ready for Cervix birth. Although there is little free space, the This stays tightly closed fetus is cushioned by amniotic ﬂuid. The until birth is near; it will umbilical cord continues to deliver oxygen Vagina then begin to soften, and nutrients from mother to fetus, but thin, and then dilate. becomes less efﬁcient after 42 weeks. MONTH 9 I KEY DEVELOPMENTS

MOTHER

PRE-PREGNANCY BREAST ANATOMY THE PRODUCTION OF MILK The breasts develop during puberty and Toward the end of pregnancy, the breasts start to produce contain both fat and immature glandular a rich, creamy pre-milk called colostrum. This can tissue. Each breast contains 15–20 milk-secreting units known as lobules. occasionally be discharged from the nipples involuntarily

CONCEPTION TO BIRTH TO CONCEPTION during the third trimester. After delivery and with the removal of the placenta, levels of estrogen, progesterone, Pectoral muscles and human placental lactogen (HPL) suddenly fall. Secretory lobule However, prolactin levels remain high, and this is the Comprises hundreds hormone that stimulates full milk production. It is usually of microscopic alveoli; also contains advised that babies be put to the breast as soon as immature milk possible after birth. The suckling helps stimulate milk glands that drain into lactiferous duct production, and it is usual for milk to “come in” between the second and sixth day after delivery. Before this time, Areola babies receive small amounts of colostrum, which Pink-red-brown circular area provides energy, antibodies, and other immune-boosting surrounding substances. During the two to six days after birth, it is nipple normal for babies to lose as much as 10 percent of their birth weight before full production of mature milk begins.

Milk Produced by glands Nipple and secreted into Central saclike alveoli protrusion containing Secretory lobule 15–20 outlets Clusters of glands of milk ducts (lobules) group to form lobes Lactiferous duct Inactive channel LACTATING that will direct milk BREAST TISSUE toward nipple This light micrograph of healthy lactating breast tissue shows Rib Stroma the glandular spaces Connective tissue supports fat and (alveoli) into which Intercostal glands in breast milk is secreted by muscle specialized gland cells.

THE DELIVERY DATE 3,500 An estimated delivery date is calculated at the very KEY AVERAGE beginning of pregnancy based on the ﬁrst day of the last SMOKERS menstrual period. The age of the fetus is then assessed POOR NUTRITION from measurements taken during early ultrasound scans. This can sometimes result in a new estimated date of delivery. A singleton fetus is considered “full term” and 3,000 IMPACT OF ready to leave the womb from 37 weeks onward, LIFESTYLE although three additional weeks of growth—bringing Babies born after 35

BIRTH WEIGHT (GRAMS) BIRTH weeks of pregnancy gestation time to 40 weeks— to women who THE NESTING INSTINCT is usually beneﬁcial. If a fetus is smoke or eat a poor Toward the end of pregnancy, diet tend to have it is common for women to have still in the womb at 42 weeks, lower birth weights a strong urge to clean the house delivery is usually induced than average. This and prepare the nursery for the 2,500 can have an effect imminent arrival of the new because an aging placenta can 3436 38 40 on the future health family member. no longer function at its best. TIME (WEEKS) of the baby. WEEKS 36–40

LATE PREGNANCY BREAST ANATOMY As pregnancy proceeds, the breasts THE HORMONES INVOLVED IN LACTATION usually become larger and heavier. The size of the breasts is not related to the Like many aspects of pregnancy and childbirth, lactation amount of milk they can produce. occurs through a delicate interplay of hormonal activity. Some different hormones are secreted in addition to those already circulating in the pregnant body. Stroma Increasing bulk to Progesterone Progesterone is initially produced by the support growth corpus luteum (the empty egg follicle after of fat and glands ovulation) and then by the placenta. High levels of progesterone stimulate the growth of alveoli and lobules within the breasts. Secretory lobule Each lobule increases Estrogen Before pregnancy, estrogen is involved in in size and starts to breast development at puberty. Increased make colostrum estrogen levels during pregnancy are responsible for stimulating the growth and development of the milk duct system.

Prolactin Produced in the pituitary gland, prolactin promotes milk production (lactation). Darker areola Suckling the nipples causes release of From early prolactin so the breasts are constantly full. pregnancy, Oxytocin is usually secreted with prolactin. areola darkens and enlarges Oxytocin Oxytocin is secreted by the pituitary gland via an emotional trigger (baby crying) or stimulation of the nipples. Smooth muscle in the alveoli contracts and milk is ejected into the ducts—the “let-down” reﬂex.

Human placental Produced by the placenta from the second lactogen (HPL) month of pregnancy, HPL mimics the action of both prolactin and growth Nipple hormone, causing the breasts, nipples, Nipple darkens and areolae to increase in size. in color and may Cortisol Cortisol is present in relatively high amounts become more in colostrum during the ﬁrst two days of pronounced breastfeeding. As it falls, the level of protective antibodies in milk (IgA) increases.

Lactiferous duct Thyroxine Low amounts of thyroxine are present in Ductal system breast milk. This hormone is thought to expands and forms help prime the baby’s digestive system. branches to prepare for milk delivery

KEY AVERAGE DURATION OF PREGNANCY Quadruplets Full term PREMATURE Most pregnancies end about 280 days The average duration A fetus is (40 weeks) after the ﬁrst day of the woman’s TERM of a pregnancy in considered full Within a week last menstrual period. This measure of POSTMATURE which the mother is term at the end of Half of all babies are pregnancy is known as gestational age. carrying quadruplets the 37th week born within a week is 32 weeks. of pregnancy. of their due date. MONTHS 576 8910

18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45

GESTATIONAL WEEKS Youngest Viability Quintuplets Triplets Twins Within 2 weeks Induced labor premature birth The threshold The average The average The average The majority of Labor is usually The youngest of viability is the duration of a duration of a duration of a babies (90%) are induced by premature baby that point at which a pregnancy in which pregnancy in pregnancy in born within 2 weeks 42 weeks; has gone on to lead premature baby the mother is which the which the of their due date. otherwise, a normal, healthy life has a 50 percent carrying quintuplets mother is mother is placental was born at a mere chance of survival is 30 weeks. carrying triplets carrying twins deterioration 21 weeks and 5 days. outside the uterus. is 34 weeks. is 38 weeks. will occur.

175 BRAIN COMPONENTS In this color-enhanced THE FORMATION electron micrograph, each fetal brain cell has a yellow cell body and is surrounded OF THE BRAIN by many branching extensions, known as dendrites. These Starting as a small thickening of the embryo’s outer layer, the allow neurons to pass messages to neighboring brain becomes a highly complex organ by the time the baby is brain cells. born, containing 100 billion specialized cells known as neurons.

The ﬁrst sign of the developing nervous form at 13 weeks and is involved in system is a differentiation of cells to form regulating movements. The cerebrum the neural plate. This thickens and folds is the largest part of the brain and

THE FORMATION OF THE BRAIN I THE FORMATION to form the neural tube, the precursor to comprises two different tissue types: gray the brain and spinal cord. The three main and white matter. The former is the brain’s Neuron Dendrite cell body sections of the brain are evident within processing center, while the latter carries Axon six weeks. The cerebellum starts to information to different parts of the brain. Cerebrum Neural tube Ectoderm KEY Becomes brain Outer FOREBRAIN (PROSENCEPHALON) tissue layer MIDBRAIN (MESENCEPHALON) Neural Cerebellum crest Notochord HINDBRAIN (RHOMBENCEPHALON) Becomes Helps form SPINAL CORD peripheral spinal cord nervous Ear bud Brainstem CONCEPTION TO BIRTH BIRTH TO CONCEPTION Mesoderm system Middle tissue layer Cranial Endoderm nerves Inner tissue layer NEURAL TUBE FORMATION Somites Form the Forebrain skeleton prominence Ear bud

Eye Eye bud bud Pharyngeal Pharyngeal arches arches

5 WEEKS 6 WEEKS 9 WEEKS 13 WEEKS The neural tube forms in the The head end forms three hollow Swellings that will become the brainstem, The cerebral hemispheres expand and split into ﬁfth week from a groove that swellings that will develop into the cerebellum, and cerebrum grow at varying lobes. Connections start to form between brain folds in on itself. The expanding forebrain, midbrain, and hindbrain. rates and start to fold in on one another. cells. The hindbrain divides into the cerebellum neural tube at the head end The main divisions of the central The cerebrum divides into hemispheres. and brainstem, the latter of which is involved in forms the forebrain prominence. nervous system are now in place. Cranial and sensory nerves are forming. regulating basic functions such as breathing.

FISSURES AND RIDGES The cerebrum, the largest part of the NEURAL NETWORKS brain, is divided into the right and left cerebral hemispheres. During At birth, basic neural connections are higher mental functions develop, such development, each hemisphere enlarges in place, which help control vital as memory, increased attention span, forward to form a frontal lobe, upward functions such as breathing, heart language, intellect, and social skills. and sideways to form a parietal lobe, beat, digestion, and reflexes. As more By early adulthood, the complex and backward and underneath to form links form, and nerve cell axons neural network allows for reasoning, occipital and temporal lobes. As more become myelinated (insulated), judgment, and original thought. neurons climb up into the outer layer of the brain (the cerebral cortex), the surface develops folds to accommodate them. This results in the formation of shallow grooves (sulci), deep grooves (fissures), and convolutions (gyri). Each lobe forms its own major sulci, gyri, and fissures that can be identified in most individuals. For CORTICAL DEVELOPMENT example, the postcentral gyrus is the main This MRI scan of a 25-week-old fetus area where sensations from the body are reveals the complex folds in the developing AT BIRTH AGED SIX AGED EIGHTEEN interpreted, and the precentral gyrus is brain. Fissures and gyri can be seen clearly where voluntary movement is controlled. in cross section. 176 Prefrontal cortex Development of vision CONCEPTION TO BIRTH Contours of This influences planning, At birth, a baby can see the cortex decision-making, and shapes and patterns. The gyri and social behavior. Binocular vision develops fissures produce in the first month of life. Insula multiple wrinkles Gyri forming The insula, on the brain. Convolutions on which is involved Fissures forming the surface of the in emotional Grooves form fissures as brain, between the response, is found the surface of the fissures, are known deep within the cerebral cortex folds. as gyri. lateral sulcus. Frontal lobe This will influence speech, thought, emotions, skilled activities, and personality.

Pons Cerebrum

Cerebellum Medulla Pons

Cerebellum development The cerebellum coordinates movement and muscle tone.

25 WEEKS 40 WEEKS The surface of the fetal brain still looks smooth but the The surface of the cerebral cortex has become increasingly cerebral cortex is starting to fold to accommodate the complex to accommodate more brain cells. At birth, the rapidly increasing number of cells. From now until the brain contains 100 billion brain cells, but their connections ﬁrst few months after birth, the developing brain rapidly are not yet fully laid down. This part of the brain will not increases in size. This is known as the brain growth spurt. be fully mature until the person reaches the mid-twenties.

FORMATION OF GRAY KEY Majority of Layer 1 23–34 WEEKS Layers 1 and 5 separated MATTER VENTRICULAR ZONE cortex consists by cortical plate of subplate Support, or glial, cells in the WHITE MATTER neurons, Layer 5 developing brain act like scaffolding SUBPLATE important for establishing Layer 6 onto which newly divided brain cells CORTICAL PLATE Subplate (neurons) climb when emerging from correct wiring LAYERS 1–6 of cortex neurons begin 6 layers of the neural tube, in order to reach the Outer to disappear gray matter outer part of the cerebral hemispheres. edge of after 34 weeks now formed Here, in the so-called gray matter, the brain cortex begins to develop six layers of Layer 1 cells. Neurons climbing up the glial cells are thought to follow chemical THE SIX LAYERS signals that indicate the right point OF GRAY MATTER at which to jump off and begin Layers of neurons forming a layer. As the framework for develop until, by one layer is completed, the next wave birth, there are six of neurons climbs higher, through layers. Neurons here become the initial layers, to form a new layer specialized for 16–22 WEEKS NEWBORN on top. The way these layers form different tasks, such is vital for ordered thought processes as thinking, writing, Layers 2–6 will form Inner edge Subplate will disappear during in later life. and speaking. from cortical plate of cortex postnatal development 177 SIDE VIEW THROUGH FETAL BRAIN This MRI scan shows a side-view “slice” through the center of a 25-week-old fetus's brain. The face is to the left, and the two large dark areas are the nasal and mouth cavities. At this stage, connections are forming in the brain and it is starting to control body functions. FRONT VIEW OF FETAL BRAIN This MRI scan shows a front-view “slice” through the middle of a 30-week-old fetus's brain. The two hemispheres are clearly visible, and the surface of the brain—which remains fairly smooth until about 26 weeks—has become corrugated as the brain has grown. MONTH 9 I KEY DEVELOPMENTS

FETUS

FETAL SKULL BONES Frontal eminence Rapid brain development results in the head of Posterior a full-term fetus being 2 percent larger than the fontanelle Frontal or This space at the metopic suture birth canal. To overcome this problem, the fetal back of the skull has

CONCEPTION TO BIRTH BIRTH TO CONCEPTION brain is protected by a series of flat, soft skull usually closed up bones that have not fused and have the ability three months Anterior fontanelle after birth. This area between the to slide over one another. This allows the fetal parietal and frontal bones, skull to contract sufficiently to avoid damage as Occipital bone also called the soft spot, usually closes by 18 months. it passes through the birth canal. Two large spaces occur where the fetal skull bones meet at the front Sagittal suture Parietal eminence Coronal suture and back of the head—the anterior and posterior fontanelles. There are Lambdoid suture Anterolateral or four other fontanelles sphenoidal fontanelle at the sides of the skull. Posterolateral or This area forms between mastoid fontanelle the frontal, temporal, and Sutures are seams of This space is behind sphenoid bones. connective tissue where the ear, between the parietal and Maxilla the flat bones abut. temporal bones. The upper jaw (like the lower jaw) contains Posterior fontanelle teeth buds that slowly start to erupt after birth. SKULL AT 9 MONTHS VISIBLE FONTANELLE The skull bones of a Mandible This 3D ultrasound scan shows newborn baby are not fused. The lower jaw develops the posterior fontanelle, which The fontanelles and sutures are slowly to let the baby forms in the space between protected by tough membranes latch onto the breast the occipital bone and the that turn to bone (ossify) during and suckle. two parietal bones. the first two years of life.

INCREASED COORDINATION SPECIALIZED MONITORING Nerve cells (neurons) in the brain of a fetus As the fetus approaches full term, the mature placenta multiply at an astonishing rate of 50,000– becomes less efﬁcient at providing all the nutrients 100,000 cells per second. The gray matter, required for growth and sustenance. A range of different or cortex, of the brain develops in tests is used to assess whether the fetus is being deprived successive layers. When the framework nutritionally. These tests help assess fetal growth and for one layer is completed, the next wave well-being and may check breathing, movement, and of neurons emerges to form a new layer heart rate. They require specialized equipment and are on top. As the brain rapidly enlarges, usually carried out in a hospital or an outpatient clinic. these brain cells make more and more connections with other brain cells, and the TESTS TO ASSESS FETAL HEALTH coordination of fetal movements improves TEST DESCRIPTION and becomes ever more complex. PERFORMED Nerve cell body Control center Fetal growth If the fetus is growing slowly, ultrasound scans are carried housing the nucleus out regularly. The circumference of the fetal head and size of the liver are measured, as well as the thigh bone (femur) Dendrite length. If the placenta is not working well, the fetal head will Communication ﬁber seem relatively large compared with the liver, because the that disperses impulses baby’s fat stores are used up (or have not been laid down).

NEURONS INVOLVED Fetal well-being A biophysical profile assesses fetal well-being by monitoring WITH MOVEMENT the heart rate on a cardiotocograph (or CTG) and by using This color-enhanced electron ultrasound to record the amount of amniotic fluid, the fetus’s ABDOMINAL EXAMINATION micrograph shows fetal movements, extensions of the limbs, and breathing. This A healthcare professional carries brain cells (green) in the part profiling is carried out if the fetus is not growing as expected out an examination on the of the brain that controls and if the blood flow in the umbilical arteries is poor. abdomen of a woman whose posture and movement. fetus is full term. 180 WEEKS 36–40 TIGHT FIT the end of Toward is there pregnancy in the left little room uterus. stretched fully Although bunched still can up, the fetus within around move of sac its protective amniotic fluid. NEWBORN BABY PHOTOGRAPH OF PHOTOGRAPH 3D ULTRASOUND 3D ULTRASOUND OF FULL-TERM FETUS OF FULL-TERM A comparison A comparison a 3D between of scan ultrasound a fetus of the face and the sameinfant birth reveals after of the accuracy imaging. prenatal BEFORE AND AFTER BIRTH At nine months the fetus is fully formed and its head is in proportion the fetus is fully formed and its head nine months At been Increasing amounts of fat have laid body. with the rest of the hasdown, and the face it appear lost most of its wrinkles, making which is especially vernix, in protective covered plump. The fetus is of body such as the armpits. Small amounts thick in skin creases hair (lanugo) be still may present but these disappear soon after birth. The fingernails and toenails extend to grown and may are almost fully to lie with its arms and legs the ends of the digits. The fetus tends with its fingers. Many—but up and can grip quite strongly drawn not all—babies position are now in the head-down ready for birth. FINAL DEVELOPMENTS CONCEPTION TO BIRTH THE MOTHER’S CHANGING BODY A woman’s body undergoes profound changes during pregnancy. A number of these changes are beneficial, such as the development of stronger nails and a glowing complexion, but there are also some potential discomforts, such as back pain, breathlessness, and fatigue.

The mother’s body must supply the developing 80 120 6,000 fetus’s rising demand for oxygen and nutrients, 75 creating increased work for her own lungs, 100 5,500 Systolic Rapid rise in blood heart, and digestive system. In addition to 70 (maximum pressure) volume occurs between months 6 and 8 carrying the baby, her body must support the Heart rate increases 80 5,000 growth of the placenta and production of 65 in steps and eventually levels HEART RATE (bpm) RATE HEART amniotic ﬂuid. As the pregnancy progresses, out in month 9 60 (ml) VOLUME BLOOD 4,500

60 (mmHg) PRESSURE BLOOD the uterus expands upward and outward Diastolic (minimum pressure) to push against her intestines and diaphragm. 55 40 4,000 Her breasts begin to enlarge in preparation 0 48 12 16 20 24 28 32 36 40 0412162024283236408 0 48 1216202428323640 GESTATION (WEEKS) GESTATION (WEEKS) GESTATION (WEEKS) for lactation, and her blood volume, body HEART RATE BLOOD PRESSURE BLOOD VOLUME fluids, and fat stores increase. Altogether, Maternal heart rate increases during pregnancy Blood pressure tends to go down during the early Blood volume increases steadily in pregnancy in response to increased blood volume and the stages of pregnancy and then increases during (until around 32 weeks, when it tends to level these changes account for a normal weight extra work performed by the heart as it pumps the last trimester. Changes in posture, such as off) to allow extra blood flow to the uterus and gain of around 22–29 lb (10–13 kg). blood through the placenta. lying flat on the back, can affect blood pressure. other maternal organs, especially the kidneys.

WEEKS 1 2 3 4 5 6 7 8 9 10 11 12

During this month, the mother may not The mother has usually missed a period As the ﬁrst trimester ends, the uterus grows even be aware that she is pregnant. The ﬁrst by now and knows she is pregnant. Breast to reach the top of the pelvic cavity. Vaginal sign is usually a missed period. Some women tenderness, areolae enlargement, increased discharge may increase. Blood volume has 123notice changes in taste sensation, tingling of urinary frequency, and food cravings may increased, and some women already have MONTH MONTH MONTH breasts, nausea, or unusual fatigue. occur. Fatigue is also common. a healthy pregnancy glow. WEEKS 13 14 15 16 17 18 19 20 21 22 23 24 25 26

The enlarged uterus can be felt by abdominal The top of the uterus is level with the belly Fetal movements are often first felt between examination. The breasts are enlarging, and button. Some women develop a pigmented the fifth and sixth months. The mother’s sex the nipples and areolae darken due to rising line (linea nigra) running down from the drive may increase due to increased pelvic 4 levels of estrogen. Nausea starts to subside. 5 navel. Patches may develop on the face 6 blood flow. The hormone progesterone can MONTH Some women may look pregnant. MONTH (chloasma), but fade after delivery. MONTH slow bowel activity and cause constipation.

WEEKS 27 28 29 30 31 32 33 34 35 36 37 38 39 40

Rapid abdominal expansion and hormone Fat stores may be deposited in odd places: If the fetal head “engages,” pressure may changes can lead to stretch marks on the between the shoulders, on the upper back, be felt in the pelvis. Increasing fatigue is abdomen, thighs, buttocks, or breasts. As around the knees. If the uterus compresses normal. The breasts are making colostrum. As 7 the uterus pushes up against the intestines, 8 the diaphragm, deep breathing is difﬁcult. 9 the cervix softens, loss of the cervical mucus MONTH indigestion and heartburn can occur. MONTH Braxton-Hicks’ contractions may occur. MONTH plug may show that delivery is imminent. CONCEPTION TO BIRTH THE FETUS’S CHANGING BODY The 40 weeks of pregnancy encompass the remarkable transformation of a single-celled fertilized egg to a breathing baby. During this time, the 11 major systems of the body take shape, undergoing predictable periods of growth and development.

The organization of the baby’s body is incredibly complex. down during the ﬁrst eight weeks of life—the embryonic Each of its trillions of cells communicates with its neighbors, stage—after which the embryo is known as a fetus. By the TIMELINE OF MAJOR EVENTS Each of the 11 major body systems undergoes following chemical and hormone signals that direct its end of the second trimester, the fetal systems have developed speciﬁc stages of growth, which occur in a movements and the kind of cell it will become. These to the point at which it has a chance of survival if born predictable sequence. Most of the fetus’s body systems are mature enough to function interactions depend on the genes inherited from the parents. prematurely. The third trimester is a period of rapid growth, after 37–40 weeks of development, when it is The basic blueprint for each of the body systems is laid helping prepare the fetus for the world outside the uterus. considered “full-term.”

TRIMESTER 1 TRIMESTER 2 TRIMESTER 3

WEEK 12345678910111213141516171819202122232425262728293031323334353637383940

WEEK 6 WEEK 7 WEEK 8 WEEK 10 Limb buds form Nostrils form; Vertebrae and ribs Ossification (bone WEEK 24 WEEK 39 limb buds established; toes separate; formation) begins; WEEK 22 Skeleton more in Midsection of long WEEK 5 flatten and bone starts to form neck lengthens WEEK 14 Bones in ear proportion: head, WEEK 37 bones ossified, but Somites (future form digits; Spine harden, leading trunk, and legs Ossification is ends of bone, and vertebrae, muscle, elbows form WEEK 9 WEEK 13 straightens to sense of account for one-third occurring in humerus, tips of finger and toe and skin) form Digits all formed All joints present out balance of fetus’s length femur, and tibia bones still cartilage

5 678910 1314 2224 3739 SKELETAL SKELETAL SYSTEM

WEEK 8 WEEK 13 WEEK 31 Spinal musculature WEEK 10 Weight starts to increase WEEK 23 Muscle mass and trunk wall muscle Tongue now rapidly from now on; a large Eyelids become continues to layers develop developed proportion of this is muscle well developed develop rapidly

8110 3 23 31 MUSCULAR SYSTEM

WEEK 16 WEEK 7 WEEK 12 WEEK 14 WEEK 27 WEEK 38 Taste buds Cerebral Motor WEEK 25 Eyelids no Eyes Spinal cord reach maturity WEEK 5 hemispheres neurons start WEEK 13 extends full Smooth longer fused WEEK 29 WEEK 34 three-quarters Spinal cord and WEEK 6 form; ears to mature; Myelin-sheath length of WEEK 18 surface of together; Electrical activity Suckling of adult size; brain begin Eyes start begin to cerebellum development vertebral canal Eyes and ears arrive brain begins sensitivity to registered in reﬂex they cannot to form to form appear starts to form starts at ﬁnal position to wrinkle light develops cerebral cortex develops yet focus

5 6 7 12 13 14 16 18 25 27 29 34 38 NERVOUS NERVOUS SYSTEM

WEEK 24 WEEK 25 WEEK 9 WEEK 12 WEEK 14 High metabolic rate leads to Adrenal glands release WEEK 6 Thyroid moves Insulin Thyroid gland higher temperature than steroid hormones, such WEEK 31 Pancreas from base production has matured and mother; fetus lays down brown as epinephrine, which Pituitary gland in begins to of tongue begins in starts to produce fat, which provides energy prepares baby for the brain releases form to neck pancreas hormones and heat after birth stresses after birth growth hormone

6 9 12 14 6 24 25 31 ENDOCRINE SYSTEM REPRODUCTIVE URINARY DIGESTIVE LYMPHATIC AND SKIN, HAIR , RESPIRATORY CARDIOVASCULAR SYSTEM SYSTEM SYSTEM IMMUNE SYSTEMS NAILS, AND TEETH SYSTEM SYSTEM (future kidney) appear Lungs beginto form from Formation of Stomach beginsto form; appear; liver cells appear the yolk sac Diaphragm beginsto form pancreas andbile ducts Primitive heart bud offoesophagus WEEK 4 Ureteric buds tube forming Bladder andurethra Spleen appears WEEK 5 WEEK 6 begin to form 45 Gonadal ridge develops; WEEK 8 genitalia ofmale and WEEK 6 WEEK 6 WEEK 9 WEEK 9 female fetuses still indistinguishable Sweat glands 8 6 01 314 13 11 10 9 6 6 6 6 not to placenta of fetus, but around length Blood pumped WEEK 6 WEEK 8 WEEK 8 develop completed Diaphragm formation WEEK 10 7 and form abulge Bowels lengthen WEEK 7 rectum; kidneys move towards separate from Bladder now 8 8 81 81 810 Rectum appears WEEK 8 begins to form Lymphoid tissue WEEK 8 abdomen WEEK 10 01314151617 10 9 91 of tooth buds development Early WEEK 9 WEEKS 13–14 Fetus startsto vessels formed all majorblood complete, with development Heart WEEK 8 make inhaling and exhaling movements evident differentiation Signs ofgender WEEK 10 11 within abdominalcavity Intestines andbowel now WEEK 11 begins production Urine WEEK 11 to three layers; 1 2 follicles begin starts to form Meconium (first stool) WEEK 12 Skin thickens Lungs continue glands inlungs to develop to branch and divide; mucus produced by WEEK 15 13 1 3 first hair at combating infection and spleen, butare noteffective produced inliver, thymus, First white bloodcells WEEK 13 clots break down make and Blood can WEEK 13 WEEK 15 every 30minutes Bladder fillsandempties WEEK 13 Uterus, vagina, and period ofdevelopment Kidneys enter crucial WEEK 14 develop ingirls fallopian tubes 5 fingerprints and WEEK 17 fully developed Dermal ridges, toe prints,are which lead to 617 16 2 6 of heart muscle increased strength ultrasound dueto be heard on Heart rate can WEEK 16 movements andhiccups start Regular breathing WEEK 16 WEEK 18 17 20 Bronchioles beginto form WEEK 17 reaches colon Meconium WEEK 16 1 8 under skinlaid becomes less Layer offat 9 translucent down; skin WEEK 21 protection from viruses to fetus, affording some transferred from mother Immunities beginto be WEEKS 19–20 2 0 begin to descend into scrotum gonads turninto testes, whichnow now descend into thepelvis; inboys, each containing sixmillioneggs; ovaries In girls,gonads change into ovaries, WEEK 20 by bonemarrow being produced platelets start blood cells and Red andwhite WEEK 17 2 1 1 functional becomes fully Anal sphincter WEEK 21 2 23 32 dioxide transfer easier oxygen andcarbon alveoli thins,making bloodstream and Barrier between WEEK 23 in lanugo andvernix fetus now covered to become visible; keratinize; nailsbegin Skin beginsto WEEK 23 73 lengthen on head beginsto considerably; hair eyelashes grow Eyebrows and WEEK 27 Bladder volume is amniotic fluidswallowed, aiding gutdevelopment approximately minutes, thenempties; 17 fl oz (0.5 l) perday of 1 Stomach fillsevery 40 / 3 fl oz (10 ml) (10 fl oz WEEK 32 30 30 from motherto fetus efficiently transported Immunities now WEEK 30 to produce them and spleen docontinue marrow, althoughliver now made by bone Majority ofbloodcells WEEK 30 WEEK 32 (alveoli) from collapsing— 5 reducing surface tension concentrated due 1 to further kidney in someraces, skinchanges from red to pink Skin becomes thicker andless translucent; WEEK 31 and preventing airsacs Urine now more Surfactant—chemical development 3 23 739 37 36 32 3 23 23 tips offingers Fingernails reach WEEK 32 WEEK 36 now produced 3 possible of food is which digestion to pointat Gut developed WEEK 33 WEEK 35 34 Fetus urinates body weight 1 35 / 4 WEEK 37 – after birth sacs allow gas exchange fine vessels nextto air completes development; Blood supply to lungs WEEK 34 1 per day / 3 ofits 6 Regular breathing completely entered replaced by vellus hair Lanugo hairalllost; WEEK 36 mature enough Testes have now pattern of40 to take over WEEKS 39–40 Liver isnow the scrotal sac breaths per established metabolic WEEK 39 WEEK 39 WEEK 39 functions is 1 Bladder volume minute 1 (40 ml) (40 / 2 floz 39 940 39 3 9 AN INCREDIBLE SERIES OF CHANGES TAKES PLACE IN THE MOTHER AND FETUS OVER THE COURSE OF PREGNANCY, CULMINATING IN THE MOST REMARKABLE OF EVENTS: BIRTH. THE BEGINNING OF THIS PROCESS—LABOR—STARTS WHEN THE MUSCULAR WALL OF THE UTERUS CONTRACTS WITH INCREASING STRENGTH AND FREQUENCY, PUSHING THE BABY DOWN AND OPENING THE CERVIX IN PREPARATION FOR THE BABY’S PASSAGE THROUGH THE BIRTH CANAL. THE BABY TWISTS AND TURNS AS IT DESCENDS, THE BONES OF ITS SKULL SHIFTING SLIGHTLY TO ENABLE THE HEAD TO PASS THROUGH. THE FIRST BREATH TRIGGERS IMMEDIATE CHANGES IN THE BABY’S LUNGS AND HEART, HERALDING THE START OF INDEPENDENT LIFE. LABOR AND BIRTH PREPARING FOR BIRTH During the final weeks of pregnancy, hormonal changes in the mother and the pressure of the fetus as it moves down in the pelvis prepare the uterus for the imminent birth.

EARLY CONTRACTIONS In the second trimester, very mild contractions begin to occur in the uterus, which gradually increase in intensity and frequency over the course of pregnancy. These painless tightenings, known as Braxton Hicks’ contractions, tend to last about 30 seconds each. They cause an increase in blood ﬂow to the placenta, thereby increasing the delivery Braxton Hicks’ contraction of oxygen and nutrients to the Mild, irregular contraction occurring from mid-pregnancy fetus in its ﬁnal stages of growth. PREPARING FOR BIRTH I PREPARING LABOR AND BIRTH

Close to birth, Braxton Hicks’ INTENSITY OF CONTRACTION contractions can become uncomfortable, and some 0 10 20 30 TIME (MINUTES) women, particularly with their 20TH WEEK OF PREGNANCY ﬁrst baby, mistake this “false” labor for the onset of true labor. More frequent contractions While still mild, CONTRACTIONS contractions are more Braxton Hicks’ contractions become regular in the ﬁnal weeks INTENSITY OF more frequent as a pregnancy progresses. CONTRACTION Although distinctive in character, they are the forerunners of the strong, regular 0 10 20 30 contractions that herald the onset of true TIME (MINUTES) and established labor. 36TH WEEK OF PREGNANCY

THE LATENT PHASE This very early part of labor is characterized by mild and irregular contractions. These contractions cause the changes in the cervix necessary 3 for birth, making it softer, thinner, and much shorter than its original /4 in (2 cm) length. The latent phase tends to last around eight hours, but can be shorter in women who have had several babies. The mild contractions may be felt as backache or menstrual period-type pain and do not usually cause distress. Some women are unaware that this phase is taking place. With the onset of established labor (see p.190), the opening (dilating) of the cervix begins, caused by the stronger and more frequent contractions that occur.

SOFTENING OF THE CERVIX The mild contractions of early labor cause the cervix to soften and shorten, a process that must take place before the cervix can open up to a sufﬁcient size to allow the fetus’s head to pass through.

Lower segment of uterus

Mucus plug ﬁts tightly

Cervix shortening

THINNING OF THE CERVIX As the mild contractions of early labor continue and the fetus’s head presses against the cervix, it gradually thins and merges into the wall of the uterus above before starting to open, or dilate.

Cervix merging with uterus

Mucus plug loosens

Cervix becomes shorter and wider 188 PREPARING FOR BIRTH FETAL LIE The fetus can lie in a vertical, horizontal, or diagonal position in the uterus. A vertical lie can be cephalic (head-down) or, less commonly, breech (bottom-down). With a horizontal or diagonal lie, there is no presenting part. By 35 weeks, most babies will be in the cephalic position. At term, 95 percent of babies are cephalic, 4 percent breech, and 1 percent transverse (horizontal) or oblique (diagonal). LABOR AND BIRTH I LABOR

Uterus Placenta

Extended Uterus legs Head Knees positioned straight by side wall of uterus Buttocks present ﬁrst Back presents Cervix ﬁrst

FRANK BREECH In this type of breech position, TRANSVERSE LIE the legs lie in front of the fetus, This is more common in women who have already in contrast to complete breech, had a baby. The looseness of the uterine muscles where the fetus sits cross-legged. allows the fetus to lie horizontally across it.

ENGAGEMENT The term “engagement” is used when three-ﬁfths or more of the fetus’s head has passed through the pelvic inlet. By feeling the abdomen, the physician or midwife can assess how much of the head lies above the pubic bone at the front of the pelvic inlet and determine whether the head is engaged. During labor, engagement is assessed by vaginal examinations.

Head sits in pelvis Uterus Cervix Pelvic inlet

BEFORE THE HEAD ENGAGES AFTER ENGAGEMENT If three-fifths or more of a fetus’s head lies above Once two-fifths or less of the head lies above the the pelvic inlet, it is not engaged. Most first babies pelvic inlet—with most of it lying below—the engage at about 36 weeks. Some babies’ heads do head is engaged. The fetus is able to move down not engage until after the beginning of labor. because the lower section of the uterus expands.

LATE-PREGNANCY HORMONE CHANGES

Estrogen levels rise in the last weeks of pregnancy, while progesterone levels stabilize. Estrogen triggers CHANGING contractions of the uterus, while LEVELS progesterone loosens joints to ease KEY The last weeks the passage of the fetus through the ESTROGEN of pregnancy see PROGESTERONE increasing levels HEAD-DOWN POSITION pelvis. Levels of hCG do not change LEVELS BLOOD of estrogen, Known as cephalic presentation, this is the significantly after the fourth month HCG stabilizing levels best and most common position for vaginal because this hormone’s principal role delivery. The head (the presenting part), of progesterone, of maintaining the corpus luteum in 28 3032 34 36 38 40 which reaches the cervix first, is the most and a very slight effective part at dilating the cervix. the ovaries has been fulfilled by then. WEEKS OF PREGNANCY fall in hCG.

189 THE FIRST STAGE OF LABOR This period of labor is characterized by the onset of regular, painful contractions and is complete when the cervix is fully dilated to allow the baby to pass through. During this stage, contractions become stronger and closer together.

EARLY SIGNS OF LABOR UTERINE CONTRACTIONS FIRST STAGE OF LABOR STAGE FIRST Before the ﬁrst stage of labor becomes established, In the early part of the ﬁrst stage, contractions there are mild and irregular contractions (see p.188). are very mild and produce only a small amount These are then overtaken by strong, regular of cervical dilation. Later on, in established labor, contractions. As labor approaches, the mucus plug the forceful contractions drive the baby down that has been present in the cervix throughout toward the cervix, which opens at a much faster pregnancy is dislodged (and is then known as the rate. The muscles of the uterine wall have a rich “show”). The waters usually break during labor or supply of blood. With each contraction, the just before it begins. Occasionally, the waters break blood vessels that supply oxygen and nutrients prematurely, before 37 weeks. to the muscles are squeezed, reducing the oxygen LOWER ABDOMINAL PAIN supply and causing pain. This pain becomes With the onset of strong contractions

LABOR AND BIRTH I THE LABOR AND BIRTH comes pain in the lower abdomen and Placenta more severe as contractions become stronger often in the lower back. There are a number and more prolonged. of options to help ease the discomfort. Uterine wall Fundus Placenta Umbilical cord Amniotic sac Point at which Delivers nutrients Continues to be contractions of and oxygen during a lifeline for established labor the ﬁrst stage baby commence

Muscle ﬁber THE “SHOW” contraction 1 This leakage of Causes pain as mucus, often tinged muscle ﬁbers with blood, occurs shorten before labor begins, when the plug that Mucus plug seals the entrance to ejected the uterus comes out.

Fundus CONTRACTIONS 2 The mild contractions of very early labor are slowly replaced by stronger and more painful contractions that last progressively longer.

Contractions spread from fundus Cervix dilates

Bulging amniotic sac

WATERS BREAK ANATOMY OF A 3 This is when the CONTRACTION amniotic sac that Contractions in early labor are surrounds the baby concentrated in the muscles of tears and clear, the lower uterus, but the painful, straw-colored ﬂuid regular contractions of established leaks out through labor begin at the top of the uterus the cervix. (the fundus) and spread downward.

Contractions continue

Amniotic fluid drains out through birth canal 190 THE FIRST STAGE OF LABOR CERVICAL DILATION During labor, the cervix opens to 4 in (10 cm) wide. Early on, the THE TRANSITION PHASE physician or midwife performs a vaginal examination to assess various aspects of the cervix, including degree of dilation, length, consistency, For some women, there is a period of time between full dilation and the onset of the urge to push. Known as the and position. How far the baby has descended into the pelvis is also transition phase, it may last a few minutes or as long as recorded, as well as the baby’s lie (see p.189). Throughout the first stage, an hour. The contractions are very strong and frequent the mother is assessed regularly, both with abdominal and vaginal during this stage, so it can be difficult for the mother examinations, to ensure that adequate progress is being made in as she waits for the second stage of labor to begin. terms of cervical dilation and descent of the baby into the pelvis. 70 seconds 50 Height of

contraction AND BIRTH I LABOR 45 40 Contractions become painful when pressure 35 rises above this line 30 INCREASED AMNIOTIC PRESSURE 25 4 in The contractions of the 3 1 /4 in (2 cm) 2 /4 in (6 cm) (10 cm) PRESSURE AMNIOTIC 20 transition phase are dilated dilated dilated extremely intense, and 15 INITIAL DILATION CERVIX WIDENS FULLY DILATED the pressure within the In the early stages of labor Once labor is established Once the opening is 4 in 10 uterus rises to very high 1 2 3 0 1 2345 the cervix opens slowly, as the and the contractions are (10 cm) across (fully dilated), the levels, then falls down uterine contractions are still effective, the cervix dilates mother can soon begin to TIME (MINUTES) again rapidly. 1 mild at this stage. from 1 /2 in (4 cm) to 4 in (10 cm). push the baby out.

Fundus FETAL MONITORING Softens as muscles Muscle ﬁber relax between relaxing The main indicator for fetal well-being during labor is the rate contractions This lengthens the muscles into the of the fetal heart and how it ﬂuctuates in response to contractions. relaxed state The simplest methods used to listen to the fetal heart are a Pinard BETWEEN CONTRACTIONS stethoscope or a hand-held sonicaid machine, both of which are Welcome moments held against the mother’s abdomen. Electronic fetal monitoring of respite between Cervix is used over longer periods, contractions give Dilated by the mother a pressure usually with two monitors chance to breathe from the strapped to the abdomen. more easily and try baby’s to relax before the head Sometimes the heart rate is next contraction. monitored via an electrode These periods become shorter as attached to the baby’s head. labor progresses.

ELECTRONIC FETAL MONITOR This measures the fetal heart rate and the intensity of contractions. Two sensors are linked to a cardiotocograph machine, which shows the results on a continuous trace.

Peak of Pubic contraction MATERNAL bone Bladder Becomes more CONTRACTIONS compressed as the These regular baby moves down contractions are typical of a normal labor. As revealed by the trace, INTENSITY OF Vaginal rugae CONTRACTIONS they gradually increase Make up the corrugated 0 1 2 3 4 5 6 7 8 9 10 11 in intensity. lining that allows vagina to stretch Heart rate increases with each contraction 160

Skull bones 140 FETAL HEART BEAT Can move, to allow The heart rate is head to change shape constantly ﬂuctuating, during delivery 120 and a certain degree of

PER MINUTE variability indicates that a Cervix FETAL HEART BEATS BEATS HEART FETAL 100 baby is active and coping Softens and thins; well with the labor. The dilates as head of baby rate increases when presses against it 80 0 1 2 3 4 5 6 7 8 9 10 11 contractions occur. Rectum TIME (MINUTES) 191 THE BIRTH BIRTH The second stage of labor is the birth, culminating in the emergence of a new human being. Great effort from the mother, together with strong, Shrinking uterus frequent contractions, are needed to push the baby down the birth canal. The top of the uterus lowers as the baby moves down through Wall of uterus The second stage begins once the cervix is fully dilated, the pelvis. contractions are strong and regular, and the woman has the desire to push. The baby rotates and the position of its head changes as it passes down the birth canal so that the widest

LABOR AND BIRTH I THE LABOR AND BIRTH part of its head is in line with the widest part of the mother’s pelvis. Once the head has emerged, the baby turns again so that its shoulders can come out easily, one after the other. As soon as the baby emerges, the umbilical cord is checked to

Pelvis Vaginal make sure it is not around the baby’s neck, and mucus is opening cleared from the baby’s nose and mouth to aid the baby’s POSITION OF THE BABY IN THE PELVIS breathing. The birth typically lasts about one to two hours.

Intense contractions Contractions are strong and frequent during the delivery, HEAD and pushes by EMERGES the mother are 2 Crowning is the timed to coincide with them. ﬁrst appearance of the baby’s head, which is tilted backward as it comes out of the birth canal. The head is the Placenta widest part of the baby, and The placenta once it emerges the rest of the remains attached body will follow relatively easily. to the wall of the The baby’s head may appear uterus during the misshapen after the delivery, but its delivery and starts shape will become normal with time. to detach after the baby is born.

Umbilical cord The umbilical cord stretches as the baby moves down the birth canal.

THE DESCENT 1 With the contractions of the uterus, the baby moves gradually down through the pelvis. The baby’s head is tilted forward toward its chest as it pushes down into the birth canal. The baby’s arms and legs are tucked into the body to make it is as compact as possible Pubic symphysis on the journey down the birth canal. Joint uniting left and right pubic bones; increasing secretion of relaxin hormone softens it to make the pelvis more ﬂexible during birth.

Vaginal opening

Crown The top of the baby’s head; crowning is when it first appears during birth. 192 THE BIRTH I LABOR AND BIRTH 193 Shoulders emerge Shoulders shoulders The baby’s soon after emerge and are the head by followed swiftly of the body. the rest GYNECOID PELVIS GYNECOID has pelvis The gynecoid wide, and a round, shape with a shallow inlet. This wide pelvic shape is favorable the enlarging for and uterus pregnant pass to the baby for during labor. through PELVIS ANDROID is pelvis The android deeper, triangular, more with a and narrower, inlet. pelvic smaller can These features a for problems present unless delivery vaginal is small. the baby in (12 cm) 2 / 1 Shrinking uterus shrinks The uterus further as the down and emerges head continues the baby down. move to Pelvic inlet 4 inlet Pelvic Pelvic inlet 5 in (13 cm) in (13 5 inlet Pelvic comes out. comes Head support Head be supported as it The emerging head head The emerging rotates again and must again rotates Stretched vaginal tissue vaginal Stretched and The lining of the vagina muscles the surrounding which corrugated, are stretch to the vagina allows through. passes as the baby SHAPES PELVIC There is considerable normal variation in the shape of the female pelvis, some shapes making vaginal easier delivery than others. The gynecoid pelvis is the “typical” female shape and offers the best chance of a problem-free The android vaginal delivery. pelvis is a similar shape to the male pelvis and has a fairly narrow pelvic inlet, which make a vaginalmay delivery more difficult. If the pelvis is not big enough to let a baby pass through, the condition is known as cephalopelvic disproportion (CPD). Malleable Malleable skull bones The fontanelles and sutures the between skull bones allow some flexibility in the skull as it through passes the birth canal. Superior pubic ramus of the The upper branch pubic bone. Body facing Body facing backward the faces The baby spine as its mother’s through passes head the birth canal. Once the head has been the head Once ROTATION delivered, the baby’s body the baby’s delivered, out pass it to allow to rotates each With of the birth canal. is repositioned turn, the baby it is in the best position so that are the shoulders delivery; for slide out can aligned so they one, then the other. first easily, 3 Ischiopubic Ischiopubic ramus The lower of the branch pubic bone. Obturator Obturator foramen between Hole the pubic bones; covered usually a membrane by with muscles to attached either side SECONDS AFTER BIRTH This healthy newborn baby girl is pictured only a few seconds after being been born. Her skin is covered in a waxy coating (vernix), and she is crying, which inflates her lungs. The umbilical cord will be clamped; its stump will fall off naturally in one to three weeks.

Amniotic sac BIRTH POSITIONS If present, the There are many possible options for the position in which to go through second sac may stay intact during labor and give birth. Many women find it helpful to move around during the the first birth. first stage of labor, and then to try one of a number of positions that are better for delivery than simply lying flat on the back. Some women feel more comfortable sitting on a bed with their back supported by pillows, whereas others prefer to kneel, squat, or use a birthing stool. THE BIRTH I LABOR AND BIRTH THE BIRTH

SITTING UPRIGHT KNEELING SQUATTING This position, supported behind The woman can kneel upright with When squatting, the pelvis is by pillows, can be comfortable support or on all fours. Gravity can opened up, which, with the aid and good for pushing because the be helpful in upright positions in of gravity, makes it easier for woman can pull against her thighs. aiding the descent of the baby. the baby to be delivered.

Umbilical BREECH BIRTH cord Many women with a breech presentation (see p.189)—in Placenta which the baby presents buttocks-first—have a cesarean section. However, a vaginal delivery may be considered in some cases, although it may not be possible to continue if problems develop, such as a cord prolapse (see p.232), in which the umbilical cord FEET FIRST In a breech birth, the baby’s comes out first. If the cord is buttocks and legs appear first, compressed, this can deprive followed by the body. The widest part of the baby, its the baby of oxygen and cause head, appears last. fetal distress or death (see p.232).

PAIN RELIEF Gas and air Drug injections

There are a number of options Commonly known as Entonox (a The analgesic drugs used during labor are common but stadol and nubaine are also available for pain relief in labor. brand name), gas and air consists either administered by injection or through used. All have potential side effects, Some have a generalized effect, of a combination of oxygen and an IV tube. They act by relieving pain but they are often chosen because they relieving pain and having effects nitrous oxide and is often used to throughout the body and tend to be given are easy to administer and relieve pain all around the body. These include provide pain relief during labor. early in labor. Morphine is the most relatively quickly. opioid analgesics, the most Entonox can be given through a commonly used being morphine mouthpiece or through a mask. TYPE HOW IT WORKS SIDE EFFECTS as well as drugs derived from When using gas and air, the woman morphine. In contrast, the effects should inhale and exhale with Morphine Morphine may be given by injection into Nausea, vomiting, and of regional analgesics are largely deep, regular breaths. It does not a muscle or through an IV tube inserted sedation in the mother; into the arm and attached to a pump that sedation and depressed limited to one area of the body. completely eliminate the pain but the woman controls herself (known as breathing in the baby. There are also other, nondrug reduces it while also helping the patient-controlled analgesia). methods, which may help with woman to feel calmer. The effect relaxation as well as pain control. begins to be felt after about 30 seconds, so the woman must Stadol Like morphine, Stadol is given by IV Effects are similar to those of injection. morphine, but it is effective start breathing it as soon as a for a shorter period of time. contraction starts to feel the beneﬁt at the right time. Gas and air can cause nausea and lightheadedness, but the effects wear off quickly. Nubaine Nubaine is also given by IV injection. Effects are similar to those of morphine, but it is effective Gas and air is not used in some for a shorter period of time. countries, including the USA.

196 LABOR AND BIRTHLABOR MULTIPLE BIRTHS IMMEDIATELY AFTER THE BIRTH Placenta In the majority of cases, multiple births are delivered by cesarean Within seconds of being born, the baby will section, although a vaginal delivery may be attempted, especially take its first breath, inflating its lungs and crying for twins. In such cases, the twins will be carefully monitored for the first time. In addition to assessing the Umbilical throughout labor by electronic fetal monitoring. Usually, the first baby’s condition and physical appearance, the cord twin is monitored via an electrode attached to its scalp while the midwife will weigh the baby and measure the

second twin is monitored by sensors strapped to the mother’s head circumference. The baby is dried and I THE BIRTH abdomen. Obstetricians, midwives, pediatricians, and an anesthetist wrapped to keep it from losing too much body will be close by in case any problems develop. Also, an epidural heat. A vitamin K supplement, which helps with anesthetic may be given so that the mother is ready if it does blood clotting, will be offered for the baby. become necessary to perform a cesarean section. APGAR SCORE

DELIVERY OF TWINS The Apgar score is a method of rapidly assessing the Pubic The most common position condition of a baby after birth to see if emergency care bone for twins is both head-down, is required. It is done at both one and five minutes after so it may be possible to birth. In dark-skinned babies, “color” refers to the mouth, deliver first one twin then palms of the hands, and soles of the feet. Compressed the other. The second twin bladder continues to be carefully monitored while the first SIGN SCORE: 0 SCORE: 1 SCORE: 2 twin is delivered. Heart rate None Below 100 Above 100 beats per beats per minute minute

Breathing None Irregular; Regular; Emerging head rate weak cry strong cry The ﬁrst twin is seen here being born in Muscle tone Limp Moderate Active the usual way, bending of head-ﬁrst. movements limbs

Reﬂex None Moderate Crying or response reaction or intense Dilated cervix grimace grimace The cervix is fully dilated to allow the ﬁrst then Color Pale or blue Pink, with blue Pink the second twin to hands and feet pass through.

Epidural and spinal blocks Nonpharmacological relief

In these forms of anesthesia, a local anesthetic is injected around the Nondrug options for pain relief include breathing techniques (see spinal cord in the lower back, which blocks feeling below the level of below), reflexology, acupuncture, hypnotherapy, relaxation techniques, the injection. However, as well as numbing pain in the abdomen, they water immersion (see p.198), and massage. Transcutaneous electrical may also make it difficult to move the legs. An epidural takes 20–30 nerve stimulation (TENS) uses tiny electric currents to stimulate the minutes to work, whereas a spinal anesthetic starts to work almost release of endorphins, the body’s own natural painkillers. immediately after it has been given. Deep, even Deep, even LATE FIRST STAGE breaths Light breaths breaths IN Epidural space This stage involves taking deep, even breaths at Spinal cord the start and end of a contraction, and light Cerebrospinal breaths during its peak. OUT fluid Short Short Short TRANSITION STAGE breaths breaths breaths To avoid pushing too IN early, the mother should alternate between taking short breaths and blowing out, and exhale gently OUT Lumbar when the contraction ends. Blow Blow Gently vertebra out Vertebra Tip of Deep, even Even catheter SECOND STAGE breaths breaths INSERTING A CATHETER The mother should take and IN For an epidural, a catheter is inserted between the hold a deep breath while Push Push dura (the outer membrane covering the spinal cord) pushing down smoothly. LOCATION OF and the spinal column. Spinal anesthesia is injected After a push, deep, even INSERTION POINT through the dura into the fluid around the cord. breaths should be taken. OUT

197 ALTERNATIVE BIRTHS Women have a number of options for delivery, including where and how to have the baby. Personal preference, well-being, and the baby’s safety are key factors involved in the decision.

WATER BIRTHS Giving birth in water can provide beneﬁts in terms of pain relief, as well as aiding relaxation.

ALTERNATIVE BIRTHS I ALTERNATIVE LABOR AND BIRTH The buoyancy of the water also makes a woman feel lighter and more able to move around. Water births may provide a less traumatic delivery for babies because they leave the ﬂuid of the uterus to enter the waters of the pool. Birthing pools may be available in the hospital prenatal unit or rented for use at home. Not all hospitals have birthing pools, and most have only one.

BIRTHING POOL Many hospitals now have birthing pools. They can be used during the ﬁrst stage of labor to help ease the contractions. The woman is then usually taken to a delivery room but can give birth in the pool.

HOME BIRTHS This option is suitable for women who have had previous normal pregnancies and deliveries and who have no medical problems. It is generally recommended that ﬁrst deliveries take place in a hospital. The prenatal care for a woman hoping for a home birth is provided by community midwives, who also perform the delivery. A hospital prenatal unit should be easily accessible in case of unforeseen complications during labor.

1.2 KEY TOTAL 1.0 BIRTHS OUT OF THE HOSPITAL 0.8 HOME BIRTH 0.6 BIRTHING CENTER 0.4

0.2 PERCENTAGE OF TOTAL BIRTHS (%) BIRTHS OF TOTAL PERCENTAGE 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 TIME (YEARS) OUT-OF-HOSPITAL BIRTHS Home and birthing-center births make up a small percentage of total births. A birthing center is a midwife-led maternity unit offering a homey approach. This graph, constructed from US data, shows declining numbers of out-of-hospital births since 1990. 198 GIVING BIRTH IN WATER Within seconds of the delivery, the baby is carefully lifted out of the water by the birth attendant to allow breathing to begin. During the brief time underwater the baby’s airway is closed so water is not inhaled with the ﬁrst breath. AFTER THE BIRTH Within seconds of delivery, a series of events occurs, beginning with the baby taking its ﬁrst breath. The umbilical cord is clamped and cut soon afterward, and the baby can then begin to feed without being directly connected to the mother.

DELIVERY OF THE PLACENTA DETACHING THE PLACENTA Helped by small contractions that Soon after the baby has been delivered and the Fundus of uterus Placenta starts Cord traction The top end to separate Cord may be pulled continue after the baby is born, the cord cut, the placenta must be removed. This is (fundus) of the At 5–15 minutes after steadily, in time placenta starts to peel away from the uterus gradually delivery, the placenta with contractions, wall of the uterus. Bleeding behind known as the third stage of labor. After the lowers, and the starts to detach from to remove the the placenta causes a clot to form, delivery, and once the uterus has contracted, the placenta detaches. the uterine wall. placenta quickly. which helps it detach further. midwife or physician may gently pull on the cord and ease the placenta out with one hand LABOR AND BIRTH I AFTER THE BIRTH LABOR AND BIRTH while placing the other hand on the lower abdomen to keep the uterus in place. An injection of oxytocine may be given to the mother after the baby’s head is delivered to help the uterus contract rapidly. The placenta must be carefully checked because any pieces of retained tissue may cause prolonged bleeding and prevent the Birth canal Although returning uterus from contracting fully. to its normal size, the passage is still large enough to Umbilical cord allow the placenta An uncut umbilical to pass through. cord will pulsate for up to 3 minutes

Network of vessels Multiple tiny blood vessels radiate from the umbilical cord

A HEALTHY PLACENTA The placenta usually weighs about 1 lb (500 g) and is 8–10 in (20–25 cm) in diameter. In Umbilical cord addition to the placenta, the Controlled traction on membranes need to be the cord, by a midwife removed from the uterus to or doctor, may be avoid the risk of serious needed to assist bleeding and infection. placental removal.

CUTTING THE CORD Umbilical vein The umbilical cord has been the baby’s lifeline Umbilical artery throughout the 40 weeks of pregnancy. The baby has been dependent on this collection of blood vessels for intake of oxygen and nutrients and removal of wastes. Soon after delivery, the cord is cut because the baby can now live independently of the mother. It may be advantageous for the cord to remain connected momentarily so blood in the placenta can pass into CLAMPING the baby’s circulation to boost AND CUTTING the blood volume. This takes Two clamps are placed around the cord about INSIDE THE CORD up to 3 minutes and allows 1 1 /2 in (4 cm) apart, and The umbilical cord contains one the baby to be placed on the the cut is made in the vein, which carries oxygen- and mother’s abdomen—with the middle of them. This nutrient-rich blood from the prevents leakage of mother to the fetus, and two cord intact—for a short time blood from either the arteries, which carry fetal waste without any problems. baby or the placenta. products to the mother. 200 AFTER THE BIRTHAFTER CIRCULATION IN THE FETUS CIRCULATION AT BIRTH The fetus cannot use its lungs until birth; before then they are deﬂated. From the baby’s ﬁrst breath, the circulatory set-up changes so In the uterus, it receives oxygen from maternal blood, which is that blood travels from the right side of the heart to the lungs for transferred into the fetal blood in the placenta. Most of the fetal blood oxygen and then back to the left side of the heart, from where it is directed from one side of the heart to the other, via a small opening passes into the aorta. The ductus arteriosus, ductus venosus, and called the foramen ovale. A vessel called the ductus arteriosus allows the umbilical vessels close and become ligaments. The foramen blood to enter the aorta without having to pass through the lungs. ovale is also forced shut by the pressure of the blood returning AND BIRTH I LABOR The blood leaves the heart via the aorta to supply the fetal body. to the left atrium (after collecting oxygen from the lungs).

Blood supply Blood supply Blood supply Ductus from upper to upper from upper arteriosus body body Aorta body closes Forms branches that distribute blood Increased Right atrium around the body Pulmonary artery blood ﬂow to the lungs Foramen ovale Lung Pulmonary Small opening that veins More allows oxygen-rich Ductus arteriosus oxygen–rich blood from the Allows blood from blood enters umbilical vein to the pulmonary left atrium travel from the artery to enter Right atrium than in fetal right atrium to the the aorta without circulation left atrium having to pass Pulmonary through the lungs Foramen artery ovale closes Left atrium Left atrium Ductus venosus Connects the Heart umbilical vein to Heart Liver the inferior Descending aorta vena cava

Umbilical vein Carries nutrients Inferior vena cava and oxygenated Inferior Descending blood from the vena cava aorta placenta Umbilical arteries Placenta Carry blood that Forms the contains waste interface between products away maternal and from the fetus fetal circulations

FETAL NEWBORN CIRCULATION CIRCULATION The newborn circulation must set to Much of the blood work immediately after birth to ensure delivered to the fetal the baby receives oxygen. There is no mixing of blood in the newborn organs and tissues is a Blood supply Blood supply combination of oxygen-rich and to lower body circulation, so the vessels contain to lower body oxygen-poor. The vessels carrying mixed either oxygen-rich blood (shown in red) blood are shown in purple here. or oxygen-poor blood (shown in blue).

SUCKLING REFLEX This is a primitive reflex that is present HORMONE CHANGES AFTER BIRTH from birth and is closely linked to the rooting reflex (see p.210). Gently The levels of estrogen, progesterone, and other hormones fall dramatically following the birth of a baby. Effects of the drop include shrinkage of the uterus touching the roof of a baby’s mouth and increased tone in the pelvic floor muscles. The mother’s circulating blood triggers the suckling reflex. For this to volume—raised to meet the demands of the fetus—returns to normal. happen, the baby needs to take a KEY nipple (or bottle teat) into the mouth. ESTROGEN Many newborn babies are put to the PROGESTERONE PLUMMETING hCG LEVELS breast soon after birth and can feed The rapid fall in the right away. However, for others it will levels of estrogen and take time and patience to encourage progesterone is BLOOD LEVELS BLOOD thought to play a role a baby to suckle effectively. Suckling in the baby blues. It is FIRST FEEDING the nipple stimulates the production of not known why some A rich, creamy substance called women are more oxytocin and prolactin, the hormones 04 8121620242832364044 colostrum, packed with antibodies, susceptible to the is released for the first few days. that are needed for the production GESTATIONAL WEEKS Delivery sudden drop. True breast milk then starts to flow. and release of milk. 201 ASSISTED BIRTH Situations in which help may be needed to deliver a baby include being overdue, slow progress during labor, fetal distress, or an abnormal lie. Assisted deliveries may be planned or are required urgently if problems arise before or during labor. LABOR AND BIRTH

INDUCING LABOR Amniotic ﬂuid Long, thin Induction of labor may be recommended if a surgical pregnancy goes beyond 42 weeks, if labor fails hook to start after the water has broken, and with certain medical conditions, such as preeclampsia. Sweeping the membranes, in which the membranes are gently pulled away from the cervix, may be performed during a vaginal examination. Another method is to insert prostaglandin into the vagina. If these methods fail, pitocin (synthetic oxytocin) in a drip may help increase contractions. Amniotic Mucus plug membrane OXYTOCIN CRYSTALS Enema This light micrograph shows the structure INSERTION OF PROSTAGLANDIN RUPTURE OF MEMBRANES of oxytocin, a hormone that is released Prostaglandin is used to induce labor and is inserted A hook is passed through the vagina to tear the by the pituitary gland. One of its main into the vagina close to the cervix as an enema or amniotic membranes, allowing the ﬂuid to drain out. functions is to instigate labor, but on a thin strip of gauze. The hormonelike substance This method tends to be used if labor is progressing it is not known what triggers its release. helps ripen the cervix and stimulate contractions. slowly rather than if it has not started at all.

Tube to Spoon-shaped Suction suction DELIVERY BY FORCEPS forceps cup pump AND VACUUM Forceps or vacuum deliveries are used in about 5–15 percent of births, for a number of reasons, but most commonly, for fetal distress (usually indicated by the fetal heart rate) and maternal exhaustion after a labor of many hours. Either one of these methods may be used to help the delivery of a baby when it is low in the pelvis, but the cervix must be fully dilated so that the baby can pass through. Forceps are similar to large salad servers, which come apart in two pieces but lock to avoid crushing the baby’s head during delivery. DELIVERY BY FORCEPS The ends are curved to cradle the baby’s head. The The two blades of the forceps are placed DELIVERY BY VACUUM EXTRACTION vacuum (also known as the silastic) extractor has a around the baby’s head and locked together. The cup is placed on the baby’s head, and The physician pulls the forceps while the suction is then applied to ﬁx it securely. The suction cup, which is attached to the baby’s head. mother pushes with each contraction. device is pulled gently to help the baby out. An episiotomy is necessary with a forceps delivery, but may not be needed for a vacuum extraction.

EPISIOTOMY Temporary ring An episiotomy is a cut made in the INCISION SITES from suction cup tissues between the vagina and An episiotomy may be made anus to create a bigger opening either straight back from the vaginal opening toward the and prevent tissue damage. It is anus or to one side at an angle. SILASTIC MARKS carried out to prevent a bad tear The suction received or if there is fetal distress and the Vagina through the cup on the baby needs to be delivered quickly. Mediolateral incision top of the baby’s head The procedure is done under local, can leave a red circular epidural, or spinal anesthesia. The Median incision bruise, known as a cut is sewn up afterward. Anus chignon. Although it looks alarming, the mark only lasts a week or so. 202 ASSISTED BIRTH CESAREAN SECTION In a cesarean section, the baby is removed from the uterus through an incision in the abdominal wall. There are a number of reasons why the vaginal route becomes impossible or undesirable. A cesarean may be planned, due to a nonurgent reason, for example

if the mother is carrying twins, or it may be unplanned, due to an AND BIRTH I LABOR urgent reason, such as the development of fetal distress, or a less urgent one, such as no progress in labor. Before the LOW TRANSVERSE INCISION CLASSICAL INCISION operation, the abdomen is TYPES OF INCISION numbed, either by a regional The most common type of incision anesthetic (epidural or spinal), into the uterus is the low transverse which leaves the mother aware, incision. In some cases, a larger vertical cut (classical incision) may be made, or by general anesthesia, with for example if the baby lies across the the mother unconscious. abdomen. A low vertical incision may be used for other types of abnormal BREECH PRESENTATION lie. The initial incision in the abdominal This X-ray shows a fetus in a breech lie wall is usually the same in each case. (where the head is not the presenting part). KEY If the baby cannot be manipulated, before INCISION IN ABDOMINAL WALL labor, into a head-ﬁrst position, a cesarean INCISION IN UTERUS is the safest delivery option. LOW VERTICAL INCISION

HOW THE PROCEDURE IS PERFORMED A cut is made through the skin of the abdomen and the layers of tissue and muscle beneath are parted to reveal the uterus. The uterus is opened up, following one of the incision lines (top right), and the baby is lifted out. Cutting through the Placenta Umbilical Uterine 1 abdominal and uterine walls cord cavity After making a 4–6 in (10–15 cm) cut in the abdomen, the surgeon works through the muscle and Uterine fat layers until the uterus is felt. wall A small cut is made in the wall, which is widened Abdominal by hand until the hole wall is big enough to Inserting surgical retractor deliver the baby. 2 This metal instrument is hooked around the edge of the abdominal wound and pulled gently back. This ensures the surgeon has a clear view of the internal organs and tissues.

Delivering the baby 3 The baby is gently lifted out through the openings in the Surgical uterine and abdominal walls and retractor passed to the pediatrician or midwife. The baby is handed to the mother as soon as possible.

Pubic bone

Compressed bladder

Cervix

Vagina 203 THE SPECIAL FEATURES A FETUS DEVELOPS TO COEXIST WITH THE MOTHER DURING PREGNANCY CHANGE SOON AFTER BIRTH TO ENABLE THE BABY TO LIVE INDEPENDENTLY. A NEWBORN BABY ACQUIRES SKILLS VERY QUICKLY, IN RESPONSE TO THE MANY STIMULI SURROUNDING IT. THESE ACCOMPLISHMENTS EVOLVE IN A RECOGNIZED PATTERN, WITH THE FIRST DEVELOPMENTAL BUILDING BLOCKS LAID DOWN WITHIN DAYS OF BIRTH. THE KEY SKILLS A BABY ACQUIRES ARE KNOWN AS THE DEVELOPMENTAL MILESTONES. THESE, ALONG WITH OTHER FACTORS SUCH AS WEIGHT AND HEAD CIRCUMFERENCE, ARE CAREFULLY NOTED BY HEALTHCARE PROFESSIONALS AND SEEN AS A MEASURE OF GOOD HEALTH AND WELL-BEING. POSTNATAL DEVELOPMENT RECOVERY AND FEEDING The weeks after birth bring great emotional and physical changes for the mother, not least the onset of feeding. Hormonal changes, the responsibilities of becoming a parent, and a severe lack of sleep all add to the impact. RECOVERY AND FEEDING I RECOVERY THE RECOVERING MOTHER The few ﬁrst weeks with a new baby are wonderful but exhausting, especially as the mother undergoes various physical changes. The enlarged uterus and loose abdominal muscles can make the abdomen continue to appear pregnant, and there may be cramping, similar to contractions, as the uterus shrinks. Bleeding occurs for the ﬁrst two to six weeks; the discharge is initially bright red, turning to pink and then brown. An episiotomy scar (see p.202) will be sore initially, and urinating may be uncomfortable. Constipation is also a common problem. During the early days of breastfeeding, the breasts can be sore and

POSTNATAL DEVELOPMENT DEVELOPMENT POSTNATAL engorged; any nipple tenderness will improve if the baby latches on well (see below). All these problems should be resolved with time.

Enlarged uterus Uterus size immediately after delivery SHRINKING UTERUS By six weeks after the birth, the uterus has Normal size almost returned to its Uterus size about size before pregnancy. 6 weeks post-birth BONDING THROUGH FEEDING Breastfeeding can help Skin-to-skin contact is a special part of the bonding process between with this process due Cervix mother and baby. Breastfeeding offers to the production of Cervix does not regain oxytocin (see opposite), predelivery tightness many health beneﬁts to both, as well which stimulates as a quiet period of time together. muscle contractions.

KEGEL EXERCISES EMOTIONS Most women find they experience a wide Strengthening the pelvic floor—the slinglike muscles that support the bladder, bowel, and uterus (see p.91) range of emotions in the days following —is as important after birth as it is during pregnancy. the birth of a baby—from absolute elation It can help with bladder control and make urine leakage to feeling down and tearful. The ups and less likely to occur. The muscles can be located by downs experienced are understandable imagining trying to stop the flow when urinating. The muscles can be squeezed repeatedly, several times a day, given the great hormonal changes that either pulsing or holding for several seconds. These have taken place and the sleep deprivation exercises should be built up over time. that is almost universal when parenting a newborn baby. Feelings of exhilaration and achievement are common following the delivery, but these may soon give way to sadness. The so-called baby blues are common and usually resolve with time. However, if the feelings of sadness and not coping persist, postpartum depression may be the cause, and this requires specialist help (see p.243). EXERCISING WITH YOUR BABY Kegel exercises can be incorporated into a daily routine, BONDING perhaps when the baby is sleeping. A few minutes spent Getting the father involved early is important, not just strengthening these muscles will pay dividends later. to ease physical and emotional pressure on the mother, but also so he can develop his own bond with the baby. 206 RECOVERY AND FEEDING BREASTFEEDING Breast milk is often considered to be the ideal food for a baby because it contains all the nutrients needed for early growth and development, and also provides antibodies that help fight many diseases, such as gastroenteritis and pneumonia. This lowers the risk of illness during the first year of life. Production and release of breast milk rely on two hormones that are produced by the pituitary gland in the brain: prolactin I POSTNATAL DEVELOPMENT stimulates milk production; and oxytocin initiates milk ejection or “let down.” Hypothalamus Initially, the breasts produce Pituitary gland a thick substance called

colostrum (see below), which BRAIN is then superseded by the mature milk after a couple Milk production Prolactin produced by the pituitary gland of days. At each feeding, stimulates the secretory lobules in the both breasts produce breasts to produce milk thirst-quenching “foremilk” followed by nutrient- rich “hindmilk.” Milk release The pituitary gland also releases oxytocin, which contracts the smooth muscle of the secretory lobules, forcing milk into the lactiferous ducts to the nipple KEY PROLACTIN RELEASE

OXYTOCIN RELEASE

THE LETDOWN REFLEX Secretory The squeezing of milk out of the lobule breast is stimulated by oxytocin. There may be temporary pain or tingling. At ﬁrst, let down is triggered by suckling, but once breastfeeding is established other triggers, such as hearing the baby Lactiferous cry, can cause hormone release. BREAST STRUCTURE ducts

LATCHING ON Latching on occurs when a baby correctly positions its mouth on the breast and can suckle effectively. This does not always happen naturally and can be Energy Energy painful if done incorrectly. The breast should be well inside the mouth with Lactose 55 kcal Sodium Lactose 67 kcal Sodium the nipple near the back and most of the areola (the dark area around the 5.3g 48mg 7.0g 15mg nipple) also in the mouth. The baby moves its jaw up and down, and tongue Fat Calcium Fat Calcium movements cause release of milk. This position avoids the nipple being pulled 2.9g 28mg 4.2g 30mg or pinched and becoming sore, and maximizes the amount of milk taken in. Protein Vitamins Protein Vitamins 2.0g 189mmg 1.1g 134mmg COLOSTRUM BREAST MILK (100ML) (100ML) THE CHANGING COMPOSITION OF BREAST MILK Colostrum and breast milk differ in their composition. Also known as “ﬁrst milk,” colostrum is rich in the antibodies that help the baby’s immature immune system ﬁght infection. Colostrum is also very rich in vitamins.

BOTTLE FEEDING

Not all mothers want to breastfeed and some are unable to for health or other reasons. Formula is intended to replicate breast milk as closely as possible: it is made from cows’ milk that is fortiﬁed with extra minerals and vitamins. It is important that a mother is not made to feel guilty if she feeds STIMULATING THE REFLEX CORRECT POSITION her baby formula. Bottle feeding still gives the opportunity for bonding while Brushing the baby’s lip against the Once the mouth opens to 1 2 providing the key nutrients a new baby needs. It also allows the father to nipple encourages the mouth its widest, insert the nipple and to open and accept the nipple. The areola, positioning them deep spend extra time with the baby and to give feedings during the night, allowing baby’s head can be cradled in the in the mouth, while continuing the mother more opportunity for sleep without the need to express milk. hand and guided into position. to support the baby’s head. 207 THE NEWBORN BABY A healthy newborn baby has the same complement of organs and tissues Wrist as an adult, but these change and mature as it develops. Over the ﬁrst six The carpal bones of the wrist are largely made weeks of life, the baby’s appearance will begin to change. up of cartilage.

ANATOMY EARLY BODY STRUCTURE

I THE NEWBORN BABY 3 The relative size and A new baby weighs on average 7 /4 lb (3.5 kg). Although well composition of a baby’s prepared for the world outside, a baby’s organs and tissues anatomy change with will continue to change and develop until adulthood. Some time. Bodily structures are monitored during the early are relatively large in the newborn, reflecting the crucial roles weeks to check that the baby they play during pregnancy and early childhood. For example, is developing normally. Heart the large thymus gland in the chest is vital for developing Blood pumps early immunity; later in childhood, when it is no longer from the heart to the lungs for needed, it starts to shrink. Changes in the circulation Jaw Lungs the first time. Fully formed teeth The first breath draws take place at birth, triggered by the baby’s first are present within air into the lungs and breath, which causes the lungs to start the jawbone. enables them to function. Eye POSTNATAL DEVELOPMENT DEVELOPMENT POSTNATAL working and allows the baby to breathe Frontal socket Trachea independently (see p.201). Some features bone of a newborn’s appearance, such as a conical-shaped head, reflect what has happened during the birth and will resolve with time.

EYES A newborn’s eyelids tend to look puffy as a result of pressure in the birth canal. Early vision is poor, and the eyes can appear crossed due to underdeveloped muscles.

Anterior fontanelle

Parietal bone Ear SKULL AND BRAIN Neck Undeveloped The skull is made up of bony plates, muscles cannot which meet at seams (sutures), and support the large, two soft spots called fontanelles. These heavy head in the allow the bones to slide over each ﬁrst few weeks. other so that the skull can change shape as it moves through the birth Posterior fontanelle Occipital bone Thymus gland canal. This accounts for the temporary Oversized at birth, this gland cone-shaped appearance of some plays a key role in developing a Cerebral functioning immune system. newborn heads. Later, the fontanelles hemispheres will close: the back (posterior) one Ribcage by about six weeks and the front (anterior) one by 18 months. Developing neural networks NEURAL DEVELOPMENT Fingernails This CT scan of a newborn baby’s brain A newborn’s nails shows large areas of developing neural Fluid-ﬁlled brain grow quickly and networks (green). Multiple connections ventricles can be sharp. between the nerve cells of the brain are laid down from the moment of birth. 208 TEMPERATURE CONTROL Newborn babies do not have a fully developed ability to regulate body temperature. Because of the large surface area POSTNATAL CHECK-UPS of the skin relative to body weight, a new baby loses heat Every baby is checked soon after birth and then again easily and cannot shiver to about six weeks later. This provides an opportunity for generate body temperature. the external anatomy, such as the hands and feet, to be Babies can cool down by checked as well as the heart, lungs, hips, and other internal sweating and through the structures. The physician checks the roof of the mouth dilation of blood vessels in for a cleft palate and shines a light in the eyes, as well as the skin. Their ability to lose carefully listening to the chest. The back is examined to heat is not as effective as look for signs of spinal problems, and the legs are moved LISTENING TO THE HEART an adult’s so a baby must around to assess the stability of the hips. The scrotum is not be allowed to overheat. The physician checks for unusual heart checked in boys to make sure both testes are present. The sounds, known as murmurs. These may doctor will also look for any birthmarks on the skin. be normal or may indicate a problem. SWADDLING This is a technique of wrapping up a baby to create a sense of security while making sure to avoid overheating.

Liver Relatively large at birth, the liver is the site of new blood- cell formation in the fetus.

Small Large Rectum Stomach intestine intestine

GENITALS AND BREAST TISSUE In both boys and girls, the genitals may appear enlarged, swollen, and dark in color due to the high levels of female hormones in the mother before delivery. These hormones pass from mother to baby across the placenta. One or Genitals both breasts may be enlarged, and a small amount of ﬂuid Feet Newborn babies may leak from the nipple soon after birth. Girls may also often lie with have a vaginal discharge that sometimes contains their feet turned a small amount of blood. outward.

Pelvis

Gallbladder Appendix

Hip If the femur does not sit securely in the pelvic socket, the hips may be unstable. Bones Some bones will fuse as they mature. UMBILICAL CORD FLAKING SKIN A plastic clip is left on the cut cord Cartilage A newborn baby’s skin can appear flaky, until it dries and seals, stemming all Cartilage at the ends of long and this may persist for a few days or even blood flow (see p.200). The stump bones enables bones to lengthen, weeks. Postmature babies may also have blackens and falls off within 10 days. before gradually ossifying. slightly dry and wrinkly skin. 209 52 HEAD CIRCUMFERENCE Top centile 50 EARLY RESPONSES Measurements are taken 48 from the widest part of the skull. AND PROGRESS 46 44 On average, a baby spends more than half the day 42 Middle centile asleep. Despite this apparent inactivity, the first 40 Lowest Corresponds to 38 centile average head size (or weeks of life are extremely eventful—growth is length or weight) rapid, and skills are acquired on a daily basis. (CM) HEAD CIRCUMFERENCE 36 34 POSTNATAL DEVELOPMENT POSTNATAL 32 GROWTH 76543210 8 9 10 11 12 13 14 15 16 17 18 19 222120 23 A baby grows at an incredible rate during the early weeks AGE (MONTHS) and months, while at the same time, organs are developing and 96 92 BODY LENGTH maturing. This rapid growth needs to be fueled by frequent Small babies are measured lying feedings and it also relies on periods of inactivity, when the baby 88 down—once they are able to stand, height is measured. is sleeping. Growth and weight are carefully monitored because 84 they are key indicators of health and development. 80 Percentile charts are widely used to record 76 changes in size over time. If measurements 72 are plotted regularly they will show whether 68 a child falls within the average range and if LENGTH (CM) LENGTH 64 growth is occurring at a steady rate. Growth 60 that tails off may indicate that there is an underlying health problem. 56 52 48 Wrist bones KEY 44 take 2 years 99.6TH CENTILE 76543210 8 9 10 11 12 13 14 15 16 17 18 19 222120 23 to ossify AGE (MONTHS) 75TH CENTILE 50TH CENTILE 13 Skeletal 25TH CENTILE 12 BODY WEIGHT gaps show 0.4TH CENTILE 11 Weight is a key indicator of unformed 10 health, although it tends to bone FULL CENTILE RANGE 9 fluctuate in the first few 8 days of life. DEVELOPING GROWTH CHARTS 7 BONES Measurements that fall 6 Cartilage panels at between the top and WEIGHT (KG) 5 the ends of long lowest centiles are 4 bones enable their considered average. 3 hard bone centers These charts show rates 2 to grow as the child of growth for girls— 1 ages. These will separate charts are used 0 gradually turn into for boys, who grow 01234 56789101112 bone tissue (ossify). at different speeds. AGE (WEEKS)

STEPPING REFLEX PRIMITIVE REFLEXES If held upright on a firm surface, a Various reflex reactions in response to specific stimuli are expected baby will take steps as if walking. to appear and then disappear at particular stages in infant This is present for the first six weeks. development. Their presence is an indicator that the neurological system is functioning and developing well. Physicians look for GRASP REFLEX these reflexes at routine early checkups, and often they can be For about the first three months, a observed in a baby’s daily activities. The rooting reflex is used to baby will close its latch a baby onto the nipple when feeding (see p.205). hand into a fist if an object is placed in the palm.

STARTLE REFLEX A baby will ﬂing out ROOTING REFLEX its arms in shock if If a baby is touched its head suddenly near the mouth, falls back. Present its head will turn to for three months, the stimulus. This this is also called usually disappears the Moro reﬂex. by four months. 210 EARLY RESPONSES AND PROGRESS SLEEPING AND WAKING A baby’s day is punctuated by frequent naps—on average six or seven a THE EFFECTS OF MELATONIN day in the newborn—and periods of wakefulness, when he or she becomes increasingly responsive. Because of their small stomachs and an almost This hormone, secreted by the pineal gland in the brain, regulates constant need for food, babies usually wake up every two to four hours. It can other hormones and helps maintain be one or two years—or for a small number, even longer—before a baby sleeps the body’s sleep–wake rhythm. consistently through the night. High levels of melatonin are However, by about six weeks a associated with an increased need to sleep. Maternal baby’s 24-hour clock is established melatonin passes and longer periods of sleep can to the fetus via the Pineal take place during the night. placenta, and to a gland newborn baby via breast milk. Raised

levels of melatonin I POSTNATAL DEVELOPMENT SLEEP DEVELOPMENT Within a few weeks, a baby may sleep are believed to help LOCATION OF for up to ﬁve hours at a time, reﬂecting a baby sleep. PINEAL GLAND the gradual increase in stomach size.

25 minutes 25 minutes awake asleep

“ACTIVE SLEEP” (REM) “QUIET SLEEP” (NON-REM) This stage of sleep involves high brain Quiet sleep has two key stages: activity, which is believed to aid nerve-tissue light and deep sleep. Babies pass

development. Newborns spend 50 percent from light to deep sleep and back BABY

of their sleeping hours in REM sleep, double again, before moving into REM. NEWBORN the amount in adults. During active sleep, the baby’s eyes move rapidly back and forth, 6PM MIDNIGHT 6AM NOON 6PM Light sleep and the baby is restless and easily awakened. asleep Brain activity slows as the baby falls awake asleep. The baby may be twitchy and respond to light and noise.

THE SLEEP–WAKE CYCLE AWAKENS ADULT A newborn has a roughly During the transition from deep sleep back 50-minute sleep cycle, Deep sleep to light sleep, the baby 6PM MIDNIGHT 6AM NOON 6PM made up of quiet and Brain activity is at its lowest. The baby active sleep. This latter is most liable to wake AMOUNTS OF SLEEP up and break the cycle. is quiet, motionless, and at the most stage is when signiﬁcant difﬁcult stage to rouse. A newborn baby spends on average 16 hours asleep nerve development is each day (this can range from 12 to 20 hours). The thought to occur. average adult requires half this amount of sleep.

EARLY COMMUNICATION THE SENSES Babies communicate with other people Babies are highly responsive to sound from birth, from birth—indeed their very survival as demonstrated by the way a new baby is startled depends on their ability to express their by loud noises and within a few weeks starts to needs—and they do this in a variety of turn toward voices. Parents are offered a screening ways, primarily through crying. Babies audio test for their baby within a few weeks of instinctively cry to show hunger, distress, birth. Vision, however, is thought to be relatively discomfort, pain, and also loneliness, and poorly developed at birth, newborn babies seeing mothers become ﬁnely tuned to the best at a distance of about sound of their own baby’s cry and 8–10 in (20–25 cm). what it means. A combination of CONTRASTING PATTERNS other sounds develop after about Poor vision means that young babies respond most to primary EXPRESSING FEELINGS two weeks: ﬁrst squealing; then gurgling contrasting colors, or black and It is possible to recognize a baby’s needs by and cooing. Parents quickly come to have white, and geometric shapes. the nature of its crying. A different cry is used to denote pain from hunger, and this forms a an understanding of their babies’ feelings language to which parents become attuned. without a word ever being spoken.

FIRST SMILES The timing of the first genuine smile can vary, GENUINE but most babies are thought to smile for the first RESPONSE time after about four to six weeks. This is usually A baby’s first true smile is an amazing AUDIO TESTING in response to the sight of their parents’ faces or event, involving a If the basic audio test detects the sound of their voices. Before this, babies can reflex response from a problem, this more complex pull facial expressions that resemble smiles but both the eyes as well test gauges a baby’s response are often in response to wind or fatigue. as the mouth. to clicks through headphones. 211 THE FIRST TWO YEARS The early part of a child’s life is a time of remarkable physical

and developmental change. The complex nerve networks in the 1 brain enable great achievements, such as sitting, standing, first steps, and first words. Even at this early stage, a child is clearly 1 an individual, able to communicate needs and wishes. ⁄4 THE FIRST TWO YEARS I THE FIRST PHYSICAL CHANGES CHANGING PROPORTIONS In addition to the reduction in head size relative to the rest of the 1 At birth, the head ⁄2 body (see right), the first two years see a child’s appearance change is as wide as the in other ways—the limbs and trunk lose some of their baby fat, shoulders and

makes up about HEIGHT BODY OF TOTAL PROPORTION reﬂecting increased movement and growth, the hair thickens and one-quarter of 1 grows, and the face takes on a more mature appearance. This is a body length; by ⁄4 two years, head size result of the eruption of many of the milk teeth and the loss of has reduced relative some of the subcutaneous fat around the cheeks and chin. to body size. AT BIRTH 2 YEARS ADULT

TEETHING Central incisor POSTNATAL DEVELOPMENT DEVELOPMENT POSTNATAL Milk teeth usually ﬁrst emerge APPEARANCE OF APPEARANCE OF Lateral incisor at six to eight months and continue UPPER TEETH LOWER TEETH erupting until almost three years. Canine UPPER Adult teeth begin to appear at TOOTH TIME OF TOOTH TIME OF TEETH ERUPTION ERUPTION about six years. Opinions vary First molar as to whether teething can cause Second molar Central incisor 8–12 months Central incisor 6–10 months symptoms, such as fever; many experts believe they just happen to occur together. However, Lateral incisor 9–13 months Lateral incisor 10–16 months teething may cause swollen gums, Second molar drooling, and sleep problems. Canine 16–22 months Canine 17–23 months First molar LOWER MILK TEETH TEETH Canine First molar 13–19 months First molar 14–18 months The milk teeth erupt through the gums in a recognized sequence, with the two Lateral incisor lower central incisors usually appearing Second molar25–33 months Second molar 23–31 months ﬁrst and then the upper central incisors. Central incisor

DEVELOPING BRAIN FUNCTION Gross motor Fine motor WEANING Thinking and movement movement Language The newborn brain is made up of billions of nerve cells reasoning Introducing solids into a baby’s diet (neurons) that send and receive messages along nerve while reducing milk intake is called fibres. Almost a complete set of neurons is present but Language weaning. Its timing varies, but the they have limited links. In the early years, multiple new general advice is that solids can be connections are formed, as the senses encounter new Emotional stimuli and the body responds. Brain development and social started from six months—before behavior this time, the digestive system is occurs at its fastest rate in the first six years of life, still developing. Many parents give during which time the brain almost reaches its full size. babies puréed or mashed foods 1,600 for a few weeks before introducing 1,400 finger food—small pieces of food that a baby will be able to pick up 1,200 Full size brain and eat. Breastmilk or formula 1,000 usually remains the main source 80 percent of reached at 18 of nutrients for the first year. 800 adult size of brain reached years old 600 at 2 years old 400 BRAIN WEIGHT (GRAMS) 200 FIRST SOLIDS 0 Simple purées of 0 5 10 15 20 25 vegetables and AGE (YEARS) REGIONS OF fruit are often the INCREASING BRAIN SIZE BRAIN CONTROL first foods. Finger The brain’s rapid development, as measured As in adults, a baby’s brain foods encourage by its weight, can be seen on this graph. At has specific areas that control a baby to feed birth, the brain weighs about 14 oz (400 g); its activities. The areas linked independently. by 2 years, it has reached 80 percent of to its core development are its final adult weight of 3 lbs (1,400 g). shown here. 212 THE FIRST YEARS TWO MOVEMENT AND COORDINATION LANGUAGE AND COMMUNICATION Holding up the head or controlling its side-to-side and back-to-front Babies use both verbal and nonverbal means to communicate movements is not possible for a newborn baby, so the head needs how they feel and what they need. Crying is an instinctive way support at all times. This need lessens after a few weeks, and gradually of communicating (see p.211), but the early gurglings of the first complete head control is achieved. This fundamental skill, along with few weeks gradually give way to articulated sounds as the baby the control of body posture, form the basis for all movement skills. gains awareness and experiments with its voice. Hand gestures, There is a specific sequence: a baby learns weight bearing and then such as pushing something balance. Many attempts are unwanted away, also become needed before independent a key means of communication. I POSTNATAL DEVELOPMENT walking is possible—it rarely At around six months, babbled starts before 10 months. conversations begin, and by Movements become more one year the baby should say complex as a range of recognizable words, such as actions are coordinated “mama” and “dada,” and enjoy at the same time. repeating familiar sounds.

INDEPENDENT MOVEMENT Crawling starts at around the age BABY SIGNING of seven months followed by From as young as six months, babies can walking with support. Some learn a simple sign language to convey what babies shufﬂe on their bottoms they want. In this image, a mother teaches as a ﬁrst means of getting around. her baby to sign for “more.”

DEVELOPMENTAL MILESTONES

The core skills that are achieved throughout early childhood are known as some children achieve particular milestones earlier or later, and some skills are developmental milestones. These can broadly be divided into three categories: skipped altogether. Developmental milestones form the basis for acquiring physical achievements; reasoning and communication skills; and emotional more complex abilities later. By the age of two years, children have gained development combined with social skills. The milestones usually occur in a an impressive degree of independence, and the ability to walk allows them to speciﬁc order and, for most children, within a certain age range. However, express the innate desire to explore the surrounding world.

AGE (MONTHS) 024681012141618202224

PHYSICAL ABILITIES • • • Control of posture, balance, • Lifts head and chest • Crawls • Walks unaided and movement are the vital • Brings hand to mouth • Walks holding furniture • Carries or pulls toys early motor skills. A baby Grasps objects with hands Bangs objects together Starts to run • Eats ﬁnger foods unaided • Can throw and kick a ball ﬁrst learns head control, • Walks up stairs unaided and eventually can sit. • Reaches for objects • Can hold and use a pencil Once neural connections • Rolls over • Crawls up stairs • Gains control of bowels for these skills are laid • Supports own weight on feet • Squats to pick up objects down, crawling, standing, • Sits unsupported • Jumps with both feet and walking are possible. • Stands by hoisting up own weight • Starts to drink from a cup

THINKING AND • • LANGUAGE SKILLS • Smiles at parents’ voices • Recognizes own name Points to named objects Successful communication • Starts to imitate sounds Responds to simple commands • Sorts shapes and colors • Uses ﬁrst words • relies on an understanding Says simple phrases • Imitates behavior • Follows simple instructions of language. Imitating • Engages in fantasy play sounds made by parents is the ﬁrst step toward • Begins to babble gaining language and higher • Investigates with hands and mouth skills such as thinking, • Reaches for out-of-reach objects • Says “dada” and “mama” to parents reasoning, and logic. • Understands “no,” “up” and “down” • Can put two words together

SOCIAL AND EMOTIONAL • • DEVELOPMENT • Makes eye contact • Cries when parent leaves Social interaction begins with Recognizes familiar people Shows preferences for people and objects • Cries when needing attention • Repeats sounds and gestures watching people and smiling. • Smiles at mother, then socially Play helps build social skills, • Watches faces intently so by one year most babies • Recognizes parents’ voices interact happily with others; • Imitates others’ behavior gaining independence and • Enjoys company of other children an understanding of social • Responds to own name • Demonstrates deﬁant behavior behavior are also key. • Plays peekaboo • Stays dry during the day

213 A WIDE RANGE OF CONDITIONS CAN AFFECT THE HUMAN REPRODUCTIVE SYSTEM. SOME MAY AFFECT FERTILITY, WHILE OTHERS ARE EXCLUSIVE TO PREGNANCY OR BIRTH. BABIES MAY ALSO HAVE A VARIETY OF MEDICAL CONDITIONS, SOME ARISING FROM PROBLEMS IN DEVELOPMENT DURING EARLY PREGNANCY, OTHERS RELATING TO EVENTS LATER IN PREGNANCY OR DURING BIRTH. BECAUSE OF THERAPEUTIC ADVANCES AND AN INCREASED UNDERSTANDING OF THE WAY IN WHICH CONDITIONS DEVELOP, MANY CAN BE TREATED SUCCESSFULLY, PRODUCING A HEALTHY OUTCOME FOR MOTHER AND BABY. FERTILITY TREATMENTS HAVE PERHAPS SEEN THE GREATEST IMPROVEMENTS, OFFERING HOPE TO THOUSANDS OF CHILDLESS COUPLES. DISORDERS FERTILITY DISORDERS INFERTILITY IS A COMMON PROBLEM, AFFECTING AS MANY AS 1 IN 10 COUPLES WHO WISH TO CONCEIVE. THE PROBLEM MAY LIE WITH EITHER THE MALE OR THE FEMALE PARTNER, OR THERE MAY BE A COMBINATION OF FACTORS INVOLVED. ASSISTED CONCEPTION TECHNIQUES NOW OFFER HOPE TO MANY INFERTILE COUPLES.

FEMALE FERTILITY DISORDERS In around half of all instances of couples experiencing fertility the sperm, and conditions that prevent the fertilized egg either problems, the problem lies with the woman. The underlying causes from implanting or growing in the uterus. Age is also a key factor in of infertility can be broadly divided into problems relating to egg women because fertility reaches its peak by the age of about 27 and production, egg transportation toward the uterus, the egg meeting then falls, gradually at ﬁrst, then more rapidly from the age of 35. FERTILITY DISORDERS I FERTILITY DISORDERS DAMAGED ABNORMALITIES FALLOPIAN TUBES OF THE UTERUS WHEN A FALLOPIAN TUBE IS DAMAGED, OFTEN AS A RESULT PROBLEMS WITHIN THE UTERUS CAN PREVENT OF AN INFECTION, THE MONTHLY JOURNEY OF AN EGG TO A FERTILIZED EGG FROM EITHER IMPLANTING THE UTERUS MAY BE PREVENTED. OR DEVELOPING NORMALLY . One or both tubes may be damaged due to an infection The lining of the uterus may be damaged by an of the pelvic organs (see p.218). Endometriosis (see infection, or hormonal factors may result in a failure to p.218) may also affect the fallopian tubes. Tubes prepare the lining for pregnancy during the menstrual may be assessed by keyhole surgery (laparoscopy) or cycle. Fibroids (see p.219) or an abnormally shaped hysterosalpingography, in which dye is injected through uterus (see p.221) may prevent normal fetal growth. the cervix and its progress through the uterus and tubes is Hysteroscopy (in which a viewing instrument is passed BLOCKAGE IN A FALLOPIAN TUBE tracked on X-rays. Microsurgery may be suitable for some This hysterosalpingogram reveals that the right into the uterus via the cervix) or an ultrasound scan tubal damage, or drug treatment in cases of endometriosis. tube (on the left, as shown) is blocked next to the may be used to check the uterus. Causes are treated if Otherwise, assisted conception may be considered. uterus, and the left tube is abnormal and enlarged. possible; for example, large ﬁbroids may be removed.

OVULATION PROBLEMS CERVICAL PROBLEMS panel, below), mucus can become hostile to normal sperm, or the amount produced or its consistency may FAILURE OF THE OVARIES TO RELEASE A MATURE EGG EVERY VARIOUS FACTORS CAN AFFECT CERVICAL-MUCUS change. If cervical mucus antibodies are the suspected MONTH IS A COMMON CAUSE OF INFERTILITY. IT HAS PRODUCTION AND PREVENT A SPERM’S NORMAL VARIOUS POSSIBLE CAUSES. PASSAGE INTO THE UTERUS VIA THE CERVIX. cause, a sample of mucus is analyzed shortly after intercourse. If antibodies are present, corticosteroid The release of eggs from the ovaries is controlled by a To meet a mature egg, a sperm must ﬁrst pass drugs may be given to suppress their production or complex system of hormones from the hypothalamus, through the cervix. The mucus produced by the intrauterine insemination may be used to introduce the pituitary gland, and ovaries, which work in harmony cervix acts as a temporary repository and transport sperm directly into the uterus. Other underlying causes, to maintain the system. Problems can arise if the system medium for the sperm. For a variety of reasons (see such as medications, may be dealt with as appropriate. is interrupted. Polycystic ovarian syndrome (see p.219) is a common cause. Others include noncancerous pituitary FACTORS THAT AFFECT CERVICAL gland tumors and thyroid problems (thyroid hormones ANTIBODIES TO SPERM MUCUS are also important for fertility). Excessive exercise, obesity, Sometimes cervical mucus being extremely underweight, and stress may result in “reacts” to sperm by There are various conditions that can affect producing antibodies that a hormone imbalance. Early menopause may also cause cervical mucus, making it hostile toward sperm destroy them before they in some way, reducing the amount produced, or a failure to ovulate. Blood have an opportunity to tests can check hormone fertilize an egg. having a damaging effect on its quality (see p.41). levels, and an ultrasound DRUGS THAT AFFECT HEALTH CONDITIONS scan can check the ovaries. Antibody MUCUS THAT AFFECT MUCUS Causes are treated when Clomifene citrate, used in Polycystic ovarian syndrome possible, but sometimes Cervix no cause is found. Drugs the treatment of infertility, (see p.219) can be associated is a common cause of with poor cervical-mucus may be given to stimulate hostile mucus. production. ovulation or, in some cases, assisted conception Antihistamines reduce the Infections, such as yeast or is considered. production of mucus (the vaginosis (see p.220), can sperm’s transport medium affect mucus production EXCESSIVE EXERCISE through the cervix). by the cervix. The delicate balance of hormones that leads to the Cervical Dicyclomine, used to treat Damage to the cervix, monthly release of a mature mucus irritable bowel syndrome, perhaps as a result of a egg from the ovaries can be can also reduce cervical- biopsy, can affect its ability disrupted by frequent mucus production. to produce mucus. strenuous exercise. Sperm

216 FERTILITY DISORDERS MALE FERTILITY DISORDERS In about one-third of couples with infertility, the problem lies with sperm delivery is a problem. Difﬁculties delivering sperm can occur the man. Male fertility problems can be divided into two main at any point within the complex system of tubes that carry sperm groups—those that affect sperm production and those in which from the testes to the penis or may relate to ejaculation itself.

PROBLEMS WITH DIFFICULT PASSAGE EJACULATION I DISORDERS SPERM PRODUCTION OF SPERM PROBLEMS A SPERM COUNT MAY BE LOW, OR THE SPERM PRODUCED THE PASSAGE OF SPERM THROUGH THE COMPLEX SYSTEM SOMETIMES, HEALTHY SPERM CANNOT BE ARE ABNORMAL AND UNABLE TO FERTILIZE AN EGG. VARIOUS OF TUBES WITHIN THE MALE REPRODUCTIVE SYSTEM MAY DELIVERED TO THE TOP OF THE VAGINA, CAUSES ARE POSSIBLE BUT, OFTEN, NO CAUSE IS FOUND. BE COMPROMISED FOR SEVERAL REASONS. COMMONLY DUE TO ERECTILE DYSFUNCTION. Factors that elevate the temperature within the scrotum, Damage to the sperm-transporting tubes (vasa deferentia Erectile dysfunction (ED), or the such as a varicocele (see p.222), can affect sperm production, and epididymides), perhaps due to a sexually transmitted inability to achieve or maintain an as can long-term illnesses, damage to the testes, smoking, infection, may affect the passage of sperm. It may be possible erection, is a common cause of male alcohol, and certain drugs. Testosterone-related problems to treat the damage with microsurgery. Sometimes, following infertility; it may reflect emotional may be the cause, for which, rarely, there is an underlying prostate surgery, the valves that prevent backflow of semen problems, such as anxiety or depression chromosomal abnormality. Such causes are considered into the bladder at ejaculation (retrograde ejaculation) do not or, less commonly, medical conditions, during an examination and investigated with blood tests. close properly. In this case, artificial insemination may be such as a long-standing vascular Underlying causes are treated where possible; otherwise, used to try to achieve conception. disease that affects the blood supply to assisted conception may be considered (see panel below). the penis or diabetes mellitus, if the INFLAMED VAS DEFERENS The vasa deferentia may be nerve supply to the penis is impaired. inflamed due to a sexually Prescribed drugs, including some of transmitted infection, such those for treating high blood pressure, as gonorrhea. may also be involved in causing ED. In THERMOGRAM addition, heavy drinking of alcohol and OF VARICOCELE This thermogram smoking can be associated with it. shows the elevated Treatment aims to identify and resolve temperature (red the underlying cause of the problem area) within a through psychological or medical varicocele (enlarged treatments as appropriate, but if this vein in the testis) Sperm-making is not possible, artificial insemination compared with the LOCATION OF THE seminiferous Narrowed rest of the testes. VAS DEFERENS tubules vas deferens may provide the solution.

ASSISTING CONCEPTION

Since the birth of the ﬁrst IVF baby in 1978, major advances have been made. Simple forms of treatment involve the use of fertility drugs, while more complex techniques can introduce sperm directly into the uterus at the time of ovulation (intrauterine insemination) or inject a single sperm into an egg. The use of donor eggs and sperm is now common, and surrogacy is also considered as an available option.

IVF of an IVF program. Only one sperm is In vitro fertilization (IVF) can be used in needed, which is injected straight into many situations, including when fallopian an egg taken from the ovary of the tubes are damaged or no cause has been woman. Sperm can be taken either from found for fertility problems. Fertility drugs a semen sample or directly from the are usually given to stimulate egg epididymis or testes. As with IVF, fertility production before the procedure takes drugs can be given ﬁrst and the best INTRACYTOPLASMIC SPERM INJECTION place. The eggs that are produced are embryos are transplanted directly into In this microscopic technique, an egg is fertilized removed from the ovaries using a needle the uterus via the cervix. by using a needle (seen to the right in this image) passed through the vaginal wall and are to inject a single sperm cell directly into the egg. combined with the sperm in a laboratory. GIFT 40 One or two fertilized eggs are introduced Gamete intrafallopian transfer (GIFT) is into the uterus using a catheter (a thin similar to IVF except that eggs and sperm 30 tube) inserted through the cervix. If the are transferred directly to the fallopian IVF SUCCESS RATES The success rates of cycle is successful, one or both embryos tubes, where fertilization takes place. Less 20 will implant in the wall of the uterus. commonly used, zygote intrafallopian IVF are related to a transfer (ZIFT) involves the transfer of a woman’s age; these

are greatest in (%) RATE SUCCESS 10 ICSI zygote (newly fertilized egg) into the women under the Intracytoplasmic sperm injection (ICSI) is tubes. These methods are used when the age of 35, then 0 used to help couples when the problem sperm count is low, sperm motility is poor, decrease gradually UNDER 35–37 38–39 40–42 43–44 OVER 35 44 lies with the man and can be used as part or infertility is unexplained. with increasing age. AGE OF WOMEN (YEARS)

217 FEMALE REPRODUCTIVE DISORDERS

MANY CONDITIONS CAN IMPACT UPON THE COMPLEX SYSTEM OF FEMALE BLOCKED, OR A CONDITION AFFECTING THE UTERUS MAY PREVENT THE REPRODUCTIVE ORGANS, AFFECTING THE REPRODUCTIVE PROCESS AT ONE NORMAL IMPLANTATION OF A FERTILIZED EGG. MANY OF THESE CONDITIONS OF ITS DIFFERENT STAGES. FOR EXAMPLE, THE PRODUCTION OF EGGS MAY BE CAN BE TREATED, OR THE PROBLEM MAY BE BYPASSED BY ONE OF SEVERAL IMPAIRED, THE PASSAGE OF THE EGG ALONG THE FALLOPIAN TUBE MAY BE METHODS OF FERTILITY TREATMENTS NOW AVAILABLE.

ENDOMETRIOSIS during menstruation. This condition may reduce fertility INSIDE THE ABDOMEN in several ways; one is thought to be blockage of the This laparoscopic IN THIS COMMON DISORDER, PIECES OF TISSUE THAT view shows a dark fallopian tubes by scar tissue. Symptoms, if present, USUALLY LINE THE UTERUS ARE FOUND ELSEWHERE IN THE endometrial lesion PELVIS AND ABDOMEN, WHICH CAN CAUSE INFERTILITY. may include pain, heavy or irregular periods, pain on on an ovary. urinating, and painful intercourse. Endometriosis may The lining of the uterus (endometrium) thickens every be diagnosed by laparoscopy, in which the internal month in preparation for pregnancy, then is shed if organs are examined using a viewing instrument passed Probe fertilization does not occur. Fragments of endometrium through the abdominal wall. Treatment options include may become attached to other tissues and organs in the drugs, such as the combined oral contraceptive pill or Endometrial lesion abdomen and pelvis, where they continue to respond other hormones that temporarily stop menstruation, or to the hormonal changes of the menstrual cycle, laser treatment of the lesions. bleeding and causing pain when menstruation occurs. Hysterectomy and removal of Uterus

FEMALE REPRODUCTIVE DISORDERS I FEMALE REPRODUCTIVE DISORDERS Scar tissue eventually forms at these bleeding sites, and the ovaries and other affected ovarian cysts may develop. The cause of endometriosis tissue may be recommended is not fully understood, but endometrial fragments may for women who no longer pass along the fallopian tubes and into the abdomen wish to have children. Ovary

Around the fallopian tubes

In the uterine Around the muscle layer ovaries (myometrium)

In the rectum On the exterior of the uterus

On the bladder In the area between the WHERE ENDOMETRIAL rectum and TISSUE CAN BE FOUND the uterus Misplaced endometrium can be found anywhere in ENDOMETRIAL TISSUE IN THE VAGINA the abdomen and pelvis, This microscopic view shows the multiple “chocolate” cysts including in the bowel and (named because of the color) of abnormal tissue typical of around the bladder. The endometriosis. These cysts bleed during menstruation. In the vagina ovaries are common sites.

PELVIC INFLAMMATORY DISEASE INFLAMMATION OF PELVIC ORGANS, IN PARTICULAR THE FALLOPIAN TUBES, CAN BLOCK THE PASSAGE OF EGGS AND SPERM. SEXUALLY TRANSMITTED DISEASES, SUCH AS CHLAMYDIA, ARE COMMON CAUSES.

Pelvic inflammatory disease (PID) may addition to increasing the risk of infertility, be symptomless, discovered only when PID may make an ectopic pregnancy a woman is investigated for fertility more likely. Investigations may include problems. The infection starts in the taking swabs from the cervix to look for vagina, and passes up into the uterus, infections, an ultrasound scan to check fallopian tubes, and, sometimes, the for swelling in the fallopian tubes, and ovaries. Having a coil (intrauterine device) a laparoscopy to look for inflammation. may increase the risk of PID. Women PID is treated with antibiotics. with PID may have abnormal vaginal discharge, fever, pain during intercourse, and heavy or prolonged periods. Urgent X-RAY VIEW OF A PELVIS A fallopian tube may become filled with pus in treatment may be required if the condition PID, making it swell up, as seen in this contrast comes on suddenly and is associated with X-ray taken following the introduction into Infected, pus-filled severe pain and a high temperature. In the vagina of special dye via a catheter. Healthy fallopian tube Uterus Probefallopian tube Pelvis

218 FEMALE REPRODUCTIVE DISORDERS

Fallopian tube Subserous ﬁbroid UTERINE FIBROIDS AND POLYPS Grows under the outer THESE ARE NONCANCEROUS GROWTHS WITHIN THE UTERUS AND CERVIX. surface of the uterus FIBROIDS DEVELOP WITHIN THE MUSCULAR WALL, WHILE POLYPS PROTRUDE FROM THE INNER LINING. LARGE FIBROIDS CAN CAUSE FERTILITY PROBLEMS.

Fibroids are common and consist of instrument is passed up the vagina and muscle and fibrous tissue. The cause through the cervix to look inside the of their development is unknown, but uterus). Small fibroids and uterine polyps may relate to the female sex hormone may be removed during hysteroscopy; estrogen. As fibroids enlarge, they may larger fibroids can be removed through begin to produce symptoms, such as an abdominal incision. Hysterectomy Uterine polyp Ovary painful, prolonged, and heavy periods. may be considered for women who Grows into the uterine cavity If large, they can distort the cavity within no longer wish to become pregnant. Submucosal fibroid the uterus, causing recurrent miscarriages Intramural fibroid Grows under the lining and affecting fertility if implantation Grows within the becomes a problem. Fibroids can also wall of the uterus I DISORDERS cause a fetus to lie in an abnormal Cervical fibroid position. Polyps can cause bloodstained Grows within the cervix discharge, as well as bleeding after LARGE FIBROIDS intercourse and between periods. They Fibroids can be singular may be seen when looking at the cervix or there may be several SITES OF UTERINE through a speculum (the instrument used present. These muscular GROWTHS growths can reach the to hold the vaginal walls apart) and may Fibroids can grow in the size of a grapefruit. outer, middle, or inner be removed at this time. Both polyps and They can be seen on layers of the uterus. Polyps fibroids may be diagnosed by ultrasound ultrasound scans and can appear on the uterine or hysteroscopy (in which a viewing sometimes on X-rays. or cervical lining.

OVARIAN CYSTS POLYCYSTIC OVARIAN SYNDROME THESE FLUID-FILLED GROWTHS CAN OCCUR SINGLY OR THERE MAY THIS COMMON CONDITION, WHICH IS OFTEN ASSOCIATED WITH FERTILITY PROBLEMS BE MANY. CYSTS DO NOT AFFECT FERTILITY, UNLESS THEY OCCUR RELATED TO AN IMBALANCE IN THE LEVELS OF THE SEX HORMONES, IS CHARACTERIZED AS A RESULT OF POLYCYSTIC OVARIAN SYNDROME. BY MULTIPLE SMALL, FLUID-FILLED CYSTS PRESENT ON THE OVARIES. Cysts on There are many types of ovarian cyst. discomfort, and painful intercourse. In polycystic ovarian syndrome Fallopian tube Uterus ovary Some develop from the follicles in which Occasionally, cysts may cause an (PCOS), hormone levels are disrupted; eggs mature in the ovaries. Others form emergency situation if they burst often, the levels of testosterone and LH from the corpus luteum, which develops or become twisted. Some types may (luteinizing hormone), produced by from the follicle after ovulation. Dermoid become huge and ﬁll most of the the pituitary gland, are higher than cysts contain tissues found in other abdomen. Cysts may be diagnosed by normal, resulting, in some cases, in parts of the body, such as skin. Ovarian ultrasound scan or by laparoscopy. a failure to ovulate, associated with cysts may occur singly or in multiples, They may resolve without treatment absent or irregular periods. Other as in polycystic ovarian syndrome (see or may be removed surgically. Those features of PCOS include obesity, acne, right). They tend to be symptomless, that are removed are checked for and hirsutism. Affected women are but if symptoms do develop, they may cancerous cells because cysts are very more likely to develop resistance to include irregular periods, abdominal occasionally malignant. the sugar-regulating hormone insulin and may develop diabetes mellitus. Uterus Cyst in ovary Diagnosis involves blood tests to check hormone levels and ultrasound scans to look for ovarian cysts. Drugs, in particular clomifene, may help restore fertility, and the combined oral contraceptive pill can be used if the aim is to restore regular periods. OVARIES WITH MULTIPLE CYSTS This MRI scan of a uterus, fallopian tubes, and ovaries clearly shows multiple cysts Fluid-ﬁlled cyst on (seen in white) on both outer wall of ovary ovaries, particularly the left.

CYST LOCATION CLINICAL FEATURES Cysts can develop on the CLOSE-UP VIEW OF AN OVARIAN CYST The hormonal imbalance of surface of an ovary or within Ovarian cysts can become very large, even PCOS has some unwanted it. They can be present on larger than the one shown here. The outer effects, including excessive one or both ovaries, either surface of a cyst can be stretched by the body and facial hair. Acne singly or as multiples. large amount of ﬂuid inside. may also be a problem.

219 TRICHOMONAS VULVOVAGINITIS VAGINALIS MENSTRUAL PROBLEMS THIS CONDITION IS AN INFLAMMATION OF THE VULVA This highly magnified The menstrual cycle and bleeding may be AND VAGINA, WHICH MAY CAUSE DISCOMFORT, ITCHING, image shows a parasitic AND DISCHARGE. THE CAUSE IS USUALLY AN INFECTION. microorganism that can disrupted in a number of ways, some of cause vulvovaginitis. which may cause problems when trying to Likely infective causes include Candida albicans (yeast), Trichomonas vaginalis, or an excessive quantity of the conceive. Periods may be heavy, irregular, bacteria that normally inhabit the vagina (see bacterial absent, or painful. Treatments will be vaginosis, below). Another cause may be irritants, such available in many cases, either to relieve as substances found in laundry detergents. Swabs are Inflamed labia the symptoms or to treat the underlying taken and, if a bacterial cause is found, antibiotics cause. When conception is a problem, are prescribed. Very rarely, cancerous cells are present, AFFECTED GENITALIA fertility treatments may be considered. so in some cases, a tissue sample is taken to exclude The inner surfaces of the labia, cancer. Any possible irritants should be avoided. The as well as the vaginal wall, condition usually clears with treatment, but may recur. become red and inflamed. MENORRHAGIA THIS TERM DESCRIBES HEAVY PERIODS THAT CANNOT BE CONTROLLED EFFECTIVELY BY SANITARY NAPKINS OR BACTERIAL VAGINOSIS There is a delicate balance of bacteria in the healthy TAMPONS OR INVOLVE PASSING LARGE BLOOD CLOTS. THIS CONDITION RESULTS FROM AN OVERGROWTH OF vagina, the main ones being Gardnerella vaginalis and BACTERIA THAT ARE NORMALLY PRESENT IN THE VAGINA. Mycoplasma hominis. If the balance is disrupted, Excessively heavy periods can be prolonged and

FEMALE REPRODUCTIVE DISORDERS I FEMALE REPRODUCTIVE DISORDERS ANTIBIOTICS MAY BE NEEDED TO TREAT THE CAUSE. symptoms such as discharge and itching around the painful, and anemia may become a problem. Possible vulva or vagina may develop, but bacterial vaginosis causes include fibroids, a uterine polyp (see p.219), can be symptomless. The cause is unknown, but the and using a coil, although often no cause is found. presence of a sexually transmitted disease (STD) may Rarely, cancer is the cause. Blood will be tested for disrupt the balance. Bacterial vaginosis may affect anemia. Other tests include ultrasound scanning fertility by causing pelvic of the uterus and hysteroscopy, in which a viewing GARDNERELLA inflammatory disease (see p.218). instrument is passed into the uterus via the cervix. A VAGINALIS Swabs are taken to look for an sample of the lining may also be taken. Underlying The bacterium seen infection that might cause the causes are treated and, in this electron condition and antibiotics are otherwise, drugs may be micrograph can cause a watery prescribed as appropriate. The given to reduce bleeding. vaginal discharge woman’s partner should be tested with a fishy odor. and treated if an STD is found. THE ROLE OF PROGESTERONE This highly magnified image shows crystals of progesterone. A drop in BARTHOLINITIS the levels of circulating INFLAMMATION OF ONE OR BOTH OF THE SMALL GLANDS progesterone is the trigger for menstrual bleeding. THAT OPEN INTO THE VULVA TO RELEASE A LUBRICANT Vaginal entrance DURING INTERCOURSE IS KNOWN AS BARTHOLINITIS. 150 The pea-sized Bartholin’s glands open into either side of the vulval area, each via a tiny duct. These glands may become inflamed due to a bacterial infection. Poor 125 hygiene or a sexually transmitted disease, such as gonorrhea, may be potential causes. The duct leading from a gland to the vulva may become blocked, 100 causing a fluid-filled cyst (known as a Bartholin’s cyst), or an abscess (a pus-filled swelling) may develop. Abscesses are caused by 75 infection, most commonly due to the Labia majora bacteria Staphylococcus or E. coli, and are very painful and require prompt (ml) LOSS BLOOD treatment. Antibiotics are prescribed Vaginal entrance 50 for bartholinitis, which should clear the condition. In the meantime, analgesics Cyst within may be needed to relieve discomfort. Bartholin’s gland 25 Cysts are usually left alone, unless they become very large and cause problems. ENLARGEMENT OF A The pus may be drained from an abscess BARTHOLIN’S GLAND 0 through a small cut made in its wall. Here, a fluid-filled NORMAL MODERATELY EXCESSIVELY HEAVY HEAVY The incision may be sutured open swelling has developed in the right Bartholin’s BLOOD LOSS DURING MENSTRUATION so that it heals in this position, gland as a result of This chart represents blood loss during one menstrual preventing further abscesses from blockage of the duct period. Normal blood loss is up to 60 ml; moderately forming. Bartholinitis may recur. that drains the gland. heavy is 60–100 ml; and excessive loss is more than 100 ml.

220 FEMALE REPRODUCTIVE DISORDERS METRORRHAGIA AMENORRHEA IRREGULAR PERIODS, WITH THE TIME WHEN THERE IS NO MENSTRUATION BETWEEN EACH PERIOD VARYING, IS WHATSOEVER, THE CONDITION IS KNOWN AS METRORRHAGIA. KNOWN AS AMENORRHEA.

The most common cause of irregular Primary amenorrhea is the failure to periods is a disruption in the normal start menstruation by the age of 16. It balance of the hormones that control may be part of delayed puberty, and the menstrual cycle. Such a disruption specialized investigations will look for a occurs quite naturally following cause. Secondary amenorrhea is when pregnancy and childbirth. But hormonal periods stop for three months or more imbalance may also occur during a in a woman who has previously been long-term illness, and in times of stress menstruating and the cessation cannot and anxiety. Excessive exercise or be explained by the usual causes (for dramatic weight loss may also affect example, she is not breastfeeding, has not hormonal balance. Irregular periods just had a baby, has not just stopped I DISORDERS may be a feature of polycystic ovarian taking the combined oral contraceptive syndrome (see p.219). The onset of pill, or has not reached menopause). menopause is often signalled by Disruption of the normal balance of the 15 RIGOROUS ROUTINES irregular periods. However, for many female sex hormones is usually the cause, Frequent strenuous exercise can disrupt hormones, resulting in absent periods—a affected women, there is no obvious often due to stress, excessive exercise, or 14 condition that notoriously affects ballerinas. cause. Often, irregular periods will settle weight loss; as part of polycystic ovarian back into a proper rhythm, but tests syndrome (see p.219); or occasionally, 13 START OF PERIODS LINKED TO WEIGHT may be arranged to look for a cause, due to a pituitary disorder, such as a Girls of normal weight tend to get their ﬁrst including blood tests to check hormone tumor. Tests include blood tests to check 12 period (menarche) around the age of 13 years. This age may vary for girls who are obese or levels and an ultrasound scan of the hormone levels, an ultrasound scan of overweight, and those who are underweight. uterus and ovaries. Underlying causes the uterus and ovaries, and a CT scan 11 are treated as appropriate and, of the pituitary gland. Underlying causes (YEARS) OF MENARCHE AGE KEY otherwise, drugs may be given to will be treated and, if this is not 10 AVERAGE AGE OF MENARCHE AGE OF MENARCHE FOR 50 regulate periods, such as the combined possible, hormone treatments may be 9 OBESE/ NORMAL UNDER- PERCENT OF GIRLS oral contraceptive pill. prescribed to trigger menstruation. OVERWEIGHT WEIGHT WEIGHT FULL AGE RANGE FOR MENARCHE

DYSMENORRHEA ABNORMALITIES OF THE UTERUS PAIN IN THE LOWER ABDOMEN JUST BEFORE AND DURING MENSTRUATION IS A COMMON PROBLEM THAT AFFLICTS An abnormally shaped uterus is present at birth, UP TO 75 PERCENT OF WOMEN AT SOME TIME. because it has not developed properly, but is often Dysmenorrhea can be either primary (no identified picked up only when a woman becomes pregnant or Fundus of uterus if she undergoes investigations for fertility problems. cause) or secondary (due to a problem in the pelvic The shape can be abnormal in a number of ways (see organs). The former tends to be present in the teens “Triangular” and resolves with time. The latter is characterized by diagrams, below). The abnormality can be identified uterine cavity by an ultrasound scan, which may show that there is Neck of severe pain in women who have had little pain before, a partial uterus or that the cavity is divided into two uterus for which pelvic inflammatory disease (see p.218) and NORMAL UTERUS (cervix) sections. Recurrent miscarriages or preterm labor The uterus usually has endometriosis (see p.218) are possible causes. Swabs may occur as a result of an abnormally shaped uterus. one cavity and is of a to detect infection and pelvic ultrasound scanning are symmetrical shape. used in the diagnosis. Primary dysmenorrhea may be improved by nonsteroidal anti-inflammatory drugs Single or the combined oral contraceptive pill. In secondary “horn” of uterus dysmenorrhea, the underlying cause is treated.

Two “horns” of uterus Abnormal Septum Small uterine uterine cavity divides cavity the cavity

UNICORNUATE UTERUS BICORNUATE UTERUS SEPTATE UTERUS In this abnormality, only one side Here, the uterus has two horns, The septate uterus has a long central of the uterus is present, so that so that both sides of the uterus division that almost divides the cavity PROSTAGLANDINS—MEDIATORS OF PAIN the uterine cavity is small and are narrow, with a deep division into two halves, thereby limiting the Levels of prostaglandins rise shortly after ovulation, triggering very narrow. down the center. space for growth of a fetus. contractions in the uterine muscles that affect the blood supply to the uterus, causing the pain of primary dysmenorrhea.

221 MALE REPRODUCTIVE DISORDERS

THE ORGANS OF THE MALE REPRODUCTIVE SYSTEM MAY BE AFFECTED BY A SUCH AS INFLAMMATION OF THE TESTIS AND THE EPIDIDYMIS DUE TO MUMPS, VARIETY OF DISORDERS, INCLUDING PROBLEMS CAUSED BY INFECTIONS AND MAY IMPACT ON A MAN’S FERTILITY. DISORDERS OF THE MALE REPRODUCTIVE THOSE RELATED TO ABNORMAL GROWTHS. SOME OF THE CONDITIONS MAY SYSTEM THAT IMPAIR THE ABILITY TO PRODUCE HEALTHY SPERM OR TO AFFECT NORMAL FUNCTION DURING SEXUAL INTERCOURSE WHILE OTHERS, DELIVER SPERM TO MEET AN EGG WILL OBVIOUSLY AFFECT FERTILITY.

EPIDIDYMAL CYSTS EPIDIDYMO-ORCHITIS THESE PAINLESS SWELLINGS CONTAINING CLEAR FLUID (ALSO KNOWN WHEN ONE OF THE TESTES AND ITS ADJACENT AS SPERMATOCELES) OFTEN DEVELOP IN THE EPIDIDYMIS, THE COILED TUBE EPIDIDYMIS BECOME INFLAMED, IT OFTEN CAUSES THAT STORES SPERM AND TRANSPORTS THEM AWAY FROM THE TESTES. SEVERE PAIN AND SWELLING ON THE AFFECTED SIDE.

Why these cysts develop is unknown. up (transillumination); an ultrasound The inflammation is usually caused by a bacterial They tend to grow slowly, are usually scan can confirm the diagnosis. infection, either from the prostate gland (see prostatitis, symptomless, and do not become Treatment is seldom needed because opposite) or the urinary tract or, in younger men, a cancerous. In many cases, there are the cysts tend to be small. Occasionally, sexually transmitted disease (see pp.224–25). Before many cysts, often on both sides; but a large one may compress surrounding mumps vaccinations were included in the routine CAUSATIVE ORGANISM Chlamydia bacteria, shown in it is possible to have just one cyst on tissues, causing discomfort, so that childhood immunizations, mumps was a common pink on this color-enhanced MALE REPRODUCTIVE DISORDERS I MALE REPRODUCTIVE DISORDERS one side. It is very important to have a removal is recommended. Surgical cause of epididymo-orchitis in boys and young men. electron micrograph, can medical check if a swelling is discovered treatment does not affect fertility. In some cases, it may affect fertility. The symptoms cause epididymo-orchitis. in the scrotum to rule out testicular include pain, redness, and swelling on the affected cancer. Cysts can be diagnosed during side, often with a high temperature. Swabs may a clinical examination by shining a light be taken from the urethra and samples of underneath so that the swelling lights urine collected to discover the cause of the inflammation. Sometimes, an ultrasound scan is arranged to rule out testicular torsion MULTIPLE CYSTS Vas deferens (see opposite). Antibiotics are prescribed Epididymal cysts are for a bacterial infection smooth and spherical Epididymis INFLAMED AREA in shape. They may as well as analgesics. Ice Both the testis and occur alone, but Penis packs can help relieve the epididymis are often there are many the discomfort too. The inflamed, causing cysts on both sides. Testis pain should subside tenderness, swelling, Occasionally, they and redness. In Epididymal cyst within 48 hours, but the severe cases there become infected, in Epididymis which case they may swelling may persist for may be extreme be painful. Scrotum a few weeks. pain and fever. Testis

VARICOCELE Testicular vein Testicular artery THIS KNOT OF DISTENDED VEINS IN THE SCROTUM MAY CAUSE DISCOMFORT Testicular artery Bulging FOR SOME MEN AND CAN RESULT IN A REDUCED SPERM COUNT. FOR SOME varicose Cremasteric UNKNOWN REASON, THE LEFT-HAND SIDE IS MOST COMMONLY AFFECTED. veins artery Varicoceles are varicose veins in the scrotum, which result from leaky Pampiniform plexus valves within veins that take blood away from the testes; there is a backflow of blood into the scrotum and a buildup of blood, distending the veins Artery to and causing them to look like a bag of worms. Symptoms may include ductus discomfort, a dragging sensation, and scrotal swelling. It is usually possible deferens to confirm the diagnosis on clinical examination. In the majority of cases, varicoceles are small and do not require any treatment—they either cause VARICOCELE VEINS no problems or resolve. Close- Affected veins are fitting underwear that provides bulging and irregular due to the backflow support can help relieve the of blood from the discomfort and the aching, veins that drain dragging sensation. If the pain the testes. is problematic or fertility is affected, treatment may be recommended, which involves tying off the distended veins. NORMAL TESTICULAR VEINS CONTRAST X-RAY OF A VARICOCELE These veins drain blood A varicocele is highlighted by a special from the testes. Backflow dye that has been injected into the is prevented by a system bloodstream before X-rays are taken. of valves.

222 MALE REPRODUCTIVE DISORDERS HYDROCELE BALANITIS THIS SWELLING RESULTS FROM AN ABNORMAL ACCUMULATION OF FLUID INFLAMMATION AT THE END OF THE PENIS, OR BETWEEN LAYERS OF THE SCROTAL SAC THAT SURROUND EACH TESTIS. BALANITIS, CAN BE SORE AND UNCOMFORTABLE. HYDROCELES ARE RARELY PAINFUL BUT CAN BE UNCOMFORTABLE IF LARGE. FORTUNATELY, MOST CAUSES ARE EASILY TREATED.

When a hydrocele is present, there is an abnormally large volume of fluid In this condition, the end of the penis (the glans) present within layers of the scrotal sac (see p.29). Infections and testicular and the foreskin become inflamed, making them sore, injuries are possible causes. Hydroceles tend to occur in young boys and itchy, and reddened. In addition, there may be some elderly men. Diagnosis is made by a clinical examination—the swelling discharge from the urethra. Possible causes include will light up when a flashlight is held against it—and by ultrasound bacterial infections, yeast (Candida albicans), and scanning. If the symptoms of a hydrocele become troublesome, sexually transmitted diseases (see pp.224–25). In some treatment options include drainage cases, a tight foreskin may make it difficult to clean of the fluid with a needle or a the end of the penis properly. After a physical small operation. Any infections examination of the penis, swabs may be taken from Testis are treated with a course of the end of the urethra and tested for possible I DISORDERS antibiotics. Scrotum Clear fluid infectious organisms, which are treated accordingly. A circumcision (removal of the foreskin) may be TESTICULAR SWELLING SWELLING WITHIN THE SCROTUM recommended in cases of a tight foreskin. Some cases A hydrocele is characterized by painless A hydrocele is one possible cause of swelling on one side of the scrotum only; testicular swelling; fluid accumulates of balanitis are due to an allergic reaction. If possible, in this image the man’s right testis is around a testis and, if large enough, the irritant is identified and then avoided. The end swollen, but the left looks normal. can distort the shape of the scrotum. of the penis should be kept clean and dry.

TESTICULAR TORSION PROSTATITIS THIS PAINFUL CONDITION NEEDS URGENT TREATMENT THIS COMMON CONDITION MAY OCCUR IN TWO FORMS: A PAINFUL, ACUTE FORM BECAUSE THE TESTIS MAY BE IRREPARABLY DAMAGED IF AND AN OFTEN SYMPTOMLESS CHRONIC ONE. BOTH REQUIRE TREATMENT OF THE SURGERY IS NOT PERFORMED WITHIN ABOUT 24 HOURS. UNDERLYING CAUSE IF ONE CAN BE IDENTIFIED. THE PROBLEM MAY RECUR.

For reasons that remain unclear, the spermatic cord, This condition particularly affects during a rectal examination. Samples which contains the vas deferens and the blood sexually active men. Often a cause of urine, prostatic secretions, and swabs vessels to the testis, becomes twisted, compromising cannot be found, but prostatitis may be taken from the end of the urethra are the blood supply to the testis, which can cause due to a sexually transmitted disease tested for infections. Ultrasound or permanent damage if not reversed quickly. The onset (see pp.224–25) or a bacterial infection CT scanning may be used to look for of symptoms is rapid, including pain in the scrotum, of the urinary tract. Acute prostatitis an abscess in the prostate, a possible lower abdomen, and groin, as well as redness on one produces severe and rapidly developing complication. The underlying cause, side of the scrotum. The condition is diagnosed by symptoms including a high temperature, such as infection, is treated, but it may ultrasound scanning. After diagnosis, surgery to pain in the root of the penis, and pain take months for the disorder to subside. untwist the cord and then ﬁx both testes in place in the lower back. Chronic prostatitis is usually undertaken quickly. If the testis cannot may be symptomless or produce only be saved in time, it is removed—an implant may be mild symptoms, which may include put in its place for cosmetic reasons. If one testis is pain in the root of the penis, in the ENTEROCOCCUS FAECALIS damaged during a torsion event, the unaffected testis testes, and in the lower back, pain when BACTERIA can usually make enough sperm so that fertility is ejaculating, and blood in the semen. In This electron micrograph shows bacteria that are not signiﬁcantly affected. both types, there may be frequent and normally present in the gut, sometimes painful urination. A Twisted but may cause prostatitis and spermatic cord physician assesses the prostate gland urinary-tract infections.

Bladder Rectum Vas deferens

Blood vessels Vas deferens Inflamed prostate gland Prostate gland Urethra becomes Testis twisted Urethra narrowed around Scrotum NORMAL PROSTATE GLAND ENLARGED PROSTATE GLAND TORSION OF THE TESTIS Usually the prostate gland (the size of a walnut) sits just In prostatitis, the gland is inflamed and can swell. The In addition to the twisting of the spermatic cord, the below the neck of the bladder and surrounds the urethra. swollen prostate can compress the urethra so that urine testis lies in a different position in the scrotum. The Urine from the bladder flows freely into the urethra, which cannot pass freely from the bladder as it should. This usual shape of the scrotum may be distorted. carries it out through the penis during urination. means that urine is passed frequently and in small amounts.

223 SEXUALLY TRANSMITTED DISEASES

MOST TYPES OF SEXUALLY TRANSMITTED DISEASES (STD) ARE PASSED FROM PERSON TO PERSON DURING SEXUAL INTERCOURSE. SOME, SUCH AS HIV AND SYPHILIS, CAN ALSO CROSS THE PLACENTA AND AFFECT THE FETUS, WHILE OTHERS, SUCH AS GONORRHEA AND CHLAMYDIA, CAN AFFECT FERTILITY. SOME CAN ALSO BE TRANSFERRED FROM MOTHER TO CHILD DURING DELIVERY AS THE BABY EMERGES THROUGH THE BIRTH CANAL.

HIV/AIDS can cope for some time, but eventually the CD4 white cell count falls below a critical level. Most people who become infected with HIV have no symptoms initially. Some INFECTION WITH THE HUMAN IMMUNODEFICIENCY VIRUS (HIV), IF LEFT UNTREATED, LEADS TO ACQUIRED IMMUNODEFICIENCY SYNDROME (AIDS) AND SEVERELY IMPAIRED have the general symptoms typical of a viral illness, including fever, aching muscles IMMUNITY. HIV CAN BE PASSED TO A FETUS IN UTERO AND TO A BABY VIA BREAST MILK. and joints, swollen glands, and a sore throat. There usually follows a symptom-free interval, which may last for many years. Some people, however, may have further HIV can be transferred by vaginal, anal, and oral intercourse, contaminated blood relatively mild symptoms, including thrush in the mouth, gum disease, and weight and blood products, and contaminated needles. It can also be passed to a fetus loss. Eventually, when the CD4 count falls below a certain level or certain conditions during pregnancy (HIV particles can cross the placenta), during childbirth, or after develop, such as particular infective illnesses and certain cancers, the person is said delivery in breast milk. The virus infects a type of white blood cell that has the CD4 to have AIDS. Treatment of HIV and AIDS involves combinations of antiretroviral receptor on its surface and replicates rapidly, killing the cells in the process. The body drugs and antibiotics. Condoms reduce the risk of HIV transmission.

HIV particles infect WEAKENING THE BODY’S HIV particle white blood cells IMMUNE SYSTEM W & C EUROPE, NORTH SEXUALLY TRANSMITTED DISEASES I SEXUALLY DISORDERS AMERICA, AUSTRALIA, and multiply inside HIV particles target and AND NEW ZEALAND infect white blood cells and turn them into viral factories. EASTERN EUROPE AND CENTRAL ASIA The cells rupture and release HIV particles into the bloodstream. Antiretroviral LATIN AMERICA drugs interfere with HIV replication at one stage PREVENTING HIV of its reproductive cycle. CARIBBEAN TRANSMISSION Antiretroviral drugs are SUB-SAHARAN AFRICA given in pregnancy. The proportion of infected women being treated is ASIA highest in developed countries and lowest in NORTH AFRICA AND developing countries. It is Once released THE MIDDLE EAST crucial to treat pregnant from cell, HIV women to improve their particle repeats 0 20 40 60 80 100 outlook and reduce the cycle of infection INFECTED PREGNANT WOMEN RECEIVING likelihood of transfer of ANTIRETROVIRAL THERAPY (%) infection to the baby.

SYPHILIS Primary syphilis GENITAL HERPES THIS BACTERIAL ILLNESS BEGINS IN THE GENITALS, BUT A ﬁrm, painless sore, known as a chancre, appears usually in the genital CAUSED BY THE HERPES SIMPLEX VIRUS, LATER CAN AFFECT OTHER BODY TISSUES. A BABY CAN region. Develops on average 21 days after exposure; lasts two to three THIS INFECTION RESULTS IN PAINFUL weeks. Progresses to secondary syphilis without treatment. BE INFECTED IN UTERO OR DURING DELIVERY. ULCERS IN THE GENITAL AREA.

The cause of syphilis is the bacterium Treponema There are two types of the herpes pallidum, which is transmitted during intercourse. simplex virus (HSV): HSV-1 usually There are three main stages; the first two being causes cold sores, while HSV-2 results Secondary syphilis infectious for up to two years and the final stage being Generalized features appear and can include fever, sore throat, swollen glands, in genital herpes. HSV is highly noninfectious. The primary stage progresses to the painful joints, rashes, and mouth and genital ulcers. Starts four to ten weeks contagious and can be passed from after initial chancre appears. Progresses to latent stage without treatment. secondary stage if treatment is not given. A latent stage person to person via sexual contact. follows, succeeded by the third stage (tertiary syphilis), HSVs can cause problems in a although this is now rare due to the availability of newborn if transferred during delivery. antibiotics. The diagnosis of syphilis is usually made The disease usually recurs, with the through a blood test, and treatment consists of antibiotic Latent syphilis first attack being the worst. Blisters injections, which can be given during pregnancy. Symptoms disappear, but blood tests show the infection is still present. develop on and around the genitals, Symptoms can recur within two years, or tertiary syphilis develops later. Condoms should be used to avoid transmission of along with tingling and soreness. the causative bacteria. The incidence of syphilis has Other symptoms include painful decreased since the introduction of penicillin. urination, vaginal discharge, and fever. The symptoms can last up to three Tertiary syphilis weeks. The diagnosis can usually be SYMPTOM STAGES Characteristic lesions, called gumma, develop mainly in the skin and Left untreated, syphilis infection progresses through in the bones, including those of the skull, leg, and collarbone. made from examination of the lesions. a series of well-defined stages (primary, secondary, The cardiovascular and nervous systems may also be affected. Treatment cannot cure the condition latent, and tertiary) on a relatively defined timescale. but may reduce its severity.

224 SEXUALLY DISEASES TRANSMITTED GENITAL WARTS GONORRHEA tubes, causing damage that may affect fertility. The diagnosis is made by testing GROWTHS IN THE GENITAL AREA CAUSED THIS COMMON SEXUALLY TRANSMITTED BACTERIAL INFECTION BY THE HUMAN PAPILLOMAVIRUS (HPV) CAUSES INFLAMMATION IN THE GENITAL AREA AND DISCHARGE swabs of the affected areas; antibiotic ARE PASSED ON VIA SKIN CONTACT. IN MEN AND WOMEN, OFTEN WITHOUT SYMPTOMS. treatment may be given intravenously if the infection has already spread. As with Genital warts can take up to 20 The bacterial cause of gonorrhea is infection but may not appear for months, other STDs, both partners are tested. An months to appear after infection. They Neisseria gonorrhoea, which is transmitted in which case infection may have spread infected woman can pass it on to her are painless and grow rapidly; they by vaginal, oral, and anal sex. Usually, around the body. Left untreated, the baby during delivery, resulting in an eye can also develop in the mouth as a symptoms appear within two weeks of infection may spread to the fallopian infection, which may cause blindness. result of oral sex. Various treatments SYMPTOMS IN MEN are available including antiviral AND WOMEN Eye infection lotions. Infection with HPV in women The main symptoms are similar with pain, increases their risk of cancer of the swelling, and in both sexes. However, in up cervix. Condoms cannot offer complete discharge to 50 percent of women and 10 percent of men, there are protection, so HPV transmission may

no symptoms whatsoever. I DISORDERS still occur. A baby can become infected Symptomless with HPV during childbirth. infection in throat Irregular vaginal bleeding

HUMAN Inﬂammation in rectum, PAPILLOMAVIRUS with pain, discomfort, This highly magniﬁed or discharge image shows human Lower papillomaviruses, the abdominal Pain or burning Green or yellow infective organisms pain or tenderness sensation on vaginal discharge responsible for urination genital warts.

CHLAMYDIA INFECTION THIS BACTERIAL INFECTION OFTEN HAS NO SYMPTOMS AND IS A MAJOR CAUSE Spherical (dark pink) OF INFERTILITY IN WOMEN. HALF OF INFECTED MEN AND 80 PERCENT OF Chlamydia bacterium INFECTED WOMEN SHOW NO SYMPTOMS, MEANING IT MAY GO UNNOTICED. inside a vaginal epithelial cell (blue) It is estimated that 5 percent or more of pneumonia. Urine samples or urethral sexually active women in the US are swabs are taken in men, and swabs infected with Chlamydia trachomatis, the of the cervix are tested in women. causative bacterium. If symptoms do Treatment is with antibiotics, some occur, they include painful urination and of which cannot be taken during discharge from the urethra in men, and pregnancy. Condoms offer protection in women, vaginal discharge, bleeding against transmission of this infection. between periods and after sex, and pain in the lower abdomen. The infection can pass up to the fallopian tubes and may CHLAMYDIA BACTERIA IN VAGINA CELLS This highly magniﬁed view of a cervical smear then cause infertility. Chlamydia trachomatis shows Chlamydia trachomatis bacteria within bacteria may be passed to a baby during the cells of the lining (epithelial cells). This delivery, causing conjunctivitis and infection is very common.

Urethra NONGONOCOCCAL URETHRITIS Inﬂammation THIS INFLAMMATION OF THE URETHRA IN MEN IS CAUSED BY AN INFECTION causes pain on OTHER THAN GONORRHEA. A COMMON STD, IT PRODUCES CHARACTERISTIC urination EFFECTS, BUT IN AROUND 15 PERCENT OF CASES THERE ARE NO SYMPTOMS.

Epididymis There are a variety of causes, including pain on urination may be accompanied Can become inflamed if Chlamydia trachomatis, Trichomonas vaginalis, by soreness and redness around the infection spreads herpes simplex virus, and Candida albicans. urethral opening, which is at the end of Nearly half of the cases of non- the penis. The infection may spread to the Penis May be painful gonococcal urethritis (NGU) identified epididymides, testes, and prostate gland. and itchy inside are caused by Chlamydia trachomatis, which In addition, certain infections may travel is the cause of chlamydia infections in in the bloodstream to cause inflammation Testis May swell if women (see above). In one-quarter and pain in the joints. Urine samples and infection spreads of cases, no cause can be found. The swabs taken from the urethra are tested NONGONOCOCCAL URETHRITIS SYMPTOMS These features are typical of NGU, although there may be condition can take up to five weeks to to look for gonorrhea and other possible no symptoms. Consequently, an infected man can pass develop after infection, but on average it infective causes. Using condoms can on the infection without being aware that he has it. takes two to three weeks. Discharge and reduce the transmission of infection.

225 COMPLICATIONS IN PREGNANCY

IN THE VAST MAJORITY OF CASES, PREGNANCY PROCEEDS WITHOUT ANY LATER, WHEN THE FETUS SEEMS TO BE DEVELOPING NORMALLY. PROBLEMS MAJOR PROBLEMS. HOWEVER, SOMETIMES A PROBLEM DOES DEVELOP, IN PREGNANCY MAY BE DUE TO FETAL FACTORS, SUCH AS A GENETIC OR AFFECTING THE MOTHER, THE FETUS, OR BOTH. FOR EXAMPLE, AN EMBRYO CHROMOSOME ABNORMALITY, OR TO MATERNAL FACTORS, SUCH AS AN MAY FAIL TO IMPLANT OR DEVELOP PROPERLY, OR A PROBLEM MAY OCCUR INFECTION, OR A HORMONAL OR ANATOMICAL PROBLEM.

MISCARRIAGE three main types of miscarriage. In a 60 threatened miscarriage, there is vaginal THIS IS THE SPONTANEOUS ENDING OF 50 bleeding but the fetus is alive and the A PREGNANCY BEFORE 24 WEEKS. MOST OCCUR DURING THE FIRST 14 WEEKS. cervix is closed. In an inevitable 40 miscarriage, the cervix is open and Early miscarriages tend to result from the fetus is usually dead. In a missed 30 a genetic or chromosomal abnormality miscarriage, the fetus has died but MISCARRIAGE RATE 20 The risk of having a in the fetus. Later miscarriages may be there is no bleeding. With a threatened miscarriage in early adult caused by a problem in the uterus. Other miscarriage, the pregnancy may proceed %) ( RISK OF MISCARRIAGE 10 life is in the region of 1 in 5 causes include cervical incompetence (see to term. An inevitable miscarriage may pregnancies (or 20 percent). below) and maternal infections. Various be complete or incomplete, meaning that 0 But as a woman ages her

COMPLICATIONS IN PREGNANCY I COMPLICATIONS DISORDERS 20–24 25–29 30–34 35–39 40–44 OVER factors increase the risk of miscarriage, some tissue remains in the uterus. An 44 risk of miscarriage increases, MATERNAL AGE (YEARS) especially over the age of 40. including smoking, drinking, and drug incomplete or missed miscarriage may abuse during pregnancy. There are require surgery to empty the uterus. CAUSES OF MISCARRIAGE THREATENED MISCARRIAGE Placenta If the cervix remains closed Miscarriage can occur as a result of main categories: inherited, hormonal, and the fetus is still alive, various underlying problems, which may immunological, infective, and the pregnancy can often Umbilical primarily be either maternal or fetal in anatomical. However, it is not always continue to term. If a cord miscarriage becomes origin. These can be classified into five possible to identify the cause. inevitable, the cervix opens so that tissue CAUSE POSSIBLE EXAMPLES can pass through. Inherited Fetal genetic or chromosomal abnormalities are possible causes, such as the presence of too many or too few chromosomes. Amniotic fluid

Hormonal Overactivity or underactivity of the thyroid gland, diabetes mellitus, and abnormally low levels of progesterone are possible causes. Blood 12-week-old clot Immunological Miscarriage can be caused by rare immune disorders, such as antiphospholipid fetus syndrome (placental clots reducing blood supply to the fetus).

Blood traveling Infective Several infections affecting the mother can cause miscarriage, from uterus including rubella and toxoplasmosis (a protozoal infection). through cervical canal Bleeding Anatomical Miscarriage can sometimes occur if the uterus is abnormally shaped evident when or has large ﬁbroids; cervical incompetence is another possible cause. via the vagina

CERVICAL INCOMPETENCE IF THE CERVIX IS WEAK (INCOMPETENT), PRESSURE FROM Suture (stitch) holds walls THE GROWING FETUS AND AMNIOTIC FLUID MAY CAUSE of cervix IT TO OPEN EARLY, RESULTING IN A MISCARRIAGE. together Weakness of the cervix may follow surgery to the cervix or a number of procedures that require the cervix to be opened (including termination of Wall of pregnancy). Cervical incompetence tends to cause cervix miscarriages after 14 weeks’ pregnancy, and often there are no symptoms before miscarriage occurs. Fetus A WEAK CERVIX If a woman has had a late miscarriage, an ultrasound If a woman has an may be arranged to check the cervix. If the ultrasound Wall of incompetent cervix, it conﬁrms cervical incompetence, a stitch may be uterus MCDONALD SUTURE can be stitched (sutured) IN PLACE inserted in the cervix at 12–16 weeks in the next together so that it Weakened cervix remains tightly closed pregnancy (and any subsequent ones) and then during pregnancy. The Vagina removed at 37 weeks ready for the start of labor. If McDonald suture shown labor begins early, the stitch is removed straight away. CROSS SECTION OF UTERUS here is commonly used.

226 COMPLICATIONS IN PREGNANCY ECTOPIC PREGNANCY p.218). Using a coil, or intrauterine which a viewing instrument is passed contraceptive device (IUD), also through the abdominal wall). If an IN AN ECTOPIC PREGNANCY, THE FERTILIZED EGG IMPLANTS OUTSIDE increases the risk. The symptoms are ectopic pregnancy is found, it will be THE UTERUS SO THAT THE EMBRYO CANNOT DEVELOP PROPERLY. THE CONDITION CAN BE LIFE-THREATENING FOR THE MOTHER. vaginal bleeding and lower abdominal removed during the laparoscopy. If an pain, usually on one side. To diagnose ectopic pregnancy leads to rupturing of In most ectopic pregnancies, the fertilized cavity. Possible underlying causes include the condition, a pregnancy test may be a fallopian tube, there will be severe egg implants in the fallopian tube, previous damage to the fallopian tube, arranged, followed by an ultrasound abdominal pain and pain in the shoulder although rarely it may implant elsewhere, perhaps due to surgery or an infection scan if the test is positive. A physician tip. The condition is potentially life- such as in the cervix, ovary, or abdominal such as pelvic inﬂammatory disease (see may also perform a laparoscopy (in threatening and requires urgent surgery.

Ampullar tubal location Isthmic tubal location

Fallopian tube

I DISORDERS Infundibular tubal location

Abdominal location X-RAY OF AN ECTOPIC Ovarian Ovary PREGNANCY location POTENTIAL LOCATIONS OF This X-ray shows an ectopic Uterus AN ECTOPIC PREGNANCY pregnancy at about 10–12 weeks This illustration shows possible in which the fetus is developing sites of an ectopic pregnancy. Most in the mother’s right fallopian Intramural location develop in the fallopian tube but they tube. Left untreated, the tube may also occur in the ovary, cervix, will rupture, causing bleeding abdomen, or in an abnormal location into the abdomen. Cervical location in the wall of the uterus.

NORMAL EMBRYO 23 chromosomes MOLAR PREGNANCY Sperm DEVELOPMENT from father THIS OCCURS WHEN A SPERM FERTILIZES AN EGG BUT THE 23 RESULTING SET OF CHROMOSOMES IS ABNORMAL SO Usually, a single egg and a single sperm, each with 23 23 THAT A NORMAL PREGNANCY CANNOT DEVELOP. 46 Normal embryo chromosomes, combine with 46 at fertilization to give a 23 23 In a complete molar pregnancy, a mass of cysts forms chromosomes normal embryo with 46 Egg 23 chromosomes in the uterus. In a partial molar pregnancy, an embryo chromosomes. from mother and placenta start to grow, but the embryo does not survive. Symptoms include vaginal bleeding, which may 23 chromosomes begin from about six weeks, and nausea and vomiting, COMPLETE MOLAR Abnormal from father PREGNANCY One sperm embryo with which may be severe. A molar pregnancy is treated by 23 A sperm with 23 23 pairs of opening the cervix (under general anesthesia) so that chromosomes fertilizes duplicated the tissue can be removed. Rarely, the an empty egg with no 23 46 paternal molar tissue becomes cancerous chromosomes. The 23 chromosomes and further treatment, such as chromosomes from the Empty egg No chromosomes sperm duplicate, giving 46. from mother chemotherapy, is necessary.

Multiple cysts develop PARTIAL MOLAR 46 chromosomes Resulting embryo within uterus PREGNANCY from father is abnormal with Two sperm, each with 23 23 23 Two sperm 69 chromosomes COMPLETE MOLAR PREGNANCY chromosomes, fertilize a 2323 The mass of cysts formed in the single egg, also with 23 69 uterus is sometimes known as chromosomes, giving an 23 23 hydatidiform mole (from Greek abnormal embryo with Egg 23 chromosomes for “grapelike”). 69 chromosomes. from mother

VAGINAL BLEEDING IN PREGNANCY ectopic pregnancy. Occasionally, light p.228), which is painful, and placenta bleeding occurs for no apparent reason previa (see p.228), which is painless. BLEEDING CAN OCCUR AT ANY TIME DURING PREGNANCY AND CAN BE DUE and the pregnancy continues. Between 14 Certain conditions, such as cervical TO A WIDE VARIETY OF CAUSES. BLEEDING AT ANY STAGE IS POTENTIALLY SERIOUS AND REQUIRES IMMEDIATE SPECIALIST ATTENTION. and 24 weeks, bleeding may signify a late polyps (noncancerous growths on the miscarriage, commonly due to cervical cervix), can cause bleeding at any time. Vaginal bleeding during the ﬁrst 14 ectopic pregnancy (see above). In some incompetence (see opposite page). Investigations of the cause may include a weeks may indicate a miscarriage (see cases, there may also be pain, which Important causes of bleeding after 24 cervical examination and an ultrasound opposite page) or, less commonly, an tends to be severe if the cause is an weeks include placental abruption (see scan. Treatment depends on the cause.

227 PLACENTA PREVIA PLACENTAL ABRUPTION IF THE PLACENTA LIES LOW IN THE UTERUS AND PARTLY OR FULLY THIS IS A POTENTIALLY LIFE-THREATENING CONDITION IN WHICH COVERS THE OPENING TO THE CERVIX, IT CAN INTERFERE WITH BIRTH. PART OR ALL OF THE PLACENTA DETACHES ITSELF FROM THE WALL THE CONDITION AFFECTS ABOUT 1 IN 200 PREGNANCIES. OF THE UTERUS BEFORE THE BABY IS BORN.

Placenta previa is a common cause of about 30 weeks for all women with There are two forms of placental An ultrasound scan will be done and painless vaginal bleeding after the 24th complete placenta previa, with a abruption: revealed abruption, a the fetal heart checked. Induction may be week of pregnancy. Heavy bleeding can cesarean section being planned for common cause of vaginal bleeding after recommended; in severe cases, emergency be potentially life-threatening for both about 38 weeks. If severe bleeding 28 weeks; and concealed abruption, cesarean section may be necessary. fetus and mother. Risk factors include occurs, an emergency cesarean section which does not cause bleeding as the a previous cesarean section, multiple is needed. A cesarean section is also blood remains in the uterus. Risk pregnancy, and several previous recommended for women with a factors include long-standing high pregnancies. It is diagnosed by an partial placenta previa. blood pressure, a previous abruption,

COMPLICATIONS IN PREGNANCY COMPLICATIONS ultrasound scan. Often, the placenta will and several previous pregnancies.

move up as the uterus grows, but if it PLACENTAL POSITIONS Smoking, excessive drinking, and drug In placenta previa, the position of the stays low and bleeding occurs, admission placenta varies from lying low in the uterus abuse also increase the risk. In contrast to the hospital is necessary. Hospital without encroaching on the cervix to lying to bleeding in placenta previa, a admission may be recommended from centrally across the cervix. placental abruption is always painful and causes the uterus to contract. Amniotic DISORDERS I DISORDERS ﬂuid Wall of uterus PLACENTAL DETACHMENT Blood In most cases, the placenta becomes partly Placenta detached, and blood detaches either passes out through from uterine the vagina or collects wall Placenta sits Wall of Low-lying Placenta covers between the placenta centrally over and uterine wall. Rarely, Cervical uterus placenta part of cervix cervix MARGINAL PARTIAL COMPLETE the entire placenta may mucus plug PLACENTA PREVIA PLACENTA PREVIA PLACENTA PREVIA become detached.

AMNIOTIC FLUID PROBLEMS CAUSES OF AMNIOTIC FLUID PROBLEMS THE AMOUNT OF FLUID CONTAINED IN THE AMNIOTIC SAC CAN BE AFFECTED BY A NUMBER OF CONDITIONS, RESULTING IN EITHER AN ABNORMALLY LARGE VOLUME Excessive amniotic ﬂuid (polyhydramnios) or too little (POLYHYDRAMNIOS) OR AN ABNORMALLY SMALL VOLUME (OLIGOHYDRAMNIOS). (oligohydramnios) may be associated with factors in the mother or the fetus. Some common factors are below. Polyhydramnios can cause maternal discomfort complications for mother and fetus. Where and is associated with premature rupture of the possible, the underlying causes are treated. CAUSES OF CAUSES OF membranes and premature labor. Polyhydramnios Oligohydramnios is often only noticed during OLIGOHYDRAMNIOS POLYHYDRAMNIOS also increases the risk of placental abruption (see prenatal checks. This condition, caused by Premature rupture of membranes Diabetes mellitus above), postpartum hemorrhage (see p.240), the premature rupture of the membranes, is cesarean section, and unstable lie (where the fetal associated with premature labor and fetal growth Fetal growth restriction, for Gastrointestinal (bowel) position is constantly changing). The condition is restriction (see opposite). Regular assessment of example due to preeclampsia obstruction managed to prolong the pregnancy and prevent fetal well-being should be performed.

25 A fetal abnormality causing Impaired fetal swallowing due Too much reduced urine production to fetal abnormalities, such as amniotic ﬂuid or obstruction of passage anencephaly 20 (polyhydramnios) of urine

The use of drugs, such as Heart failure due to congenital 15 nonsteroidal anti- reasons or anemia inﬂammatory drugs Normal range of amniotic ﬂuid Twin–twin transfusion Increased fetal urine production 10 syndrome (an imbalance (such as twin–twin transfusion when one twin receives syndrome)

AMNIOTIC FLUID INDEX (cm) AMNIOTIC more blood than the other) Too little 5 amniotic fluid (oligohydramnios) Infection Infection, such as syphilis or parvovirus 0 14 18 22 26 30 34 38 42 Chromosomal abnormalities, Chromosomal abnormalities, GESTATIONAL AGE (WEEKS) KEY such as Down syndrome such as Down syndrome CHECKING THE AMOUNT OF AMNIOTIC FLUID 95TH CENTILE An amniotic fluid index chart can indicate whether the amount Postmaturity—a baby is overdue Achondroplasia (a bone 50TH CENTILE of fluid is within normal limits. The 50th centile line shows the disorder causing short stature) “average” amount; 5th and 95th centiles show the normal limits. 5TH CENTILE

228 COMPLICATIONS IN PREGNANCY FETAL GROWTH RESTRICTION ALSO KNOWN AS INTRA-UTERINE GROWTH RETARDATION, THIS CONDITION 5 OCCURS WHEN A FETUS FAILS TO GROW SUFFICIENTLY IN THE UTERUS SO THAT 97th centile IT IS THIN AND HAS A LOW BIRTH WEIGHT (LESS THAN 51/2 LB/2.5 KG). 4 50th centile

Fetal growth restriction has many possible causes, umbilical artery, are used to monitor fetal growth. 3 including long-standing high blood pressure, Hospital admission for bed rest and monitoring may preeclampsia (see below), or a maternal infection, such be needed, and, when possible, any underlying causes 2 as rubella. In some cases, it may occur because the are treated. An early delivery may be recommended WEIGHT (KG) placenta fails to supply sufﬁcient nutrients to the fetus. if there are concerns about the baby’s health. 1 3rd centile Inherited fetal disorders, such as Down syndrome, are also possible causes. The risk of growth restriction is MONITORING FETAL GROWTH 0 This graph shows fetal weight-increase curves in pregnancy; 22 26 30 34 38 42 increased if the mother has a poor diet, smokes, drinks the 97th centile and 3rd centile lines show the upper and lower GESTATIONAL AGE (WEEKS) excessively, or abuses drugs. Repeat ultrasound scans, limits of the normal range. If weight begins to fall below the

KEY NORMAL NORMAL GROWTH- I DISORDERS and sometimes Doppler scans of blood ﬂow in the lower limit, fetal growth restriction is indicated. BABY SMALL BABY RESTRICTED BABY

Length of femur Wall of uterus Fetus in third trimester The fetal heart BLOOD FLOW IN produces a wave of Period of no UMBILICAL ARTERY flow in the blood flow signals A Doppler ultrasound umbilical artery a problem shows blood flow in the arteries carrying blood from the fetus to the placenta. An abnormality may indicate a problem in the fetus or placenta.

Abnormal dip Rise as heart Dips as heart in blood flow contracts relaxes BLOOD FLOW IN UTERINE ARTERY The uterine artery carries blood to the uterus. Blood flow MEASURING THE LENGTH OF THE FEMUR through the artery Cervical The femur (thighbone) can be measured from indicates the amount Fetal foot Amniotic mucus ultrasound images. This measurement can be taken fluid plug of blood getting to at intervals and, together with the abdominal CROSS SECTION the placenta and then circumference, used to monitor fetal growth. THROUGH THE UTERUS on to the fetus.

PREECLAMPSIA AND Visual disturbance Severe headache RISK FACTORS FOR PREECLAMPSIA Flashing lights, blurry Commonly ECLAMPSIA vision, and sensitivity experienced at the The underlying cause of preeclampsia is not yet fully THESE CONDITIONS ARE UNIQUE TO to light are common front of the head understood, although it may be due to a problem PREGNANCY AND ALWAYS IMPROVE with the placenta. However, various risk factors have FOLLOWING DELIVERY OF THE BABY. Nausea and vomiting been identified that increase the likelihood of In preeclampsia, the blood pressure May be developing the condition, and these are listed below. increases, fluid is retained, and protein experienced is lost in the urine. Symptoms occur alongside some dizziness Being overweight or obese quite late in the condition, including Abdominal pain swelling of the hands, face, and feet, This pain tends to occur in the A family or personal history of preeclampsia headache, visual disturbances, and center of the Sudden abdominal pain. If untreated, high upper part of weight gain the abdomen A multiple pregnancy blood pressure leads to eclampsia Unusually fast (seizures) in 1 percent of women with weight gain (more First pregnancy or first pregnancy with than 2 lb (0.9 kg) a new partner preeclampsia. For this reason, every a week) pregnant woman has her urine checked Ten years or more have passed since the last pregnancy for the presence of protein and her blood pressure measured at each Being over the age of 35 prenatal visit. Treatment aims to return the blood pressure to within the normal PREECLAMPSIA SYMPTOMS Preexisting kidney disease range. There may be fetal growth Preeclampsia may be mild and restriction (see above) and hospital produce no symptoms. Sudden edema Preexisting high blood pressure monitoring, and early delivery of the In many cases, symptoms do Sudden swelling of the feet (and/ baby may be necessary. Eclampsia develop, affecting various parts of the body. Severe or face or hands) Preexisting diabetes mellitus is a sign of is treated urgently and delivery by symptoms may herald preeclampsia cesarean section usually follows life-threatening eclampsia. Certain autoimmune disorders once the mother has been stabilized.

229 GESTATIONAL DIABETES HYPEREMESIS WHEN DOES MORNING SICKNESS DIABETES MELLITUS CAN DEVELOP IN PREGNANCY IF THE GRAVIDARUM BECOME HYPEREMESIS GRAVIDARUM? PANCREAS CANNOT MEET THE INCREASED NEED FOR THE VOMITING IN EARLY PREGNANCY BLOOD-GLUCOSE-REGULATING HORMONE INSULIN. MORNING HYPEREMESIS CAN BE SO SEVERE THAT NO FLUIDS SICKNESS GRAVIDARUM OR FOOD CAN BE KEPT DOWN. Gestational diabetes often causes no symptoms, but if they There is little, if any, loss A significant amount of weight do occur they may include excessive thirst, tiredness, and In contrast to women with normal of weight. In fact, there is —5–20 lb (2.2–9 kg) or sometimes passing large amounts of urine. It is diagnosed by blood morning sickness, who gain weight, usually weight gain. even more—is lost. tests. Treatment is by dietary control and, in a few cases, those with hyperemesis gravidarum insulin injections. The baby lose weight and may also become Nausea and vomiting do Nausea and vomiting result THE CONSEQUENCES OF may grow very large, which dehydrated. The cause is not fully not interfere with the in a poor appetite and GESTATIONAL DIABETES may necessitate a cesarean understood, but very high levels ability to eat and drink. dehydration. The typical result is a large baby. The mother’s section. Gestational diabetes of the hormone human chorionic insulin and glucose usually usually disappears after the gonadotropin (hCG), produced in Vomiting is infrequent, and Vomiting is frequent and may normalize after the birth. birth but may recur. pregnancy, may play a role. Having nausea tends to be episodic contain bile or blood. Nausea is and mild. constant and moderate to severe. twins is associated with high levels A woman with gestational diabetes has poorly controlled blood of hCG and an increased risk of glucose levels because insulin is not being made in sufficient hyperemesis gravidarum. Stress may Dietary and lifestyle changes Intravenous fluid amounts. Consequently, her blood glucose levels are high. are usually all that is required rehydration and antinausea also worsen the condition. If the to improve well-being. medicine are necessary. vomiting is extremely severe, hospital COMPLICATIONS IN PREGNANCY I COMPLICATIONS DISORDERS admission may be arranged, where Typically, improvement is seen Symptoms may wane during This blood high in glucose passes to the baby via the placenta. blood tests will be done to assess the Blood glucose is the baby’s main food source. after the first trimester, but mid-pregnancy but nausea and level of dehydration and ultrasound queasiness may occur at times. vomiting may continue. used to check the fetus. Intravenous fluids and antinausea drugs may be Usual tasks, such as work and The mother may be unable to The baby increases insulin production to utilize this glucose; given. The condition usually clears up looking after children, are work for weeks or months and unused glucose is laid down as fat. Consequently, the baby grows larger than normal, which may pose problems during delivery. by about the 14th week of pregnancy possible on most days. may need to be cared for. but may recur in future pregnancies.

RHESUS INCOMPATIBILITY against the Rh-positive blood cells. This prior to 37 weeks; in more severe cases, it does not cause problems in the ﬁrst may be as early as 26 weeks. If a fetus is A MISMATCH BETWEEN THE RHESUS BLOOD GROUP OF A FETUS AND pregnancy, but if the woman has a too ill or immature to be delivered, it may THE MOTHER CAN RESULT IN PROBLEMS IN A FUTURE PREGNANCY IF THE SAME MISMATCH OCCURS. Rh-positive baby again, her antibodies if be given a transfusion of Rh-negative formed will cross the placenta and destroy blood. Antibody injections are given to Blood is classed as Rh positive or Rh Rh-negative woman has a Rh-positive fetal red blood cells. This will cause the mother during each pregnancy to negative depending on whether the red partner, she may have a Rh-positive baby. anemia in the fetus and jaundice (see destroy any fetal blood cells that enter her blood cells have Rhesus proteins on their The baby’s Rh-positive cells may trigger p.235) after birth. In mild cases of Rhesus circulation, thereby preventing antibody surface or not (Rhesus status). If an the formation of antibodies in the mother incompatibility, labor may be induced formation, and prevent this complication.

RH-NEGATIVE MOTHER RH-POSITIVE FATHER Gene version Fetal blood is Mother’s blood is Fetal blood enters Anti-Rhesus Antibodies for Rhesus Rh positive Rh negative mother’s bloodstream antibody cross placenta positive Gene version for Rhesus negative

RH-POSITIVE RH-NEGATIVE RH-POSITIVE RH-NEGATIVE CHILD CHILD CHILD CHILD

RH-NEGATIVE MOTHER RH-POSITIVE FATHER

Rh-positive fetus THE FIRST PREGNANCY DURING CHILDBIRTH THE NEXT 1An Rh-negative mother will 2 Leakage of fetal red blood 3 PREGNANCY not have incompatibility cells into the mother’s circulation The mother’s antibodies RH-POSITIVE CHILDREN problems with an Rh-positive during childbirth will cause her move freely across the HOW RHESUS STATUS IS PASSED DOWN baby. Problems arise in later to produce antibodies. These placenta and destroy Every person has two versions of the gene for Rhesus pregnancies if the mother is antibodies will react against Rh-positive fetal red blood (Rh) status. If one is the Rh-negative version and the Rh negative and the fetus Rh-positive red blood cells in any cells, which causes anemia other Rh-positive, the Rh-positive version will prevail. Rh positive. subsequent pregnancies. in the fetus.

230 COMPLICATIONS IN PREGNANCY

Red blood cells URINARY TRACT E. coli bacteria Mucus filaments result from CARPAL TUNNEL INFECTIONS cover bladder’s secreted by bleeding caused SYNDROME interior surface epithelial cells by infection BACTERIAL INFECTIONS OF THE URINARY THIS TINGLING, NUMBNESS, AND PAIN IN TRACT ARE COMMON DURING PREGNANCY THE HAND IS DUE TO COMPRESSION OF DUE TO THE DELAYED CLEARING OF URINE. A NERVE IN THE WRIST. Hormonal changes in pregnancy and Swollen One of the nerves to the hand passes the enlarged uterus delay the urine flow, epithelial through a small gap (the carpal tunnel) cells line which makes pregnant women susceptible bladder between the wrist bones and the to urinary infections. Symptoms include ligament over them. In pregnancy, a burning sensation when urinating, swelling of the tissues can reduce this frequent urination, and pain in the lower gap, compressing the nerve and INSIDE A BLADDER abdomen, lower back, or on one side. causing tingling, numbness, and The bacterium E. coli Fever and pain in the kidney area may is a common cause of sometimes pain in the hand. Bending I DISORDERS indicate that the infection has spread up urinary tract infections and straightening the wrist and fingers the urinary tract. A urine test may be in pregnancy, causing may help relieve the symptoms. The done to confirm the diagnosis; treatment swelling of the condition usually clears up after epithelial cells of the is with antibiotics. Untreated, a urinary bladder lining and, delivery, but sometimes surgery may tract infection may lead to premature sometimes, red blood be needed to release pressure on the labor or a low-birthweight baby. cells in the bladder. nerve and relieve the symptoms.

SCIATICA EDEMA disappear during the night after lying in bed and then gradually worsens through THIS PAIN SPREADS FROM THE BUTTOCK SWELLING DUE TO FLUID BUILDUP IS the day. It may be improved by raising DOWN THE BACK OF THE LEG DUE TO COMMON IN PREGNANCY. THE FEET, PRESSURE ON THE SCIATIC NERVE. LEGS, AND HANDS MAY BE AFFECTED. the legs when sitting and by staying mobile—for example, by walking or The changes in posture during pregnancy Fluid retention is particularly common swimming—which aids the circulation; can put pressure on the sciatic nerve, in the last few months of pregnancy, support hose can also be helpful. The which runs down the back of the leg affecting up to 80 percent of healthy fluid retention is usually no cause for and divides at the knee to go to the outer pregnant women. The accumulated concern, although it may occur as a border and sole of the foot. In addition to fluid causes swelling, which tends to symptom of preeclampsia (see p.229). pain, sciatica may also make it difficult to stand upright, and even to walk if the Pressure causes depression condition is severe. The symptoms tend in skin that disappears only to be intermittent and usually clear up gradually when presssure is removed after birth. In the meantime, they may be alleviated by adopting good posture, with the shoulders pulled back, the SWOLLEN FOOT Fluid usually accumulates first in the feet spine kept straight, the bottom tucked and, if severe, may extend up the leg; the under, the abdomen tucked in, and the hands may also be affected. Pressing the knees kept relaxed. swelling causes a long-lasting depression.

Sciatic nerve runs from buttock down back of thigh and divides at knee to supply foot PROBLEMS SPECIFIC TO MULTIPLE PREGNANCIES

THE COURSE OF THE SCIATIC NERVE A multiple pregnancy increases the risk of problems for the mother and her babies. The sciatic nerve, the largest nerve in the body, is The normal complaints, such as morning sickness, are often worse due to the formed when nerves from the lower spine combine higher hormone levels and the larger uterus. There is also an increased risk of to form one thick nerve. The nerve and its branches developing medical problems, such as iron-deficiency anemia, high blood pressure, extend along the length of the leg. preeclampsia (see p.229), hyperemesis gravidarum (see opposite), placenta previa (see p.228), polyhydramnios (see p.228), and miscarriage (see p.226). Babies VARICOSE VEINS leaky. As a result, blood builds up in tend to be small, and premature labor superficial veins, which drain into the is more likely. A multiple pregnancy SWOLLEN VEINS IN THE LEGS MAY DEVELOP deep veins, causing the superficial OR WORSEN DURING PREGNANCY DUE TO requires special monitoring but most PRESSURE FROM THE ENLARGED UTERUS. veins to become swollen and distorted have a good outcome. (varicosed). The problem may be In the later stages of pregnancy, the helped by keeping mobile, raising the enlarged uterus places pressure on the legs when sitting, and wearing support THREE IN A WOMB Triplets occur in only 1 in 8,000 births. deep veins that carry blood away from hose. Injection therapy and surgery Multiple pregnancies from assisted the legs, causing the valves that normally may be options after pregnancy, if conception are now less common due to prevent backflow in them to become treatment is required. restrictions on the number of embryos used.

231 LABOR AND DELIVERY PROBLEMS

FOR MANY WOMEN, LABOR AND DELIVERY ARE UNPROBLEMATIC, INTENSE, SIGNS OF DISTRESS OR BECOME STUCK AND NEED URGENT DELIVERY. AND JOYFUL. BUT FOR SOME, PROBLEMS ARISE EITHER FOR THE FETUS OR FROM THE MOTHER’S POINT OF VIEW, TISSUES AROUND THE VAGINAL FOR THE MOTHER. FOR INSTANCE, LABOR SOMETIMES STARTS BEFORE OPENING CAN TEAR DURING CHILDBIRTH AND SOMETIMES AN ASSISTED PREGNANCY HAS REACHED ITS FULL TERM, OR THE FETUS MAY SHOW DELIVERY MAY RESULT IN INJURY.

PREMATURE LABOR FETAL DISTRESS fetal heart rate usually fluctuates, with marked increases with maternal contractions). Possible causes include THIS TERM DESCRIBES LABOR THAT BEGINS BEFORE PARTICULAR SIGNS INDICATE WHEN A FETUS IS placental abruption (see p.228), but a cause may not be 37 WEEKS. BABIES BORN PREMATURELY MAY HAVE NOT WELL OR IS NOT RESPONDING AS NORMAL ASSOCIATED COMPLICATIONS (SEE P.234). OR EXPECTED DURING PREGNANCY OR LABOR. found. If necessary, the baby is delivered immediately either vaginally or by cesarean section. Causes of early labor include multiple pregnancy Fetal distress may be suggested by reduced fetal and maternal infections. Often no reason is found. movements felt by the mother, meconium (fetal USING CARDIOTOCOGRAPHY TO Several factors can increase the risk, including feces) in the amniotic fluid, and problems with the MONITOR FETAL WELL-BEING Cardiotocography records the fetal heart rate and smoking or drinking alcohol when pregnant, stress, fetal heart rate, which may be faster than it should be frequency of maternal contractions continuously. The and a previous premature labor. Tightenings in the (tachycardia), slower than it should be (bradycardia), heart rate should rise briefly with each contraction, abdomen, normally painless become painful and or not showing as much variability as it should (the which can be checked on the printed traces. LABOR AND DELIVERY PROBLEMS I LABORDISORDERS AND DELIVERY regular with bloody mucus discharge and pains 200 in the lower back. If the onset of labor is very 180 Abnormally high premature, the doctor may try to halt its progress fetal heart rate with drugs given to the mother intravenously. If 160 this is not possible, she may be given corticosteroid 140 Normal range of injections to help the fetal lungs mature. Premature fetal heart rate 120 babies, depending on how early they arrive, may need care in a special unit while their organs mature. 100 Abnormally low 80 fetal heart rate 60

FETAL HEART RATE (BEATS PER MINUTE) (BEATS RATE HEART FETAL 132 4951617180121314151617181920 TIME (MINUTES) PREMATURE TRIPLETS Women who have Mother’s uterine multiple pregnancies contractions are more likely to go recorded at the same time as

into labor early. It OF STRENGTH CONTRACTION fetal heart rate may be because the uterus is overly 132 4951617180121314151617181920 stretched. TIME (MINUTES)

CORD PROLAPSE RETAINED THIS EMERGENCY SITUATION ARISES WHEN THE UMBILICAL CORD APPEARS PLACENTA THROUGH THE CERVIX BEFORE THE PRESENTING PART OF THE FETUS (THE PART SOMETIMES THE PLACENTA OR NEAREST THE CERVIX), WHICH CAN COMPROMISE ITS BLOOD SUPPLY. MEMBRANES DO NOT DETACH FROM THE WALL OF THE UTERUS AS THEY SHOULD Cord prolapse usually occurs during amniotic ﬂuid (polyhydramnios, see AFTER THE BABY HAS BEEN DELIVERED. labor, but occasionally it happens when p.228). It is essential for the mother to the waters break during pregnancy. The move into the correct position (see A retained placenta may occur for a fetus may compress the cord, reducing below) if a cord prolapse is present. An number of reasons, including uterine the blood supply it receives. A cord urgent vaginal delivery may be possible atony (the uterus stops contracting as prolapse may occur when a fetus is not (if necessary using forceps or vacuum it should to expel the placenta) or the engaged (see p.189), when it is not suction) if the cervix is fully dilated; uncommon condition placenta accreta, head-down (particularly if it is lying otherwise an emergency cesarean present when part of the placenta across the uterus), when there is section will be performed immediately. cannot detach itself because it is a multiple pregnancy, or deeply embedded in the uterine Placenta when there is excess wall. If part or all of the placenta or Compressed cord Uterus membranes are retained, the uterus RELIEVING PRESSURE cannot contract effectively so that The mother kneels on all Umbilical cord fours. The physician or within cervix bleeding from the uterine blood midwife may insert a hand vessels persists. If the placenta remains into the vagina to hold the BABY PRESSING ON CORD stuck in the uterus, it will need to be baby away from the If the baby presses on the umbilical cord, delivered by hand, using a regional umbilical cord. compressing the blood vessels it contains, it can reduce the ﬂow of blood, and anesthetic (epidural or spinal, see oxygen, from the placenta to the baby. pp.196–97) or a general anesthestic.

232 LABOR AND DELIVERYLABOR PROBLEMS SHOULDER DYSTOCIA GROUP B THIS MEDICALLY URGENT SITUATION ARISES WHEN A BABY’S HEAD IS DELIVERED BUT STREP TRANSFER ONE OF ITS SHOULDERS GETS STUCK BEHIND THE PUBIC SYMPHYSIS, THE JOINT AT THIS BACTERIAL INFECTION CAN CAUSE PROBLEMS THE FRONT OF THE MOTHER’S PELVIS. FOR A NEWBORN IF IT IS TRANSFERRED FROM MOTHER TO BABY DURING PREGNANCY OR DELIVERY. Shoulder dystocia occurs unexpectedly during a normal position to make more room for the baby to come vaginal delivery or an assisted delivery (helped by out. He or she may press on the lower abdomen to Group B streptococcus is present normally in forceps or vacuum suction, see p.202). It causes problems dislodge the shoulder and may also try to reposition the intestine and vagina of many women (up to because the baby cannot start to breathe and it may the baby vaginally. An episiotomy may be made about one-third). In some of these women, the compress the umbilical cord. This is an emergency to provide more room for the delivery. Shoulder infection will be transferred to the fetus either situation. The physician or midwife asks the mother to dystocia may result in damage to the network of in utero or during the delivery. Certain factors stop pushing and may also ask her to change her nerves that supply the arm (the brachial plexus). increase the risk of passing the bacteria on to the baby, such as premature labor (that is, before Pubic symphysis This slightly ﬂexible joint 37 weeks) or a urinary tract infection caused by between the front sides of Group B streptococcus. Symptoms in an affected I DISORDERS the pelvis opens slightly baby may include fever, breathing problems, during pregnancy. problems with feeding, and ﬁts. Babies may Baby’s shoulder have blood tests to detect the infection, which The shoulder becomes is treatable with antibiotics. stuck behind the mother’s pubic symphysis.

CEPHALOPELVIC Crowning DISPROPORTION Once the head Sometimes a baby cannot Vulnerable area appears, the body be delivered vaginally GROUP B STREPTOCOCCAL CHAINS The brachial nerve plexus, should easily because it is very large, These bacteria, which can be present in the which supplies the arm, might follow, but this the mother’s pelvis is too bowel and others areas in healthy adults be damaged during delivery of is delayed in narrow, or a combination without causing any problems, can have very a baby with shoulder dystocia. shoulder dystocia. of the two. serious effects if transferred to a newborn.

Vagina PERINEAL TEARS Most tears begin at the CLASSIFICATION OF WHEN TISSUES UNDERGO EXTREME border of the vagina, PERINEAL TEARS STRETCHING AS A BABY PASSES DOWN THE caused by extreme stretching of tissues. BIRTH CANAL, TEARS CAN OCCUR BETWEEN DEGREE DETAILS OF INVOLVEMENT THE VAGINAL OPENING AND THE ANUS. Fourchette This fold of tissue First The most common tears, these Tears may range from a tiny one connecting the labia affect skin and tissues around the involving the edge of the vaginal may be torn. vaginal opening but no muscles are opening to those that involve deeper involved. They may need stitches or may heal themselves. layers of muscle or extend to the anus. Labia majora Small tears may also occur in the upper Rarely, tears may Second When muscle around the vagina is vagina. Rarely, the cervix or the labia involve folds of skin involved, tears tend to be quite are involved. A number of factors put that surround the sore. Dissolvable stitches are used women at increased risk of a tear, vaginal opening. to repair the layers, and healing takes a few weeks. including a ﬁrst vaginal delivery, a previous severe tear, an assisted delivery, Perineum Third Vaginal tissue, perineal skin, and a big baby, or a baby facing forward The area between muscles beneath, as well as muscle rather than downward. Sometimes, the vagina and the anus around the anus (anal sphincter), is involved in more are involved in a third-degree tear. episiotomy cuts (see p.202) tear further. serious tears. All layers need stitching. Stitches may be needed to bring the torn layers of a tear back together to heal. Anus Fourth When a third-degree tear extends The muscle around into the tissues beneath the anal TISSUES INVOLVED IN PERINEAL TEARS the anus and, sphincter, it becomes a fourth- Tears can extend from the edge of the vagina occasionally deeper degree tear. Many stitches are toward the anus. If tears extend to the deeper tissues, may be torn. needed to reposition all the tissues. tissues, they may take some weeks to heal.

233 PROBLEMS IN NEWBORNS

NEWBORN BABIES ARE AT RISK OF VARIOUS ILLNESSES, SUCH AS INFECTIONS DELIVERY—OR OCCUR FOR NO OBVIOUS REASON. PEDIATRICIANS ARE SKILLED PASSED ACROSS THE PLACENTA OR DURING BIRTH. THESE ILLNESSES MAY ARISE IN MANAGING THESE CONDITIONS, WHICH SOMETIMES REQUIRE CARE AS A RESULT OF PREMATURE BIRTH OR PROBLEMS DURING PREGNANCY OR IN A NEONATAL INTENSIVE CARE UNIT.

PREMATURE BIRTH COMPLICATIONS Premature babies are particularly susceptible to certain medical distress syndrome (see lung problems, below). Continuing problems, especially if they are born very early or have a very low advances in the management of premature babies have improved birth weight. This is because they have had less time to develop; the outlook for them, but nevertheless they are still at increased this lack of maturity can be seen particularly clearly in respiratory risk of certain chronic problems that require long-term treatment.

PROBLEMS IN NEWBORNS I PROBLEMS DISORDERS LUNG PROBLEMS RETINOPATHY OF PREMATURITY PREMATURITY IS ASSOCIATED WITH A NUMBER OF RESPIRATORY PROBLEMS IN THE THIS CONDITION (OFTEN SIMPLY CALLED ROP) AFFECTS THE DEVELOPMENT OF BLOOD NEWBORN BABY, SUCH AS RESPIRATORY DISTRESS SYNDROME AND EPISODES IN WHICH VESSELS IN THE RETINA, THE INNERMOST LAYER OF THE EYE THAT CONTAINS LIGHT- THE BABY’S BREATHING IS ABNORMALLY SLOW OR EVEN STOPS COMPLETELY. SENSITIVE CELLS AND NERVE CELLS THAT SEND MESSAGES TO THE BRAIN TO FORM IMAGES.

Respiratory distress syndrome is most This condition affects about 20 percent likely to affect babies born before 28 of very low birth weight babies who are weeks’ gestation. It is due to lack of a born before 31 weeks’ gestation. There substance called surfactant, which helps is abnormal development of the retinal to keep the lungs’ tiny air sacs (alveoli) blood vessels, which grow excessively open. As a result, the surface area in some areas of the retina but do not of the lungs is reduced, causing the reach others. The abnormal vessels baby’s breathing to be labored and the are fragile and can leak, damaging the breathing rate to be higher than normal. retina and impairing vision. In severe If a premature birth is anticipated, cases, the condition may progress to steroids may be given to the woman detachment of the retina from the during pregnancy to help the baby’s underlying tissue layers and loss of lungs mature. After delivery, surfactant BREATHING ASSISTANCE vision. ROP is diagnosed and assessed may be given directly into the baby’s A premature baby may need help with by imaging the retina. Mild cases may breathing, either to keep the airways open or lungs through a tube. A chest X-ray clear up by themselves, but in more to take over breathing while the lungs mature. may be taken to conﬁrm the diagnosis. severe cases, laser treatment may be Oxygen is given, and assisted ventilation baby. Episodes of slow or absent needed to reduce visual impairment. may be needed, either in the form of breathing are also common in premature IMAGING THE RETINA CPAP (continuous positive airways infants. Possible causes include low Premature babies can be checked for pressure), which maintains the pressure oxygen levels or low blood-sugar levels, retinopathy using a retinal camera (shown in the airways between breaths, or but in many cases no cause can be here being demonstrated on a doll). mechanical ventilation, in which a found. A respiratory stimulant drug may machine takes over breathing for the be needed, and, in some cases, CPAP. Ridge of scar tissue forms, which can cause retinal detachment in later stages of the condition

BRAIN HEMORRHAGE Lens Retinal blood vessels fail BLEEDING INTO THE BRAIN IS COMMON IN VERY PREMATURE BABIES, USUALLY to reach periphery and Iris OCCURRING WITHIN THE FIRST 72 HOURS AFTER THE BIRTH. THE PROBLEMS CAUSED multiply abnormally VARY GREATLY, DEPENDING ON THE SEVERITY AND SITE OF THE BLEEDING. Retina Brain hemorrhages are more common in babies with severe respiratory distress syndrome (see above) and EYE WITH RETINOPATHY those who have been deprived of oxygen around the OF PREMATURITY time of birth. Some hemorrhages may result in cerebral HEALTHY EYE palsy (see opposite page), in which problems arise from damage to the brain’s nerve tissue and a buildup of fluid in the brain (hydrocephalus). CT or ultrasound BLOOD VESSEL scanning is used to assess the location and size of the DEVELOPMENT hemorrhage. With hydrocephalus, excess fluid may be In retinopathy of removed or a permanent prematurity some BLEEDING IN THE BRAIN shunt may be inserted that areas of the retina Retinal In this CT brain scan of a do not have blood blood diverts the excess fluid preschool child, there is partial vessels and so do not vessels Blood vessels disappearance of the brain from the brain into the receive the oxygen and reach retina’s cavities due to a hemorrhage. abdomen. nutrients they need. periphery

234 PROBLEMS IN NEWBORNS MEDICAL CONDITIONS What happens to babies during pregnancy, delivery, and the time can cause problems, as can excessive drinking by the mother during soon after birth affects their health. Certain infections passed to pregnancy. Damage to the brain at or around delivery can cause a baby during pregnancy or on the journey down the birth canal cerebral palsy. Jaundice is another common problem in the newborn.

NEONATAL JAUNDICE CONGENITAL INFECTIONS A COMMON SYMPTOM IN NEWBORN BABIES, JAUNDICE IS A YELLOW THESE ARE INFECTIONS THAT A BABY HAS WHEN IT IS

COLORATION OF THE SKIN AND WHITES OF THE EYES. THIS IS USUALLY BORN, WHICH HAVE BEEN TRANSFERRED FROM THE I DISORDERS CONSIDERED NORMAL AND CLEARS UP BY ITSELF IN A FEW DAYS. MOTHER EITHER IN PREGNANCY OR DURING DELIVERY.

Jaundice is due to high levels of the pigment bilirubin, which is formed In early pregnancy, fetal development may be disrupted naturally in the body. The liver, which normally disposes of bilirubin, by infections such as rubella, which can cause heart may not function properly at ﬁrst, causing bilirubin levels to rise, but defects. Some infections in early pregnancy can also lead this usually corrects itself in a few days, although phototherapy may to miscarriage. Later in pregnancy, certain infections may be needed. Occasionally jaundice may be due lead to premature labor and illnesses in the newborn. PHOTOTHERAPY to an underlying problem, such as Rhesus Infections that can be passed on during delivery include A newborn baby is given incompatibility (see p.230), an infection, or streptococcus and herpes. Preventive measures include light therapy, during which the light waveform a liver abnormality. In such cases, jaundice immunization against rubella and taking care with food breaks down bilirubin, may be severe and, if left untreated, may hygiene. Cesarean section may be recommended for reducing the jaundice. affect hearing and brain function. some women, including those with HIV or genital herpes.

FETAL ALCOHOL SYNDROME Flat midface DRINKING TOO MUCH ALCOHOL IN PREGNANCY MAY LEAD TO FETAL High-arched ALCOHOL SYNDROME, WITH FEATURES INCLUDING HEART PROBLEMS, eyebrows LEARNING DIFFICULTIES, AND CERTAIN DISTINCTIVE FACIAL FEATURES. Eyelid droop The features of fetal acohol syndrome (FAS) vary from Small eyes (ptosis) one individual to another but typically include reduced Skin folds growth, developmental delay, heart abnormalities, and Saddle-shaped under eyes nose the presence of certain facial characteristics. Diagnosis of the condition is based on the features present. Smooth, Affected children may require surgery to treat Low-set indistinct heart defects and special help at school for ears philtrum learning difﬁculties. There are also often (the groove Corpus callosum between nose behavioral problems. The syndrome CHARACTERISTIC FACIAL FEATURES and upper lip) MRI SCAN OF CHILD’S BRAIN is a lifelong condition, and affected Children affected by fetal Thin upper lip The corpus callosum (colored purple), which individuals may be unable to live alcohol syndrome tend to have connects the two hemispheres of the brain, is independently later in life. characteristic facial features. Short jaw (micrognathia) commonly affected in fetal alcohol syndrome.

Areas of brain Area of brain CEREBRAL PALSY damage damage CONGENITAL THIS MOVEMENT DISORDER OCCURS AS A Oxygen-poor HYPOTHYROIDISM RESULT OF BRAIN DAMAGE BEFORE, DURING, blood to Blood IN A BABY BORN WITH AN UNDERACTIVE OR IN THE EARLY YEARS AFTER BIRTH. clot brain THYROID GLAND, INSUFFICIENT THYROID HORMONES ARE PRODUCED. Cerebral palsy may occur for no apparent reason or it may result from a congenital Thyroid hormones regulate the body’s infection (see above) or from oxygen metabolism. Symptoms of deficiency deprivation during birth. Very premature tend to be noticed only as the child gets babies are particularly at risk because older. They include a failure to grow they are prone to bleeding into the brain. and put on weight, feeding problems, Meningitis or a head injury in early life prolonged jaundice, dry, mottled skin, can also be a cause. Symptoms only tend a large tongue, and a hoarse cry. There to become apparent after several months, are also learning difficulties. Screening and may include limb weakness, lack is carried out on all newborn babies of control of movement, swallowing so that treatment can be started as early problems, developmental delay, and as possible to prevent problems from vision and hearing problems. About a OXYGEN STARVATION STROKE IN A developing. Treatment is with thyroid quarter of affected children have learning AT BIRTH NEWBORN hormone supplements and is lifelong. If the brain is deprived of oxygen If a clot deprives one brain area difficulties. Cerebral palsy is lifelong but during birth, there will be generalized of blood, damage is localized In most cases, children treated early does not progress. Treatment and support brain damage, which may cause and only the actions controlled develop normally and do not have are tailored to meet individual needs. a wide range of symptoms. by that area will be affected. learning difficulties.

235 CHROMOSOMAL AND GENETIC DISORDERS The way in which the body develops, grows, and functions is rare and affecting one or more body systems. These disorders determined by the 20,000–25,000 pairs of genes arranged in 23 may develop as a result of an incorrect number of one of the pairs of chromosomes in the body cells. Gene and chromosomal chromosomes—as occurs, for example, in Down syndrome abnormalities may sometimes cause no noticeable problems, but and Turner syndrome—or as a result of a defect in one of the they can also produce a wide range of disorders, each one being genes, as is the case with cystic ﬁbrosis.

Neuroﬁbromatosis AFFECTED UNAFFECTED Normal NEUROFIBROMATOSIS gene PARENT PARENT gene THIS IS A GENETIC DISORDER IN WHICH NON- CANCEROUS GROWTHS (NEUROFIBROMAS) DEVELOP ON NERVE FIBERS THROUGHOUT THE BODY.

Symptoms usually develop in childhood and include PROBLEMS IN NEWBORNS I PROBLEMS DISORDERS flat, brown patches and freckles on the skin, and soft swellings under the skin, which may be small or large and disfiguring. Further problems may develop if the swellings press on nearby tissues. There may also be learning difficulties, and some children develop epilepsy. AFFECTED CHILDREN UNAFFECTED CHILDREN Rarely, the neurofibromas become cancerous. A rarer form of the condition affects adults. In this form, tumors AUTOSOMAL DOMINANT do not develop under the skin but the inner ear is often INHERITANCE PATTERN SPINAL NEUROFIBROMAS affected, which can cause hearing problems. In both Neurofibromatosis is inherited This color-enhanced MRI cases, CT or MRI scanning may be arranged to look in an autosomal dominant way. scan shows the presence If both a neurofibromatosis of two large neurofibromas for tumors. There is no cure, but large tumors may be and a normal gene are present, (colored green) in the spinal removed if they cause problems. Educational support the neurofibromatosis gene cord (colored purple) of the may be needed for children with learning difficulties. will override the normal one. chest and lower back.

EFFECTS OF CYSTIC FIBROSIS PHENYLKETONURIA CYSTIC FIBROSIS CF can affect various parts of the IN THIS GENETIC DISORDER THERE IS LACK OF AN ENZYME THIS GENETIC DISORDER AFFECTS MUCUS-PRODUCING body, but the main areas involved THAT BREAKS DOWN PHENYLALANINE IN PROTEIN, WHICH GLANDS AROUND THE BODY, CAUSING THEM TO are the lungs and pancreas, which MAY LEAD TO BRAIN DAMAGE. PRODUCE ABNORMALLY THICK MUCUS. produces digestive enzymes.

Phenylketonuria (PKU) is a rare autosomal recessive Cystic fibrosis (CF) is one of the more common genetic Sinuses disorder in which the body does not produce an disorders: about 1 in 2,500 babies is born with the These cavities in the skull become inflamed (sinusitis). enzyme that breaks down phenylalanine, a substance in condition and 1 in 25 people carry the CF gene. It is protein-containing foods. Instead, it is broken down into inherited in an autosomal recessive manner, so a child Lungs harmful chemicals. Symptoms usually develop between must inherit two copies of the CF gene to be affected. Mucus buildup in the lungs six and 12 months and may include developmental The disorder affects all the mucus-secreting glands but leads to coughing, breathing delay, vomiting, and seizures. If PKU is not treated, brain the lungs and pancreas are particularly affected; the difficulty, and infections. damage can result, causing learning difficulties. Treatment latter often produces insufficient digestive enzymes due Pancreas is with special milk containing enough protein but little to obstruction by the thick mucus. A newborn baby Digestion is inefficient because the pancreas fails to phenylalanine, and later a diet low in phenylalanine. with CF may have a distended abdomen and fail to produce sufficient enzymes. With early treatment, children develop normally. All pass feces for a few days. Later, the infant may grow babies are screened for PKU shortly after birth. slowly, fail to put on weight, suffer from recurrent chest Intestines Problems with the infections, and produce pale, greasy feces. Permanent absorption of nutrients occur. Normal PKU CARRIER CARRIER lung damage, liver damage, and diabetes mellitus may gene MOTHER FATHER gene also develop. High levels of salt are found in the sweat, and this may be used to make the diagnosis. Regular physical therapy is needed to clear mucus in the airways, and antibiotics are given for chest infections. Other MUCUS-FILLED treatments include a LUNGS This colored chest high-calorie diet, X-ray of a person vitamins, and enzymes with CF shows to aid digestion. A NORMAL CARRIER CARRIER AFFECTED that some of the CHILD CHILD CHILD CHILD heart–lung transplant airways are filled may be possible in with mucus (green), AUTOSOMAL RECESSIVE INHERITANCE PATTERN which will cause A child must inherit the PKU gene from both parents to some cases. All babies breathing difficulty develop the condition. If one PKU and one normal gene are are tested for CF as well as a inherited, the child will not have PKU but will be a carrier. shortly after birth. persistent cough.

236 PROBLEMS IN NEWBORNS

TRISOMY 21 DOWN SYNDROME This picture of NEONATAL SCREENING THIS GROUP OF PHYSICAL AND MENTAL PROBLEMS IS an individual’s CAUSED BY THE PRESENCE OF AN EXTRA COPY OF ONE 1 23 4 5 chromosomes PHYSICAL EXAMINATION OF THE CHROMOSOMES (CHROMOSOME 21). shows that there Babies are checked for a number of conditions are three copies soon after birth and again at six weeks. Their of chromosome Down syndrome is the most common chromosomal 6 7 8 9 10 11 12 appearance is checked for signs of various abnormality, and maternal age is a major risk factor for 21 (trisomy 21), problems, and hearing tests are also offered. revealing that the having an affected baby. The features and severity of 151413 181716 person has Down The checks include: the condition vary from one individual to another but syndrome. typically include short stature, characteristic facial 19 20 21 22 X X CONDITION WHAT IS DONE features, and learning difficulties. Children with Down An extra copy of I DISORDERS syndrome are at increased risk of congenital heart chromosome 21 Physical The physical appearance is defects, respiratory problems, leukemia, vision and abnormalities checked carefully for signs of hearing problems, and an underactive thyroid gland. Round face Epicanthal skin folds conditions such as spina bifida They are also at increased risk of developing dementia and broad (skin folds from eyelid and cleft palate. The reflexes may also be checked. from the age of 40. During pregnancy, tests are offered head to nose) to give an indication of the risk of having an affected Flat nasal bridge Protruding tongue Congenital The hip joints are manipulated child and, if necessary, amniocentesis or chorionic villus (due to reduced dysplasia of to check that the top of the femur sampling will be offered to make a definitive diagnosis. Small chin muscle tone) the hips (thighbone) is positioned securely If the condition is not detected before birth, it can be in the socket of the pelvis. Short neck confirmed later by chromosome analysis. A child with Down syndrome may Abnormal A boy’s testes are examined need long-term specialized positioning to check that they sit within care and treatment; parents of the testes the scrotum. may also need support.

Congenital A light is shone into the eyes BABY WITH DOWN Excessive cataracts to check whether there are This baby has the round joint laxity any opacities in the lens. face, almond-shaped eyes, ﬂat-bridged nose, small chin, and protruding tongue that Single crease on palm are typical of children with Congenital heart The heart is checked for various Down syndrome. disease structural abnormalities by listening for heart murmurs 1:28 with a stethoscope. Poor muscle tone 1:500 BLOOD TESTS 1:1,000 A heel-prick blood sample is taken from babies FEATURES within a week of birth to test for certain genetic OF DOWN 1:1,500 disorders. The blood sample is sent to a laboratory

RISK OF DOWN SYNDROME RISK OF DOWN 20 25 30 35 40 45 SYNDROME for analysis. The tests vary by state, but all test for MATERNAL AGE (YEARS) Wide space A number of physical between big features are typical phenylketonuria and congenital hypothyroidism. RISK OF HAVING A BABY WITH DOWN SYNDROME toe and of Down syndrome, Maternal age is the most important risk factor for having a second toe although they may baby with Down syndrome. The risk increases with a woman’s not all be present in CONDITION WHAT IS DONE age, reaching about 1:900 by age 30 and 1:28 by age 45. one individual. Phenylketonuria The level of phenylalanine (PKU) is checked. In PKU, harmful breakdown products of TURNER SYNDROME phenylalanine build up and A RARE CHROMOSOMAL DISORDER, THIS OCCURS can cause brain damage. WHEN A GIRL HAS ONLY ONE COPY OF THE FEMALE Congenital Levels of thyroid hormones X CHROMOSOME INSTEAD OF THE USUAL TWO. 1 23 4 5 hypothyroidism are checked. A lack of thyroid hormones can lead to feeding At birth, features of Turner syndrome may include puffy problems, poor growth, and feet, a broad chest, low-set ears, a short, wide neck, and developmental delay. feeding difficulties. However, there may be no signs until 6 7 8 9 10 11 12 later in childhood, when short stature becomes apparent Cystic fibrosis The level of trypsinogen (an or when there is delay in the onset of puberty. Other (CF) enzyme produced by the pancreas) is measured. CF causes recurrent problems may include abnormal narrowing of the aorta, 151413 181716 chest infections, slow growth, kidney abnormalities, hearing problems, and, later, and digestive problems. infertility. Chromosome analysis is used to confirm the diagnosis. Estrogen and growth-hormone supplements 19 20 21 22 X Sickle cell disease Levels of abnormal hemoglobin may be given to stimulate growth and help bring on are checked. Sickle cell disease ONLY ONE X CHROMOSOME Missing X affects the red blood cells and normal puberty; estrogen is continued for life. Other This set of chromosomes from a chromosome can be associated with anemia disorders are treated as appropriate—for example, surgery woman with Turner syndrome and delayed growth. to treat narrowing of the aorta. shows an X chromosome is missing.

237 ANATOMICAL PROBLEMS Problems can occur at any stage in the development of a fetus are internal—heart defects, for example—and may take time to and may affect the structure of one or several areas of the body. show themselves through symptoms developing or signs being Some anatomical problems are immediately obvious at birth detected during routine newborn examinations. It is usually because they are clearly visible, such as a cleft lip. Other problems possible to treat most anatomical problems.

Ductus arteriosus HEART DEFECTS Open in fetus NEURAL TUBE DEFECTS A NUMBER OF STRUCTURAL HEART ABNORMALITIES MAY DEFECTS OF THE SPINAL CORD (SPINA BIFIDA) AND BRAIN BE PRESENT AT BIRTH; SOME MAY RESOLVE ON THEIR ARISE DUE TO ABNORMAL DEVELOPMENT OF THE NEURAL OWN, BUT SOME REQUIRE SURGICAL CORRECTION. TUBE DURING EARLY PREGNANCY. Foramen ovale Heart defects may be due to persistence of the special Open in fetal heart If the neural tube (see p.99) fails to close properly, brain features of the fetal heart that normally disappear at and spinal cord defects may be present at birth, ranging birth, such as an open foramen ovale and patent (open) from a minor abnormality signiﬁed only by a dimple or PROBLEMS IN NEWBORNS I PROBLEMS DISORDERS ductus arteriosus. Alternatively, they may result from tuft of hair on the lower back, to part of the spinal cord FEATURES OF failure of the fetal heart to develop normally during THE FETAL HEART being exposed; rarely, the brain is affected. In severe pregnancy, as with coarctation of the aorta (narrowing The placenta supplies cases, leg movement and sensation may be affected of the body’s main artery close to the heart) and valve oxygen to the fetus, as well as bowel and bladder control. A fetal anomaly defects. Sometimes, several problems are present. Heart and so most blood scan (see p.139) and blood tests may detect the condition bypasses the fetal defects may cause shortness of breath, which may in pregnancy. Taking folic acid supplements before and lungs by way of the affect feeding and thereby impair growth. They may foramen ovale and during pregnancy reduces the risk of neural tube defects. be detected as murmurs during a routine examination, ductus arteriosus. or may be found when investigating symptoms. If a Ribcage defect is suspected, the heart can be examined using KEY OXYGEN-RICH BLOOD echocardiography (ultrasound scanning of the heart). OXYGEN-POOR BLOOD Spinal cord bulges out Many defects clear up without treatment, but about MIXED BLOOD of fetus’s back a third need corrective surgery. Ductus arteriosus Is still open; it SPINA BIFIDA IN A FETUS Mixing of blood Ductus should have closed This 3-D ultrasound scan shows Oxygen-rich arteriosus a bulge in the lower back where Has closed blood mixes with Aorta oxygen-poor blood the spinal cord bulges through a gap in the spinal column.

HERNIA HERE PART OF AN ORGAN, MOST COMMONLY THE GUT, PROTRUDES THROUGH A WEAKENED AREA OF MUSCLE, SOMETIMES CAUSING A VISIBLE BULGE.

A hernia may occur at various sites, but an inguinal hernia is particularly common in babies, especially boys. It typically causes an intermittent swelling in the groin or scrotum that appears when a baby cries. A hernia may become trapped (strangulated), in which case it appears as a persistent lump and is accompanied Foramen Foramen ovale ovale Is still open; it by vomiting and being unwell. A strangulated hernia is Has closed should have closed Left a serious condition that requires emergency treatment. ventricle To avoid this, early surgery is generally recommended HEALTHY NEWBORN HEART HEART WITH OPEN FORAMEN OVALE HEART WITH OPEN for an inguinal hernia. With the first breath, the newborn lungs If the foramen ovale fails to close, DUCTUS ARTERIOSUS are inflated, triggering changes in the oxygen-rich blood is able to travel If this small duct persists in the heart that allow it to work independently to the right side of the heart, where newborn, oxygen-poor blood passes of the placenta. The foramen ovale and it recirculates to the lungs. This results into the aorta, where it joins oxygen- the ductus arteriosus both close. in a less efficient circulation. rich blood from the left ventricle.

PYLORIC STENOSIS may be very forceful (projectile vomiting) and cause hunger immediately afterward. Admission to the hospital IN THIS CONDITION, THE OUTLET OF THE STOMACH for intravenous fluids may be necessary because affected IS NARROWED, WHICH PREVENTS FOOD FROM PASSING FROM THE STOMACH INTO THE SMALL INTESTINE. babies tend to become dehydrated. The doctor will examine a baby’s abdomen, sometimes during a feeding, Pyloric stenosis is about five times more common in and an ultrasound scan or special X-rays may be taken INGUINAL HERNIA ON EACH SIDE boys than in girls, but its cause is not known. Symptoms to confirm the diagnosis. The condition is treated by a This six-month-old boy has a bilateral inguinal hernia tend to develop between three and eight weeks after surgical procedure to widen the stomach outlet, which (a hernia on each side of the groin) that is so large it has birth. The main symptom is persistent vomiting, which usually cures the problem completely. extended down into the scrotum and obscured the genitals.

238 PROBLEMS IN NEWBORNS I DISORDERS CONGENITAL DYSPLASIA OF THE HIP PRESENT AT BIRTH, THIS PROBLEM OCCURS WHEN THE UPPER END OF THE FEMUR (THE “BALL” OF THE THIGHBONE) DOES NOT FIT PROPERLY INTO THE SOCKET OF THE PELVIS. IF UNTREATED, CONGENITAL HIP DYSPLASIA MAY CAUSE PROBLEMS WHEN WALKING STARTS.

Congenital hip dyplasia ranges from assessment. The condition may be treated mild instability of the hip joint, through by placing the baby in a splinting device subluxation (in which the ball slips out for several months to hold the ball of the of the socket but can be maneuvered femur in the socket of the pelvis. Progress back into position), to full dislocation is monitored with X-rays or ultrasound (in which the ball of the femur lies scans. If this treatment is unsuccessful, completely outside the socket in the surgery to correct the hip dysplasia may pelvis). The mildest forms may result be recommended. from loose ligaments that allow the ball to move excessively. The more severe Pelvis Provides the “socket” forms are due to failure of the hip socket part of the hip’s to develop normally. Early detection of ball-and-socket joint the condition can prevent other problems LOOKING FOR SIGNS from developing and reduce the Head of femur Shallow socket OF HIP PROBLEMS At newborn checks, a doctor likelihood of surgical treatment being Provides the “ball” that Femur does not fits into the socket bends a baby’s knees and needed. Consequently, the condition is fit properly in abnormal hip socket manipulates the legs to see checked for during neonatal screening NORMAL HIP if the hip joints are stable (see p.237), and in some cases ultrasound The ball-shaped end or if the ball can be moved scanning may also be carried out. Left of the upper femur fits in and out of the socket. untreated, congenital hip dysplasia snugly into the cup- may lead to restricted leg movement, shaped socket of the HIP WITH POTENTIAL PROBLEMS pelvis. This arrangement If the socket fails to develop properly in pregnancy, shortening of the affected leg, or a allows a wider range of it does not form the cup needed to hold the ball limp. If the condition is suspected, an movement than any securely. The surrounding tissues cannot hold the orthopedic specialist will make an other joint in the body. ball in the socket, and problems can develop.

CLEFT LIP AND PALATE DIGIT ABNORMALITIES FAILURE OF THE UPPER LIP AND ROOF OF THE MOUTH IN POLYDACTYLY, THERE ARE MORE THAN THE NORMAL TO CLOSE PROPERLY DURING DEVELOPMENT, THIS NUMBER OF DIGITS. IN SYNDACTYLY, TWO OR MORE DIGITS CONDITION SOMETIMES RUNS IN FAMILIES. ARE FUSED TOGETHER, GIVING A WEBBED APPEARANCE.

A cleft lip and palate are among the most common Polydactyly may occur by itself, or occasionally it congenital defects. They may occur singly or together, may be a feature of a genetic disorder. It may affect and one or both sides may be affected. Risk factors the fingers or toes or both. The additional digits are for the condition include taking certain drugs (in often poorly developed, but sometimes they are fully particular, some anticonvulsants) during pregancy and formed and functional. Poorly developed digits are drinking excessive amounts of alcohol when pregnant. usually removed surgically. Cleft lip and palate may cause problems with feeding, Syndactyly, in which the normal webbing at the and speech may be affected if treatment is delayed. A base of the digits extends farther along the digits, buildup of fluid in the middle ear may also occur. The may likewise affect the hands and the feet. When it usual treatment is surgery. Surgical repair of the cleft affects the feet, it tends to occur between the second lip is usually performed first, with the cleft palate BEFORE CORRECTIVE and third toes. Often, no treatment is necessary, but repair being performed later. A plate may be fitted to SURGERY sometimes surgery is recommended to release the In this baby of about three cover the gap in the palate and help with feeding until months, the cleft lip extends fingers if the webbing restricts movement. surgery. Corrective surgery often achieves good results up to affect the nostril and and makes it possible for speech to develop normally. septum (division) of the nose. TWO WEEKS AFTER SURGERY

TRIMMING NOSTRIL REPAIR CLOSING THE LIP COMPLETION 1 The edges of the cleft, 2 The bottom of the nose 3 The edges in the lip area 4 The stitches now close AN EXTRA FINGER which here extend up from is stitched to form a complete are brought together carefully the openings entirely, and the A sixth ﬁnger can clearly be seen on this baby’s hand. the lip and into the nose, are nostril as similar as possible with multiple stitches to form procedure is complete. Healing This condition, known as polydactyly, can be passed carefully trimmed. to the one on the other side. the upper lip. will take several weeks. down in families or may occur with no family history.

239 PROBLEMS AFFECTING THE MOTHER AFTER DELIVERY

FOR MOST WOMEN, CHILDBIRTH PROGRESSES WITHOUT ANY MAJOR ISSUES. MOST POST-DELIVERY PROBLEMS CAN BE RESOLVED AND ARE NOT SERIOUS. BUT EVEN IN THESE WOMEN, PROBLEMS MAY DEVELOP AFTER THE BIRTH. HOWEVER, SOME PROBLEMS, SUCH AS DEEP VEIN THROMBOSIS, REQUIRE EVENTS THAT OCCUR DURING DELIVERY OR OTHER FACTORS, SUCH AS A URGENT TREATMENT BECAUSE THEY CAN BE LIFE-THREATENING. OTHERS, PREEXISTING CONDITION, MAY INCREASE THE LIKELIHOOD OF PROBLEMS. SUCH AS INCONTINENCE, THOUGH NOT SERIOUS, CAN BE DIFFICULT TO TREAT.

POSTPARTUM HEMORRHAGE shock. If a primary PPH occurs, careful examination is needed; blood loss and THIS IS DEFINED AS THE LOSS OF MORE THAN 18 FL OZ (500 ML) OF BLOOD blood pressure are closely monitored. WITHIN ONE DAY OR SIX WEEKS OF DELIVERY. SUCH BLEEDING CAN BE LIFE-THREATENING AND NEEDS URGENT TREATMENT. A blood transfusion and drugs to help the uterus contract may be given. Surgery Postpartum hemorrhage (PPH) can be causes of primary PPH are uterine atony may be needed. Two common causes primary (within 24 hours of delivery) or (the uterus can no longer contract) and of secondary PPH are infections of the secondary (between 24 hours and six retained placental tissue. Very heavy uterine lining and retained tissue. Any weeks after delivery). The most common bleeding may lead to life-threatening causes are investigated and treated.

Placenta Does not detach from uterine wall as usual

Wall of uterus

RETAINED PLACENTA PROBLEMS AFFECTING THE MOTHER AFTER DELIVERY AFFECTING THE MOTHER I PROBLEMS DISORDERS Tissue left behind in the uterus is a cause of UTERINE MUSCLE primary and secondary This micrograph shows muscle from PPH. All the tissue EMERGENCY CESAREAN SECTION the uterine wall. Atony of this muscle needs to be removed This surgical procedure to deliver a baby is (where it cannot contract properly) is to stop the bleeding associated with an increased risk of both a cause of bleeding after delivery. from the uterine lining. primary and secondary PPH.

including frequent urination. There is often a feeling of PROLAPSE OF THE UTERUS RISK FACTORS FOR UTERINE something in the vagina, and in severe cases a lump AND VAGINA PROLAPSE AND VAGINA may be felt beneath the vagina. Stress incontinence, in IF THE MUSCLES AND LIGAMENTS THAT SUPPORT THE which there is urine leakage when abdominal pressure RISK FACTORS UTERUS AND VAGINA ARE WEAKENED, A PROLAPSE MAY is increased, for example when laughing, is often OCCUR WHERE THEY BECOME DISPLACED. associated with a cystocele (a prolapse affecting the Increasing age (the risk doubles with each decade of life) The tissues supporting the uterus and vagina can be bladder) and is a common symptom after childbirth. weakened by childbirth combined with other risk factors Kegel exercises may be helpful in mild cases. After Having a vaginal delivery (see table, right). The degree of uterine prolapse varies menopause, estrogen supplements may be used to from slight displacement to the uterus protruding from help strengthen the supporting tissues. A vaginal ring Having several vaginal deliveries (the number increases the risk) the vagina. Symptoms of uterine and vaginal prolapse pessary may be inserted to keep the uterus in position. can include problems with defecation or urination, In older women, corrective surgery may be considered. Being overweight or obese

Having a family history of prolapse Uterus prolapsed into the vagina Bladder Carrying a large fetus during pregnancy Can bulge into front wall of vagina Rectum Pushing for a long time (prolonged second stage of labor) Can bulge into back wall Having an episiotomy of vagina Having an assisted delivery, for example by forceps TYPES OF PROLAPSE Vagina A uterine prolapse may be Bulges from bladder or Receiving the drug oxytocin during labor associated with a vaginal rectum can be seen here prolapse involving the rectum on examination (rectocele) or the bladder Having reduced levels of estrogen after menopause (cystocele). Any of these types of prolapse can occur Suffering from a chronic cough or chronic constipation together or alone.

240 PROBLEMS AFFECTING THE MOTHER DELIVERY AFTER

Toned muscles of Lax muscles of pelvic floor pelvic floor URINARY Uterus FECAL Support bladder, Do not support INCONTINENCE Rectum Bladder uterus, and rectum any organs INCONTINENCE LEAKS OF URINE DUE TO RAISED PRESSURE CONTROLLING THE PASSAGE OF FECES IN THE ABDOMEN WHEN COUGHING OR OR GAS MAY BE MORE DIFFICULT THAN LAUGHING ARE COMMON AFTER CHILDBIRTH. NORMAL AFTER CHILDBIRTH. Problems with urine leakage during Fecal incontinence may result from pregnancy make stress incontinence after weakness in the pelvic floor muscles, childbirth more likely. The muscles of the which may also cause a prolapse of pelvic floor are put under pressure during the rectum, or an injury to the ring of pregnancy and childbirth (and hormonal muscle around the anus, perhaps as a changes during pregnancy make the result of a tear (see p.233). Tears are muscles looser). A prolapse affecting the more likely if the baby delivered is big, bladder (called a cystocele, see opposite) the pushing (second) stage of labor is is a particular cause of urine leakage. prolonged, or the baby is born facing CONTRACTED PELVIC RELAXED PELVIC Stress incontinence may be temporary, FLOOR MUSCLES FLOOR MUSCLES upward. Fecal incontinence may last for several weeks, or persist for longer persist for a few months or may clear periods. Kegel exercises can help, but for PELVIC FLOOR MUSCLES AND INCONTINENCE up very quickly. For a few women, it Looseness of the pelvic floor muscles, which support the a few women surgery may be offered uterus and bladder, predisposes a woman to incontinence. persists in the longterm. Kegel exercises to tighten the bladder supports and to Kegel exercises performed regularly during pregnancy and can help, but surgery may be offered if correct a prolapse, if necessary. after childbirth can help prevent or lessen this. there is a persistent problem.

I DISORDERS WOUND INFECTION INFECTION OF STREPTOCOCCUS A This SEM image shows a THE WOUND FOLLOWING A CESAREAN SECTION, THE UTERUS chain of streptococcus A AN EPISIOTOMY, OR A TEAR MAY BECOME INFECTED ALSO KNOWN AS ENDOMETRITIS, AN INFECTION bacteria. This bacteria AND REQUIRE TREATMENT WITH ANTIBIOTICS. OF THE UTERINE LINING AFTER DELIVERY IS NOT can cause inﬂammation UNCOMMON AND CAN BE PAINFUL. in the endometrium. It is The area around any such wound from childbirth also a possible cause of will be reddened and may feel warm if infected; If labor is prolonged or there is a long time between wound infections. Such there may also be tenderness or pain. If discharge membrane rupture and delivery, the likelihood of infections are usually treated with antibiotics. is present, a swab will be taken and sent off for endometritis is increased. Women who have a laboratory analysis for the presence of bacteria. Once cesarean section are at increased risk, particularly the swab has been taken, antibiotics may be given if the procedure is performed after the membranes based on those bacteria that are likely to be present. have ruptured or if labor has already started. passed vaginally after delivery (the lochia) will have The prescription may then be amended once the Endometritis causes pain in the lower abdomen. an unpleasant odor. Swabs of the lochia will be swab results are back. The antibiotics should clear Body temperature may be raised, causing a fever taken and tested to look for infections. Antibiotics the infection so that healing can take place. and chills. In addition, the ﬂuid that is normally should clear the condition.

Blood clot DEEP VEIN Clot has become lodged here, THROMBOSIS and blood cannot flow past it Vein WHEN A CLOT FORMS IN ONE OF THE DEEP in leg VEINS OF THE LEG, FRAGMENTS OF THE CLOT CAN BREAK OFF AND TRAVEL TO THE LUNGS. Women are at increased risk of deep vein thrombosis (DVT) after childbirth because there is an increased tendency for the blood to clot. Women who have a cesarean section are also at higher risk and may be given special hose to wear for a day or two after surgery. An affected leg may feel painful and warm; it may also be swollen and reddened. A PULMONARY EMBOLISM Body temperature may rise slightly. Clots that This scintigram shows blood flow in travel and cause a blockage in the lungs lead the lungs. A blood clot has traveled around the body and become lodged to a condition called pulmonary embolism in the small vessels in the lung, (PE), which is life-threatening and may cause causing an embolism and preventing persistent shortness of breath and chest pain. Fibula the lung (seen on the left) from If DVT is suspected, urgent tests will be receiving its normal amount of blood. Tibia arranged, such as Doppler scanning to check VENOGRAM OF THE LOWER LEG Bone of Dye is injected into blood vessels and its passage Deep veins blood flow in the legs’ deep veins. Drugs will lower leg through these recorded on special X-rays to be given to reduce the tendency of the blood detect DVT. A blood clot is shown on this to clot and so reduce the risk of a PE. venogram in one of the deep veins of the leg. THE CIRCULATORY SYSTEM

241 DEPRESSION AFTER PREGNANCY NOT BONDING THE HORMONAL AND LIFE CHANGES THAT FOLLOW THE DELIVERY OF A BABY CAN BE WITH A BABY ASSOCIATED WITH LOW MOOD AND TEARFULNESS. POSTPARTUM SUPPORT, FROM FAMILY New mothers with AND MEDICAL PROFESSIONALS, IS VITAL TO HELP WOMEN THROUGH THIS EMOTIONAL TIME. depression may have little interest in their babies and The mood changes that often follow childbirth vary: depression tends to recur, and a family history of the feel they are not forming a from mild and transient in most cases to severe and condition puts women at increased risk. Other factors, close bond. This can worsen debilitating in a few. Any symptoms of low mood, including lack of sleep, relationship problems, and the feelings of sadness and guilt they already have. whether they are mild or severe, should be noted a difficult labor, can play a role. Depression can so that the appropriate help can be given. develop within the first six months after delivery with various symptoms including Baby blues feelings of exhaustion, having little interest in Known as the baby blues, feelings of sadness often the baby, guilt, loss of appetite, signs of anxiety, accompanied by weeping are very common and begin and problems sleeping. Antidepressant drugs within a few days of the birth. There can be marked may be recommended, and an improvement in mood swings with feelings of sadness one minute symptoms should be seen within a few weeks. followed by elation the next. New mothers may also be irritable and tired, partly due to hormonal Puerperal psychosis fluctuations but also due to an inevitable lack of sleep. A personal or family history of mental illness The baby blues usually settle within a few weeks. increases the risk of this condition developing. Symptoms appear within about three weeks of Postpartum depression childbirth and include hallucinations, problems This condition is thought to relate to the hormonal sleeping, and periods of mania alternating with changes that also cause the baby blues—the fall in depression. This serious illness requires prompt progesterone and estrogen after delivery. Postpartum and specialist help and hospital treatment.

Postpartum depression Puerperal psychosis Serious mental health Rare but serious condition; COPING STRATEGIES condition that affects 1 in 10 1 in 1,000 women affected women after having a baby after having a baby A few simple measures can help new mothers who time with those who offer emotional support as PROBLEMS AFFECTING THE MOTHER AFTER DELIVERY AFFECTING THE MOTHER I PROBLEMS DISORDERS may be feeling low after the birth of a baby. Feelings well as practical help. Reassurance from midwives of isolation are common, so it is vital to spend and physicians is helpful too.

Baby blues Experienced New mothers should be encouraged to accept the Seeing the outside world, when they feel able, by most new help and support of others, whether it is by spending and talking to other people helps achieve a positive mothers to time talking or allowing them to help with the baby. outlook, making having a new baby more enjoyable. some degree

Finding “me” time can make a big difference, as can It is important to resist being self-critical and to be seizing opportunities to sleep, following the age-old proud of achievements, no matter how small. This is rule of sleeping whenever the baby sleeps. a steep learning curve, especially with the ﬁrst baby.

HOW COMMON IS DEPRESSION? Friends and family can be a great source of support New mothers need to avoid having unreasonable Baby blues are very common, affecting most new and encouragement. New mothers should try to expectations, for example, by learning to accept that it mothers. Postpartum depression is less common; and maintain regular contact and avoid isolation. does not matter if household chores are left undone. puerperal psychosis affects a small number of women.

BREAST CRACKED NIPPLES BLOCKED MILK DUCT ENGORGEMENT THE SKIN OF THE NIPPLES MAY A DUCT THAT DRAINS MILK FROM THE BREAST MAY BECOME Milk- BECOME CRACKED, PARTICULARLY IN BLOCKED, CAUSING AN AREA OF BREAST TISSUE TO BECOME BEFORE FEEDING IS ESTABLISHED, MILK producing THE EARLY DAYS OF BREASTFEEDING. PAINFUL AND SWOLLEN. THIS PROBLEM IS RELATIVELY COMMON. lobule CAN ACCUMULATE IN THE BREASTS, CAUSING PAIN AND SWELLING. Failing to latch on properly is the Milk may accumulate in the affected Surrounding Engorgement can also occur if a main cause of this painful condition, area, causing it to be tender and painful. tissue presses on and woman has to stop breastfeeding. The which is worse as the baby latches In some cases, the duct or the swollen blocks duct condition predisposes to infection in on or comes off the nipple. It is area becomes infected, causing mastitis the breast (mastitis, see opposite). It important to ensure that the baby (see opposite). A blocked duct usually is essential to wear a supportive bra. is positioned correctly (see p.207). clears up within a day or two. Making Acetaminophen may help ease any Emollient creams may provide relief, sure that the baby latches on properly pain. The problem should settle within but need to be washed off before will help relieve the problem. It is a few days once a baby is latching on feedings. The problem should essential to continue breastfeeding even and feeding well. When breastfeeding is slowly resolve as feeding techniques when this is painful. being stopped, the number of feedings improve. If the breasts continue to OBSTRUCTED FLOW should be reduced over a week or be painful, medical help should be If the ﬂow of milk out of the breast is two; in this way, the breasts become sought because an infection requiring blocked in a particular milk duct, the milk acclimatized to producing less milk. antibiotics may have developed. will accumulate in that area of the breast.

242 PROBLEMS AFFECTING THE MOTHER DELIVERY AFTER MASTITIS THIS IS A COMMON PROBLEM IN THE FIRST SIX WEEKS OF BREASTFEEDING, IN WHICH AN AREA OF BREAST TISSUE BECOMES INFLAMED AND TENDER. ONE BREAST, OR LESS COMMONLY BOTH, MAY BE AFFECTED.

This common condition, which affects improvement should be seen within two around 1 in 10 women who breastfeed, or three days of taking them. Without results from an infection in the breast treatment, an abscess (a collection of pus) tissue. A common cause is the bacterium may form, in which case a firm and Staphylococcus aureus. The affected area will painful lump will be felt in the affected be reddened, swollen, and painful. There area; fortunately, such abscesses are may be associated flu-type symptoms, rarely seen today. including a high body temperature and chills. A heated pad on the affected area EXPRESSING MILK LOCALIZED AREA OF REDNESS To prevent the buildup of may promote the flow of milk and An area of the breast affected by mastitis milk, breastfeeding should be provide some pain relief. Antibiotics are becomes increasingly painful, red, and swollen, continued. Any extra milk can usually needed to treat the infection, and extending out from the nipple area. be expressed using a pump.

ALLEVIATING COMMON PROBLEMS

I DISORDERS A number of problems may develop during the early days following childbirth that features of early motherhood. There are many ways to alleviate the various are part of the normal recovery process. At six weeks after delivery, the physician symptoms after childbirth. Talking to the midwife or sharing problems at a postnatal will check that all is well, including that the uterus is shrinking as it should. Mood group can be helpful. If a woman suspects she has problems requiring treatment, changes, including the baby blues (see opposite), are some of the most noticeable such as a urinary tract infection, medical advice should be sought promptly.

VAGINAL SORENESS PROBLEMS WITH URINATION PROBLEMS WITH BOWEL MOVEMENTS Tiny tears and grazes of the vagina or perineum (the Some degree of leakage of urine is common after Constipation is a common problem. Keeping mobile, area between vagina and anus) can cause soreness. pregnancy, particularly when coughing and laughing drinking plenty of ﬂuids, and eating a healthy diet can These areas heal quickly, however, and discomfort (stress incontinence), and may be improved by improve symptoms. If a new mother had an episiotomy should be short-lived. Stitched wounds may cause doing Kegel exercises frequently through the day. If or tear repaired, she may be reluctant to try to have a tenderness for a few weeks. Warm baths provide relief. incontinence persists, medical advice should be sought. bowel movement but these areas will not be affected.

VAGINAL DISCHARGE HEMORRHOIDS SKIN CHANGES After the delivery, there will be bloody discharge from These often develop during pregnancy. They can be Some women have acne in the ﬁrst few weeks after the vagina (called lochia). Initially, this is like having a eased by taking measures to avoid constipation their delivery, while others suffer from dry skin. The period, and then continues in lesser amounts for up to (because straining can make them worse), having warm darkened patches that sometimes develop during six weeks. If it becomes foul-smelling or contains pus, baths, and washing the area carefully after passing a pregnancy should fade gradually; exposure to the medical advice should be sought to rule out infection. motion. Creams and suppositories are also available. sun should be avoided to help this.

CONTRACTIONS SORE BREASTS AND LEAKING MILK WEIGHT LOSS Such “afterpains” may be felt as the uterus starts These problems are common before breastfeeding In the first few days after childbirth, weight loss shrinking. They may be more noticeable when is established. They will be improved by wearing a tends to be rapid due to losing both the weight of breastfeeding due to the release of the hormone supportive nursing bra, feeding the baby on demand, the baby and any retained fluid, passed out in urine. oxytocin, which causes the muscles of the uterus to massaging the breast to help the flow of milk, drinking After this, weight loss will slow; sensible exercise contract. These mild contractions gradually subside. plenty of fluids, and ensuring the baby latches on well. and healthy eating can help shed weight gradually.

POSTNATAL CARE PLAN RESUMING EXERCISE FADING STRETCHMARKS The midwife visits frequently in the ﬁrst few days, Gentle exercise after childbirth has physical and emotional The marks caused by the stretching of the and there is a postnatal check after six weeks. At other beneﬁts. Many types of strenuous exercise should be skin and hormonal changes of pregnancy times, it is important to seek help if any problems arise. avoided until after the six-week postnatal check. never disappear but do fade over time.

243 GLOSSARY

A comprises a hollow ball of cells chorion clitoris allele (the trophoblast) that develops The outermost of the membranes The structure of erectile A particular version of a gene. into protective membranes that surround the developing tissue, part of the female

GLOSSARY Different alleles of the same gene around the embryo, and a group embryo and fetus. Part of it (the genitals, that provides often have different effects. of cells within the trophoblast villous chorion) contributes to pleasurable sensations during called the embryoblast that forming the placenta. sex. Its head is visible as a small amniocentesis will form the embryo itself. See also villi. projection but it also extends A technique used to obtain a See also morula. inward behind the wall of sample of amniotic fluid. A chorionic plate the vagina. It shares the same hollow needle is passed through blastomere The part of the chorion embryonic origin as parts the abdominal and uterine walls, Any of the early cells that result involved in attaching to the of the penis. avoiding the placenta and fetus. from cleavage in the early wall of the uterus. It is part It is performed from the 15th embryo. of the placenta. colostrum week of pregnancy onward. See also cleavage. The milk produced by the breasts chorionic villus sampling immediately after a baby is born. amino acid Braxton Hicks’ contractions (CVS) It is different in appearance and Any of around 20 different kinds The irregular contractions of A technique for obtaining small composition from milk produced of small molecules that are the the uterus that occur during samples from the villi of the subsequently. basic building blocks of proteins. pregnancy. They do not placenta, whose tissue is derived A single protein molecule may indicate that labor is about from the fetus and can be contractions comprise hundreds or thousands to begin. checked for fetal genetic The term used to describe the of amino acids joined together. See also contractions. abnormalities. CVS can regular shortening of the strong be carried out at an earlier muscle of the uterus that amnion breech presentation stage than amniocentesis. marks the beginning of labor. A membrane that grows The term used to describe the See also amniocentesis, villi. Contractions become stronger from the embryonic blastocyst position of the fetus when, rather and more frequent with time. and expands to surround the than its head facing downward, chromosomes They serve first to stretch and developing fetus in the uterus. its buttocks or feet are facing the The structures within a cell’s dilate the cervix, and then to See also blastocyst. cervix when birth is about to nucleus that contain the expel the baby from the uterus. begin. Referred to as a “breech organism’s genes. Humans have See also Braxton Hicks’ amniotic fluid birth,” this is more difficult to 23 pairs of chromosomes in a contractions. The fluid enclosed by the manage than the more common complete set of 46, with a set amnion, which surrounds head-first birth. present in nearly every cell of corpus hemorrhagicum and protects the developing the body. Each chromosome The mature follicle immediately embryo and fetus. C consists of a single long DNA after ovulation, before it cesarean section molecule combined with various develops into a corpus luteum. Apgar score A surgical operation that is proteins. One pair of the 23 are A rating used to assess the health performed in order to remove the sex chromosomes, which corpus luteum (adjective: luteal) of a newborn baby in the first a baby from the uterus by come in two varieties—X A structure in the ovary few minutes after delivery. cutting through the abdominal and Y. Women have two X formed from the remains of a The pulse, reflexes, breathing, and uterine walls. It is often chromosomes, whereas mature follicle after ovulation. movement, and skin color are performed if there are actual or men have one X and one Y. It produces progesterone, rated as 0, 1, or 2, and the expected complications with a which keeps the uterus in scores added together to give normal birth. cilia (singular: cilium) a condition that allows it to the overall Apgar score. The minute, beating hairs on support a potential pregnancy, cervix the cell surfaces of some but if no egg implants, the areola (plural: areolae) The lowest part of the uterus. tissues, such as those lining corpus luteum breaks down The circular area of pigmented It consists mainly of a ring of the fallopian tubes. after a few days as part of skin that surrounds the nipple. connective tissue surrounding a the normal menstrual cycle. narrow, mucus-filled canal that cleavage See also follicle. B connects the rest of the uterus to The early stage divisions of the blastocyst the vagina. During labor, the fertilized egg cell, when it cleaves cotyledon The stage in embryonic canal stretches and widens (divides) into a number of Any of the 15–20 lobes of the development that follows the to allow the baby to pass smaller cells without growing placenta that protrude into the morula stage. The blastocyst through it. in total size. lining of the uterus. 244 GLOSSARY cytotrophoblast a sperm cell to result in a the body is made numb by follicle (adjective: follicular) A group of cells forming the new individual. applying anesthetic to the A small cavity lined with cells. inner cell layer of the trophoblast See also gamete, ovum. outer membrane (dura) of In reproductive contexts, the that plays a role in implantation. the spinal cord, usually in term refers to an ovarian follicle, See also blastocyst, implantation, embryo the lower-back region. It a structure within the ovary syncytiotrophoblast. The earliest stage of allows a mother to remain comprising an oocyte (immature development of a human, conscious during a potentially egg cell) surrounded by a D covering approximately the painful childbirth, or one covering of other specialized decidua first eight weeks after the egg that may involve surgery. cells. Small primordial follicles The endometrial tissues of the is fertilized. (Sometimes the form in the fetal ovary before pregnant uterus, some of which very earliest stages are episiotomy birth, but remain inactive contribute to the placenta. termed the preembryo.) A surgical operation in untill puberty. After puberty, They are shed after birth. See also fetus. which a cut is made into a few follicles every month See also endometrium. the perineum during childbirth start developing into primary embryonic disk to enlarge the opening of the and then secondary follicles, diploid A disk-shaped region of vagina, in cases where the baby’s although usually only one Having two copies of each tissue that appears within the head might otherwise tear the develops fully into a tertiary chromosome. Nearly all body blastocyst after implantation and mother’s tissues. or Graafian follicle, a fluid- cells, except gametes (sex cells), that develops into the embryo. containing structure that releases are diploid. See also blastocyst. estrogen a mature ovum at ovulation. See also haploid. Any of various natural or See also ovum. endoderm synthetic female sex hormones. DNA The lower of the three layers of Natural estrogens are produced follicle stimulating hormone Short for deoxyribonucleic acid, tissue into which the embryonic by follicle cells of the ovary from (FSH) a very long molecule made up disk becomes divided. It later puberty onward. They promote A hormone secreted by the of small individual units. DNA gives rise to the gut and female characteristics such as pituitary gland that affects the is found in the chromosomes associated organs. breast development, and are ovaries and testes. Increasing of living cells, and the order of See also ectoderm, embryonic essential to the menstrual levels of FSH are necessary for the small units “spells out” the disk, mesoderm. cycle and female fertility. puberty to occur in both sexes instructions that determine the and, in women, the hormone characteristics of the organism. endometrium also stimulates follicular See also gene. The inner lining of the uterus. F development during the It grows in thickness during fallopian tube menstrual cycle. E each menstrual cycle, but if Either of the tubes leading to See also follicle. ectoderm no pregnancy occurs it breaks the uterus from the ovaries, The uppermost of the three down and some of its tissues down which an ovum travels folliculogenesis layers of tissue into which the and blood are expelled at after ovulation. The development of a embryonic disk becomes divided. menstruation. The early embryo primordial follicle into It later gives rise to the skin and implants in the endometrium fetus (adjective: fetal) one that is fully mature. nervous system. and later the placenta also The unborn baby in the uterus, See also follicle. See also embryonic disk, develops here. from the time when it begins endoderm, mesoderm. See also implantation, to show a recognizably human fontanelles myometrium, perimetrium. appearance, at approximately The “soft spots” on the ectopic pregnancy eight weeks after fertilization or head of a baby where the A situation in which an early epididymis (plural: epididymides) ten weeks after the start of the underlying skull bones embryo implants outside the The long, highly coiled tube into mother's last menstrual period. have not yet fused together. uterus, usually in a fallopian which sperm pass after leaving See also embryo. tube. Such pregnancies cannot the testis. Sperm become fully forceps (obstetrical) succeed and therefore require capable of fertilization only fimbria (plural: fimbriae) An instrument whose medical intervention. after maturing for several Any of the several fingerlike ends can be eased around days in the epididymis. projections at the end of each a baby’s head during labor egg fallopian tube that help collect if necessary: gentle pulling In humans, the single yolk- epidural an ovum released by the ovary, on the forceps then aids containing cell that can Short for epidural anesthesia, so that it will be conveyed the baby’s exit from the potentially be fertilized by a technique by which part of toward the uterus. birth canal. 245 fundus are haploid, allowing them intervillous space the fetus is positioned with The top part of the uterus, whose to re-create a normal diploid Any of the spaces between the its backbone roughly parallel position can be felt from the individual when they unite villi of the placenta through to the mother’s backbone.

GLOSSARY outside of a woman’s body in the at fertilization. which the mother’s blood later stages of pregnancy. It is See also diploid. circulates. It is here that gases linea nigra the usual site of the placenta. are exchanged between the A pigmented vertical line that human chorionic blood of mother and fetus. often develops on the skin of G gonadotropin (hCG) See also villi. a woman’s abdomen during gamete A hormone produced by the pregnancy. A haploid sex cell, i.e. a sperm placenta that causes the corpus L cell or an unfertilized egg cell. luteum of the ovary to continue labia lobule See also haploid, zygote. producing progesterone, so that Either of the two pairs of folds A small lobe or section of pregnancy continues. that form part of a woman’s an organ, for example, in gene vulva (external genitals), a mammary gland. A length of a DNA molecule hypothalamus comprising the labia majora containing a particular genetic A control center at the base of (the outer labia) and the more lochia instruction. Many genes are the brain, close to the pituitary delicate labia minora (the The fluids expelled from the blueprints for making particular gland. Its many functions include inner labia). uterus via the vagina in the protein molecules, while others stimulating the pituitary gland days after birth. have a role in controlling other to produce luteinizing hormone labor genes. Nearly every cell in the and follicle stimulating hormone. The process of giving birth. In lumen human body contains a complete See also follicle stimulating the first stage of labor, regular The inside space of a tubular set of genes (the genome), hormone, luteinizing hormone. contractions of the uterus stretch structure, such as a blood although different genes are the cervix and widen (dilate) its vessel or glandular duct. “switched on” in different cells. I opening, until it is wide enough implantation for the baby’s head to pass luteal genome The process in which the early through. In the second stage, Relating to the corpus luteum. The complete set of genes embryo (at the blastocyst stage) the baby is born. In the third found in the cell of a human attaches to and becomes stage, the placenta and other luteinizing hormone (LH) or other living species. incorporated within the materials are expelled. A hormone secreted by the endometrium of the uterus. pituitary gland that acts on both germ cell See also blastocyst, lactation ovaries and testes. Increasing A stem cell from which endometrium. A term used to describe the levels of LH are necessary for gametes are derived; also, an process of milk production puberty to occur in both sexes. immature or mature gamete. in vitro fertilization (IVF) by the breasts. LH stimulates testosterone See also stem cell. An assisted-conception production in men and technique that involves removing lanugo plays various roles in the germ layer some of a woman’s unfertilized The fine hair covering the female menstrual cycle. Any of the basic cell layers eggs from her ovaries, fertilizing skin of a fetus. into which the embryonic them with sperm in a laboratory, M disk becomes divided. culturing them until the blastocyst laparoscopy mammary gland See also ectoderm, endoderm, stage, and then introducing them The technique of viewing The milk-producing gland mesoderm. into the uterus so that they can internal abdominal organs of a mammal. In women, implant. The technique may be by inserting an instrument much of the substance of goblet cells used, for example, when a woman (laparoscope) through the the breasts is made up of The mucus-secreting cells found is infertile because her fallopian body wall. The laparoscope mammary-gland tissue. in the surface linings of some tubes have become blocked. is equipped with a miniature tissues, such as those of the See also blastocyst, video camera and illumination, meconium fallopian tubes. implantation. and transmits images to The greenish brown material the outside. expelled by a baby as its first H induction bowel movement. haploid The process of artificially starting lie (fetal) Having only one copy of labor by various means, in The angle of a fetus in the uterus meiosis each chromosome, rather cases where the onset of natural in relation to the mother’s main A specialized type of cell than a pair. Gametes (sex cells) labor is overdue. body axis. Most commonly, division (strictly speaking, 246 GLOSSARY of nuclear division) in menstruation morula N which haploid sex cells are The expulsion of endometrial An early stage in the neonatal created from diploid precursor blood and tissue as part of the transformation of the fertilized Of or relating to a newborn cells. It is more complicated menstrual cycle, its occurrence egg into an embryo. It consists baby (neonate). than normal cell division each month being known as of a solid ball of cells. This stage (mitosis) and takes place a menstrual period. proceeds that of the blastocyst. neural tube in two stages. See also endometrium. See also blastocyst. The hollow tube of cells See also haploid, mitosis. formed in the early embryo mesoderm MRI from which the brain and menarche (pronounced The middle of the three Short for magnetic resonance spinal cord develop. “menarkey”) layers of tissue into which imaging, used to obtain images A girl’s first menstrual period, the embryonic disk becomes of internal organs and structures neuron which indicates that she is divided. The mesoderm later by causing atoms to absorb and A nerve cell. reaching sexual maturity. gives rise to many body tissues, emit radiofrequency waves while including muscle, bone, and the body is held within a strong notochord menopause blood vessels. magnetic field. Compared with A rod of stiff material that The time in a woman’s life when See also ectoderm, embryonic ultrasound scanning, MRI needs develops along the back of menstruation permanently stops disk, endoderm. more time, greater precautions, the early embryo. It largely (usually between 45 and 55 and much more elaborate disappears later but marks years of age). milk duct equipment. It is often used to the position of the future A duct conveying milk from investigate problems indicated vertebral column (backbone). menstrual cycle the milk-producing tissues of by ultrasound scanning and is The monthly changes that the mammary gland to the particularly useful for imaging nuchal translucency take place in a nonpregnant nipple of the breast. Around the central nervous system. screening woman’s reproductive system 15–20 milk ducts open separately See also ultrasound. A technique involving the use during her years of fertility. on the surface of each nipple. of ultrasound scanning to check The cycle (of approximately See also mammary gland. mucus plug the thickness of the fluid layer 28 days) starts on the first day The protective plug of sticky found in a young fetus beneath of menstruation and centers miscarriage material that seals the canal the skin of the back of the neck. upon events in the ovary, where The spontaneous loss of an of the cervix during pregnancy. A thicker than normal layer several egg-containing follicles embryo or fetus from the Its shedding from the vagina may indicate a chromosomal begin to ripen. This is the mother’s body at a time that (known as “the show”) indicates abnormality such as follicular phase of the cycle. is too early for it to survive, that labor is soon to begin. Down syndrome. Usually, just one follicle develops which is usually taken to be fully each month, releasing its any time earlier than 24 weeks mutation nucleus egg from the ovary (a process of pregnancy. Later than this, A change to the genetic makeup The structure within a cell that known as ovulation) halfway the event is termed a premature of a cell, caused, for example, by contains the chromosomes through the cycle, after which or preterm birth. Miscarriage mistakes in copying DNA before See also chromosome. the empty follicle transforms into may be complete, or it may be a cell divides. Mutations in sex a corpus luteum, which marks incomplete (some material is left cells, or in cells of the early O the beginning of the luteal phase in the uterus, a situation that embryo, may cause offspring to oocyte of the cycle. The lining of the requires medical intervention). have unusual genetic features An immature egg cell. uterus (the endometrium) also There are a variety of causes not present in their parents. Oocytes occur within thickens, in preparation for of miscarriage, but the cause follicles in the ovary possible pregnancy. If no may not be obvious. myelin See also follicle. pregnancy occurs in the days An insulating layer along the after ovulation, the corpus mitosis outside of many nerve cells. ovary luteum breaks down; the lack The process by which Its presence allows nerve One of the pair of structures of the hormone it produces chromosomes are split and impulses to travel faster. in a woman’s body in which (progesterone) causes the shared out during normal unfertilized egg cells are endometrium to break down, cell division. The two cells that myometrium matured and from which they too, leading to menstruation, are produced have the same The muscular tissue forming are periodically released. The and the cycle begins again. number of chromosomes the bulk of the uterus. ovaries also produce important See also corpus luteum, as the original cell. See also endometrium, hormones, including estrogen endometrium, follicle. See also meiosis. perimetrium. and progesterone. 247 ovulation nutrients, dissolved gases, and prostaglandins promote uterine septa (singular: septum) The release of an unfertilized waste products. The placenta contractions and are used The membranes separating egg (ovum) from an ovary. also produces hormones. artificially to induce labor. tissues of the body. The decidual

GLOSSARY See also umbilical cord. septa are the divisions between ovum (plural: ova) prostate gland the cotyledons of the placenta An egg cell, especially one placenta previa A gland that surrounds the See also cotyledon. that has been released from A condition in which the urethra in men at the point at an ovary and is ready for placenta forms in the lower which it is joined by the ducts somite fertilization. The term can part of the uterus, sometimes (vasa deferentia) leading from One of several paired structures be applied to the fertilized blocking the entrance to the the testes. Its secretions that form in the mesoderm from egg as well. cervix. It may require delivery contribute to semen. the fifth week of pregnancy See also gamete. by cesarean section. onward. Somites eventually puberty differentiate into the spinal P postnatal The sum total of the bodily events cord and vertebrae, the muscles pelvic floor For the baby, denoting the involved in achieving sexual of the trunk, and the skin. A combination of muscles that period after birth. maturity and adult sexual See also mesoderm. supports the abdominal organs characteristics, occurring over from below. postpartum several years in both boys and girls. sperm For the mother, denoting the A male sex cell, also called a perimetrium period after birth. R sperm cell or spermatozoon. The outer covering of the uterus. relaxin Each cell has a long, mobile tail See also endometrium, preeclampsia A hormone produced by the that allows it to swim toward myometrium. A medical condition that ovary and other tissues, and by and fertilize an egg in the body some women experience the placenta, during pregnancy. of the female. The word is also perinatal during late pregnancy, which is Its functions include softening used in nontechnical contexts Relating to the period around characterized by a combination and relaxing tissues and to refer to semen. birth, including the few weeks of high blood pressure and ligaments in preparation for See also gamete. beforehand and afterward. protein in the urine. It requires childbirth. urgent medical attention (often spermatids perineum including induction of labor) in Rhesus factors The immediate precursors of The area of skin and underlying case it develops into eclampsia, Molecules found on the surfaces sperm cells. When a secondary tissues lying between the external a life-threatening condition. of blood cells in most people spermatocyte completes meiosis, genital organs and the anus. (who are thus termed Rhesus it becomes an early spermatid. The mother’s perineum stretches prenatal positive or Rh-positive) but This small, round cell elongates considerably during childbirth. The term used to describe which are missing from a and changes form to become the period before childbirth. minority (Rhesus negative a late spermatid as part of its pituitary gland or Rh-negative). If a Rhesus- transformation into a mature A complex, pea-sized structure at primitive streak negative mother carries a sperm cell. the base of the brain, sometimes A linear arrangement of cells on Rhesus-positive fetus in a second See also spermatocytes. described as the body’s “master the developing embryonic disk or later pregnancy, her immune gland.” Its direct roles in that indicates the future head- system may attack the fetus. spermatocytes reproduction include the and tail-ends of the embryo. Cells that are at an intermediate secretion of luteinizing hormone S stage in the creation of sperm and follicle stimulating hormone. progesterone semen cells. Spermatocytes undergoing It also produces oxytocin. A hormone produced mainly by The sperm-containing fluid the first stage of meiosis are the corpus luteum of the ovary. released through the penis called primary spermatocytes; placenta Its action causes the lining of when a man ejaculates. Its those that have progressed to A disk-shaped organ formed on the uterus to be in a suitable fluid component derives from the second stage of meiosis are the wall of the pregnant uterus condition to support pregnancy. several glands, including called secondary spermatocytes. by the combined growth of the prostate gland. See also meiosis. tissues from the mother and prostaglandins the early fetus. The fetus’s Hormonelike substances seminiferous tubule spermatogenesis blood circulation flows close produced by many tissues. Any of the coiled tubes in The overall process of sperm by the mother’s in the placenta, They cause altered activity the testis within whose tissues formation, from spermatogonia allowing for the exchange of in neighboring tissues. Some sperm cells are formed. to mature sperm. 248 GLOSSARY 249 blastocyst. , ovum diploid, gamete. (singular: villus/adjective: villous) villus/adjective: (singular: Z pellucida zona The transparent protective around the ovum. It is layer shed by the blastocyst before implantation. See also zygote The diploid fertilized cell formed by the union of two gametes. See also ventouse extractor, Also called a vacuum thata form of suction cap is to an sometimes applied emerging baby’s head during labor: on the ventouse pulling aids the baby’s passage through the birth canal. vernix thatA greasy substance coats of the and protects the skin unborn baby. villi The folded projections that form on the surface of some tissues. The placenta produces villi that are branched structures, comprising stem, secondary, and tertiary villi. The villi contain fetal blood that vessels allow efficient exchange of materials with the mother’s blood supply. Y sac yolk A membrane-bound cavity on the underside of the early thatembryo is the location of first blood-cellthe embryo’s production. (It is not used for storage in humans.) yolk urethra. perimetrium. (plural: vasa vasa (plural: (adjective: uterine) (adjective: deferentia) ultrasonography, an imaging an imaging ultrasonography, high- technique in which frequency sound waves bouncing in the body off tissues can be electronically interpreted images. to yield still or moving A similar called technology Doppler can ultrasonography visualize the speed of moving fluids, such as blood in an artery. convenient Ultrasonography is and lacks so is side-effects, commonly used to check fetal progress and sometimes to aid surgical operations. Either of the two narrow muscular tubes in men that connect the epididymides to the urethra. They store and transport sperm in preparation for ejaculation. See also epididymis, ureter Either of the two tubes that from the kidneys urine convey to the bladder. urethra The tube that urine conveys from the bladder to the outside In men it also of the body. semen during conveys ejaculation. uterus The womb—the hollow muscular organ where the fetus develops during pregnancy. See also endometrium, , myometrium V deferens vas umbilical cord umbilical The flexible cord that attaches fetus to the the developing placenta. blood Fetal circulates to and from the placenta via blood the cord, allowing an in vessels exchange of nutrients and other materials with the mother. See also placenta. blastocyst. U ultrasound The sound frequencies that are too high for the human ear to They form the basis of hear. trophoblast See twins The term used to describe two developed individuals who have in the same uterus at the same time. Nonidentical or fraternal twins occur when two separately fertilized ova implant in the Identical twins uterus together. (which are identical genetically) arise when a single fertilized ovum separates into two parts begins, shortly after cleavage each part going on to become a separate embryo. transition The final part of the first stage strong involving of labor, contractions and the completion of cervical dilation. See also labor. trimester Any of the three periods, of approximately three months each, into which pregnancy is divided. The first trimester is counted as starting from the woman’s final menstrual period before pregnancy. testosterone in The main sex hormone men, which also occurs in in women. lower concentrations In male fetuses, testosterone produced testes promotes by the of male genitals, the development while increased concentrations at puberty induce characteristics such as beard growth and are essential for sperm production. also secrete hormones, hormones, also secrete especially testosterone. . See also testosterone implantation. (singular: (singular:

(plural: testes) (plural:

spermatogonium)

testis testis Either of the two sperm- producing organs in men, located in the scrotum outside Also the main body cavity. called testicles, the testes T syncytiotrophoblast The outer cells of the trophoblast whose contents are linked to form a continuum (a syncytium). They contribute to implantation. See also blastocyst, cytotrophoblast, A substance that lowers the allowing surface tension of water, wetted surfaces to “unstick” from each other more easily. Surfactant in the air sacs of the plays a vital lungs (the alveoli) role in breathing, because it allows the sacs to inﬂate and collapse easily. surfactant stem cell stem A cell capable of dividing and differentiating into more specialized types of cells. The stem cells of the earliest embryo are capable of turning into any of the body’s cell types, while later stem cells, including those rise to a more in adults, can give limited range of specialized cells. spiral artery spiral spiral- One of many small, shaped that arteries supply the uterus. the endometrium of these arteries During pregnancy, grow in size to supply blood from the mother’s circulation to the placenta. See also endometrium. Cells that an early stage represent in the production of sperm cells. in from stem cells They derive rise give the testis and, in turn, to spermatocytes. spermatogonia spermatogonia INDEX

Page numbers in bold indicate extended association neurons 176 blood circulation (mother) practice breathing 134, 169, 172 treatment of a topic attractiveness 62–3 “glow” of pregnancy 130 premature babies 234 awareness, fetal 143, 163, 164 in second trimester 128 respiratory system 26 INDEX A in third trimester 164 breathlessness 146 abscesses B blood groups, Rhesus incompatibility 157, 158, breech birth 189, 196, 203 Bartholin’s 220 baby blues 201, 206, 242 160, 230 bronchi 152–3 mastitis 243 backache blood pressure bronchioles 137, 152, 153 accidents, safety in pregnancy 89 causes of 157, 158, 160, 168 and fingerprints 149 Brown, Louise 11 acne 243 latent phase of labor 188 preeclampsia 229 Brown, Tom 12 adrenal glands 147 bacteria in second trimester 128, 130 brown fat 147 afterbirth see placenta bacterial vaginosis 220 blood tests 11, 160, 237 bulbourethral gland 66 afterpains 243 balanitis 223 blood vessels age of mother 10 bartholonitis 220 in umbilical cord 114, 165, 200 C and Down syndrome 237 Chlamydia trachomatis 225 in uterus 40 cesarean section 203 AIDS 224 epididymo-orchitis 222 body systems 26–7 history 10 air travel 89 gonorrhea 225 bonding, pair 58, 62, 66 and placenta previa 228 alcohol Group B strep transfer 233 bonding with baby 206 twins 197 fetal alcohol syndrome 235 mastitis 243 and bottle feeding 207 wound infection 241 preconception care 10 nongonococcal urethritis (NGU) 225 and depression 242 caffeine, safety 90 safety 90 prostatitis 223 bone marrow, blood cell production 149, cancer, genetic counseling 55 alveoli syphilis 224 159 Candida albicans 220, 223, 225 development of 153, 170 urinary tract infections 231 bones 118–19 capacitation, sperm 67, 80 practice breathing 169 vulvovaginitis 220 development of 106, 184 capillaries 87 surfactant production 152, 165 wound infection 241 hand 126, 135 caps, contraceptive 68 amenorrhea 221 balanitis 223 imaging techniques 17 car travel 89 amino acids 50 bartholonitis 220 limbs 122 cardiotocography 10, 232 amniocentesis 11, 55, 127, 131 “big bang” reproduction 6 newborn baby 210 cardiovascular system 26 amnion 86 bilirubin 151, 235 skeletal system 27 development of 104, 105, 185 amniotic cavity 86 birds, reproduction 7 skull 120–21, 171, 173, 180 see also blood circulation amniotic fluid 103 birth 192–3 bottle feeding 207 carpal tunnel syndrome 231 inhalation of 165, 166 assisted birth 202–3 bowels (fetus) cartilage practice breathing 169 birth positions 196 development of 104, 122 formation of bones 17, 118 problems 228 cesarean section 203 bowels (mother) in larynx 31 water breaking 190 delivery of placenta 200 in first trimester 76 in limbs 122 amniotic sac 95, 103, 127 home births 198 problems after delivery 243 newborn baby 208, 209, 210 multiple births 19, 114 medical advances 11 symptoms of pregnancy 94 synovial joints 119 amphibians, reproduction 7 preparing for 188–9 brachial arches 94 cataracts, congenital 237 ampulla, fallopian tube 36, 84 problems after 240–43 brain cells anal sphincter 137 recovery from 206 anencephaly 139 blastocyst differentiation 87 anatomy shoulder dystocia 233 blood flow in 112–13 cell division 50–51, 75 body systems 26–7 water birth 198–9 cerebral palsy 235 development of embryo and fetus 84–5, 98, breasts 174 birth control 68–9 consciousness 163 184 female reproductive system 34–45 birthing pools 198 control of reproductive system 28, 34 genetic recombination 51 male reproductive system 28–33 bladder (fetus) desire and arousal 64–5 sex cells 58, 59 newborn baby 208–9 development of 123, 132, 167 development of 93, 116–17, 129, 132, 143, 145, stem cells 93, 99 problems in newborn baby 238–9 bladder (mother) 170, 177–9, 180 see also blood cells android pelvis 192 in labor 191 and evolution of pregnancy 8–9 center of gravity 158, 160 anemia 130, 160, 168 prolapse 240 in first two years 212 cephalic presentation 189 anencephaly 139 urinary tract infections 231 hemorrhage 234 cephalopelvic disproportion (CPD) 192, 233 animals blastocoel 77 hydrocephalus 139 cerebellum 129, 132, 176 pregnancy 8 blastocyst newborn baby 208 cerebral cortex 163, 177, 180 reproduction 6–7 cell differentiation 87 in puberty 31 cerebral hemispheres 116, 132, 176, 179 safety in pregnancy 88 implantation in uterus 75, 78, 85, 86, 96 brainstem 176 cerebral palsy 235 anti-D antibodies 157, 158 preparation of uterus for 78 Braxton Hicks’ contractions 166, 168, 188 cerebrum 176 antibodies 111, 159 blastocyst cavity 86 breastfeeding 42, 207 cervical cap 68 in breast milk 111, 207 blastomeres 75, 84 expressing milk 243 cervix in colostrum 174 bleeding 227 and hormones 175 after birth 206 Rhesus incompatibility 157, 158, 160, after birth 206 milk coming in 174 anatomy 35, 41 230 brain hemorrhage 234 premature babies 151 birth 192 to sperm 216 implantation 76, 86 breasts 34 cervical incompetence 148, 226 anus lochia 243 anatomy 42, 174 cervical-length scan 148 fecal incontinence 241 miscarriage 226 blocked milk ducts 242 dilation 190, 191 hemorrhoids 243 placenta previa 228 cancer 55 fertility problems 216 perineal tears 233 placental abruption 228 changes in pregnancy 134, 136, 138, 175 latent phase of labor 188 sphincter 137 postpartum hemorrhage 240 engorgement 242 mucus 41, 74, 75, 79, 216 Apgar score 10, 197 signs of pregnancy 97 leaking 243 mucus plug 96, 173, 190 areola 42, 174 see also menstruation mastitis 243 polyps 227 changes in pregnancy 136, 138 blood cells milk production 174–5 character traits 53 in late pregnancy 175 production by fetus 103, 129, 146, 159 newborn baby’s 209 cheese, dietary safety 90 Montgomery’s tubercles 134, 138 red blood cells 130, 146, 149 in puberty 43 chemicals, safety 88 arms (fetus) sickle cell disease 237 signs of pregnancy 97 chickenpox 88 development of 95, 122, 142 white blood cells 33, 129 soreness 243 Chlamydia 222, 225 three-dimensional imaging 18–19 blood circulation (fetus) 201 breathing chloasma 135, 136 ultrasound scans 139 in brain 112–13 adaptation of lungs 110 chorion 87, 102 arousal 64–5, 66 Doppler ultrasound 12 formation of respiratory system 152–3 chorionic cavity 87 asexual reproduction 59 embryonic development 87 newborn baby 208 chorionic villi 93, 102, 172 assisted birth 202–3 newborn baby 201, 208 pain relief 197 chorionic villus sampling (CVS) 115 250 chromosomal disorders 236–7 D eggs, dietary safety 90 external os, cervix 41 INDEX and miscarriage 226 dairy products 59, 90 ejaculation 30, 67, 80 eyebrows 159 molar pregnancy 227 Dartos muscle 29 problems 217 eyelashes 159 chromosomes 48–9 dating pregnancy 107, 115 ejaculatory duct 29 eyelids amniocentesis 131 death rates 10 electronic fetal monitoring 191 development of 117 chorionic villus sampling 115 deep vein thrombosis (DVT) 89, 241 embolism, pulmonary 241 fusion 133, 142, 144 genetic recombination 51 delivery see birth embryo 7, 100–101 opening 158, 159, 161 meiosis and mitosis 50–51 delivery date 78, 172, 174 development of 20, 75, 77, eyes sex cells 59 dental care 89 86–7, 92, 184 color 52 sex-linked inheritance 53 dentine, teeth 159 embryonic folding 98–9 color blindness 53 cilia, fallopian tube 84 depression 206, 242 primary germ layers 98 congenital cataracts 237 circumcision 223 dermis 129 embryoblast 85, 86, 87 development of 117, 133, 145, 161 cleft lip and palate 139, 239 desire 64–5, 146, 148 embryonic disk 86 newborn baby 208, 211 clitoris 35, 65 developmental milestones 213 emotions retinopathy of prematurity 234 clones 59 diabetes, gestational 158, 160, 230 after birth 206 clots diamorphine 196 depression 242 F deep vein thrombosis 241 diaphragm, in pregnancy 110 development in first two years 213 face (fetus) pulmonary embolism 241 diaphragms, contraceptive 68 enamel, teeth 159 development of 95, 106, 107, 133, 134 coordination diasonograph 12 endocrine system 27, 184 expressions 14–15 development of 147, 180 diet see food endoderm 98 full-term fetus 181 in first two years 213 digestive system 27 endometrial capillary 86 three-dimensional imaging 14–16 colds 88 development of 104, 137, 167, 185 endometrial vein 86 ultrasound scans 13 colostrum 138, 174, 201, 207 digit abnormalities 239 endometriosis 218 face (mother) color blindness 53 dilation, cervix 190, 191 endometritis 241 pigment changes 135, 136 color vision 161 discharges, vaginal 110, 243 endometrium 35, 40 facial symmetry, and attractiveness 63 columnar epithelium, cervix 41 disorders and diseases 214–43 in early pregnancy 96, 97 fallopian tubes 34 combined test 131 complications in pregnancy 226–31 implantation of embryo 75, 78, 85, 86, 96 anatomy 35, 37 communication fertility disorders 216–17 menstrual cycle 44 assisted conception 217 in first two years 213 genetic disorders 54–5, 236–7 menstruation 74 ectopic pregnancy 85, 227 newborn baby 211 labor and delivery problems 232–3 in third trimester 172 egg in 37, 38–9, 76, 80, 82–3, 84 complications in pregnancy 226–31 mother after delivery 240–43 endothelium, uterus 40 fertility problems 216, 218 conception 60–61, 75, 76, 78–81 newborn baby 234–9 engagement of head 172, 189 laparoscopy 13 assisted conception 217 reproductive disorders 218–23 engorgement falls, safety in pregnancy 89 condoms 68 safety in pregnancy 88 breasts 242 false labor 188 congenital hypothyroidism 235, sexually transmitted diseases erectile tissue 65 fascia, testes 29 237 224–5 Enotonox 196 fat (fetus) congenital infections 88, 235 dizygotic twins 85 Enterococcus fecalis 223 brown fat 147 conjoined twins 114 DNA 48–51 environment, genes and 53 in second trimester 129, 137 connective tissue 86, 87 genetic problems 54 epidermis 129 in third trimester 162, 166, 169 consciousness 163 patterns of inheritance 52 epididymal cysts 222 father constipation 94, 97, 243 dominant genes 52 epididymis 28, 29, 30, 217 bonding with baby 206 contraception 68–9 Donald, Ian 12 epididymo-orchitis 222 parental duties 7 see also oral contraceptive pill Doppler ultrasound 11, 12, 14, 112–13, 149 epidural anesthesia 197 fatigue contractions Down syndrome 237 epigenetics 53 signs of pregnancy 97 afterpains 243 amniocentesis 55, 131 epinephrine (adrenaline) 147 in third trimester 166, 168 birth 192 nuchal translucency scan 11, 115 episiotomy 202, 206, 241 fecal incontinence 241 Braxton Hicks’ 166, 168, 188 screening tests 131 epithelium feet (fetus) false labor 188 drugs cervix 41 development of 134, 149 fetal distress 232 birth control 69 fallopian tubes 37 digit abnormalities 239 first stage of labor 190–91 and cervical mucus 216 erectile tissue 65, 66 newborn baby 209 latent phase of labor 188 pain relief 196 erectile dysfunction 217 three-dimensional imaging 18–19 pain 190 safety in pregnancy 88 erection problems 217 feet (mother) in third trimester 158 ductus arteriosus 238 erogenous zones 64 edema 231 transition phase 191 due date 78, 172, 174 estimated date of delivery 78, female reproductive system 34–45 cooking, safety 90 dysmenorrhea 221 172, 174 disorders 218–21 cord see umbilical cord estradiol 36, 69 femur, fetal growth restriction 229 corona radiata cells 76 E estrogen 36 fertility corpus cavernosum 29, 30 E. coli 220, 231 after birth 201 disorders 216–17 corpus luteum earlobes, genetics 52 contraceptive pill 69 male fertility 79 and hCG 96–7, 189 ears effects of 34 monitoring 79 hormone production 36, 78 development of 117, 144, 165 and lactation 175 fertilization of egg 60–61, 75, 76, 81 and implantation 85 hearing 147, 150 in late pregnancy 189 assisted conception 217 corpus spongiosum 29, 30 three-dimensional imaging 16 menstrual cycle 44 fetal alcohol syndrome 235 cortisol, and lactation 175 eclampsia 229 and morning sickness 130 fetal distress 196, 202, 232 counseling, genetic 55 ectoderm 98 production by corpus luteum 97 fetal growth restriction 229 Cowper’s gland 30 ectopic pregnancy 78, 85, 218, 227 in puberty 43 fetal monitoring 127, 149, 191 cracked nipples 242 edema 231 ethnic groups, genetic problems 55 fetoscopy 13 crawling 213 egg 7, 34, 36 evolution fetus crowning 192 assisted conception 217 of pregnancy 7, 8–9 amniotic fluid 103 crying 211, 213 in fallopian tubes 37, 38–9, 76, 80, of sex 58–9 awareness of surroundings 143, 163, 164 cystic fibrosis (CF) 55, 236, 237 82–3, 84 exercise blood cells 103, 149 cysts fertility problems 216 after delivery 243 brain 116–17, 132, 170, 176–9, 180 epididymal 222 fertilization of 60–61, 75, 76, 81 and fertility problems 216 changing body 20–23, 184–5 molar pregnancy 227 in fetal ovaries 137 in pregnancy 91 changing proportions 142 ovarian 219 formation of twins 85 preparing for birth 91 consciousness 163 cytomegalovirus (CMV) 88 ovulation 43, 44–5, 74, 79, 80 expressing breast milk 243 digestive system 104 cytotrophoblast 85, 86, 87 twins 114 expressions, facial 14–15 ears 117, 144, 150, 165 251 fetus continued FSH see follicle stimulating hormone growth of 95, 142 Huntingdon’s disease 52 engagement of head 172, 189 full-term fetus 172–3, 174 newborn baby 208, 210 hydatiform mole 227 eyes 117, 145, 161 fundus of uterus 35 three-dimensional imaging 14–16 hydrocele 147, 223 INDEX facial appearance 133, 134, 181 contractions 190, 191 healthy eating 91 hydrocephalus 139 in first trimester 72–3 height of 40, 130, 135, 146, 170 hearing hymen 133 full-term fetus 172–3, 174 development of 147, 150 hyperemesis gravidarum 230 genitals 133 G newborn baby 211 hypothalamus hands 149 gamete intrafallopian transfer (GIFT) 217 heart and desire 64 heart 105, 149 Gardnerella vaginalis 220 congenital defects 237, 238 development of 116 imaging techniques 12–13 gas and air 196 development of 94, 105 functions 28, 31, 34, 43 intestines 122 gas exchange fetal distress 232 hypothyroidism, congenital 235, 237 lie 189 in lungs 167 fetal monitoring 127, 149, 191 hysterectomy 218, 219 limbs 122 in placenta 114 murmurs 209, 238 hysterosalpingograms 216 lungs 104 gender 49, 58, 129, 139 newborn baby 208 hysteroscopy 216, 219 measurements 10 genes 48–9 ultrasound scans 139 monitoring placenta 180 and the environment 53 heartburn 110 I movements 124, 136, 138, 142 mutations 54 heel prick test 10 ICSI (intracytoplasmic sperm injection) 11, 217 muscle and fat accumulation 162, 169 patterns of inheritance 52 hemoglobin 130 identical twins 114, 164 nervous system 143, 157 recombination 51 hemorrhage imaging techniques 12–13, 14 nutrition 102, 114 genetics 46–55 brain 234 immune system 26 organogenesis 104 DNA 48–51 postpartum 240 antibodies 159 position in uterus 156, 173, 189 genetic counseling 55 hemorrhoids 243 development of 185 practice breathing 169, 172 genetic disorders 54–5, 236–7 herbs, safety 91 HIV/AIDS 224 reflexes 150 genetic tests 11, 55 hermaphrodites 58 and miscarriage 226 respiratory system 152–3 and miscarriage 226 hernia 238 passing on immunity 111 screening tests 131 patterns of inheritance 52–3 herpes, genital 224, 235 and placenta 9 in second trimester 124–5 sexual reproduction 59 hiccups 136, 142 tolerating fetus 88, 96 sex organs 123, 133, 161 genital herpes 224, 235 hips immunoglobulin 111 skeleton 118–19 genital warts 225 congenital dysplasia of 11, 237, implantation 75, 77, 78, 85, 86, 96 skull 171, 173, 180 genitals 239 implantation bleed 76, 86 teeth 162 development of 123, 133, 185 postnatal checks 209 implants, contraceptive 69 in third trimester 154–5 disorders 218–23 HIV 224 incompetent cervix 148, 226 three-dimensional imaging 14–16 female 34–45 home births 198 incomplete miscarriage 226 ultrasound scans 115, 135, 139 male 28–33 hormones incontinence urinary system 123, 132 newborn baby 209 adrenal glands 147 fecal 241 vernix 158, 159, 162, 172, 181 rubella (German measles) 88, 235 birth control 68, 69 urinary 240, 241 weight gain 173 gestational age 175 breastfeeding 207 inducing labor 175, 202 fiberoptics, fetoscopy 13 gestational diabetes 158, 230 changes after birth 201 inevitable miscarriage 226 fibroids 219 gestation period 8 changes in pregnancy 96–7 infections fimbriae 35, 37, 38 GIFT (gamete intrafallopian transfer) 217 congenital hypothyroidism 235, congenital 235 fingernails glans penis 29, 30, 66 237 infectious diseases 88 growth of 147, 149, 167, 172, 185 glial cells 176, 177 depression 242 uterus 241 newborn baby 208 “glow” of pregnancy 130 emotions after birth 206 wound 241 fingerprints 18, 137, 149 glucose tests 156, 158, 160 female reproductive system 34 infertility 216–17 fingers gonadotropin-releasing hormone (GnRH) 43 fertilization of egg 75 infundibulum, fallopian tubes 37 development of 106, 122, 126, 135, 149 gonorrhea 225 hyperemesis gravidarum 230 inguinal hernia 238 digit abnormalities 239 grasp reflex 145, 147, 150, 210 and implantation 77, 85 inheritance, genetics 52–3 three-dimensional imaging 18–19 gravity, center of 158, 160 in late pregnancy 189 inhibin 31, 43 first trimester 72–123 gray matter, brain 177, 180 and libido 64, 148 insulin 167, 230 fish Group B strep transfer 233 menstrual cycle 44, 76 integrated test 131 dietary safety 90 growth hormone 167 menstrual problems 221 intercostal muscles 174 reproduction 7 growth restriction, fetal 229 and milk production 174, 175 internal os, cervix 41 flu 88 gynecoid pelvis 192 and miscarriage 226 intestines fluid retention 130, 231 morning sickness 94, 128, 130 cystic fibrosis 236 folic acid 10, 78, 91 H and ovaries 36 development of 104, 122 follicle stimulating hormone (FSH) hair 27 and pigmentation changes 136 hernia 238 control of sex hormones 34 development of 185 pituitary gland 116 intracytoplasmic sperm injection (ICSI) 11, 217 menstrual cycle 44 eyebrows and eyelashes 159 polycystic ovarian syndrome 219 intrauterine devices (IUDs) 68, 69, 218, 227 and ovulation 79 lanugo 129, 133, 162, 172, 181 pregnancy tests 96 in-vitro fertilization (IVF) 11, 217 in puberty 43 vellus hair 172 production by placenta 97 iron supplements 130 and testosterone 28, 31 hands puberty 31, 43 ischiopubic ramus 193 follicles, release of egg 44–5, 74 carpal tunnel syndrome 231 second trimester 128 isthmus, fallopian tubes 37 folliculogenesis 44 coordination 147 and sleep 211 fontanelles 120 development of 106, 122, 126, 135, 149 and symptoms of pregnancy 94 J birth of baby 192 digit abnormalities 239 see also individual hormones jaundice, neonatal 151, 235 closure 208 fingerprints 137 human chorionic gonadotropin jaws, newborn baby 208 functions 119, 171, 208 grasp reflex 145, 147, 150, 210 (hCG) joints three-dimensional imaging 16, 180 three-dimensional imaging 18–19 functions 75, 96–7 effects of relaxin on 166 food Hashmi, Zain 55 hyperemesis gravidarum 230 fetal 142 effects on baby 174 hCG see human chorionic gonadotropin and implantation 85, 97 synovial 119 hygiene 90 head in late pregnancy 189 in pregnancy 90–91 bones 120–21, 171, 173, 180 and morning sickness 130 K weaning 212 cephalic presentation 189 pregnancy tests 96 karyotype 48 foramen ovale 238 cephalopelvic disproportion 192, 233 human genome 49 kidneys forceps delivery 202 crowning 192 human papillomavirus (HPV) 225 development of 123, 132 foreskin 29, 223 delivery of 192 human placental lactogen (HPL) 174, ultrasound scans 139 frank breech 189 engagement 172, 189 175 urine production 158 252 kissing 64 premature babies 151, 234 movement, in first two years 213 O INDEX kneeling position, in labor surfactant 144, 151, 152, 165, 234 movements, fetal 124, 136, 138, 142 obturator foramen 193 196 lungs (mother) 76 MRI scans 13, 14 old wives’ tales, sex of baby 139 adaptation of 106, 110 mucus oligohydramnios 228 L breathlessness 146 cervical 41, 74, 75, 79, 216 oral contraceptive pill 10, 62, 69 labia 35, 233 pulmonary embolism 241 nasal congestion 111 organogenesis 104 labor luteinizing hormone (LH) 34 mucus plug 96, 173, 190 orgasm 28, 64, 65, 66, 67 delivery of placenta 200 control of sex hormones 34 Mullerian ducts 123, 133 ossification, bones 17, 118–19 early signs of 190 menstrual cycle 44 multiple births see triplets; twins ovarian cortex 36 false labor 188 and ovulation 79 mumps 222 ovarian ligament 35, 36 fetal distress 232 in puberty 43 muscles 27 ovarian medulla 36 first stage of 190–91 and testosterone 28, 31 contractions 190, 191 ovaries 34 induced labor 175, 202 lymphatic system 26, 123, 185 development of 119, 162, 169, 184 anatomy 35, 36 latent phase 188 fallopian tubes 37 corpus luteum 36, 78, 96–7, 189 multiple births 197 M music 144 cysts 219 pain relief 196–7 McDonald suture 226 mutations, genes 54 development in fetus 123, 127 positions for 196 McVicar, John 12 Mycoplasma hominis 220 fertility problems 216 premature labor 232 male reproductive system 28–33 myelination, nerves 137, 143, 157 fetal 137 transition phase 191 disorders 222–3 myometrium 35, 40, 172 laparoscopy 13 see also birth mammals 7, 8–9 polycystic ovarian syndrome 219 lacrimal glands 117 “mask of pregnancy” 135, 136 N release of egg 44–5, 74 lactation see breastfeeding mastitis 243 nails 27 transplants 11 lactiferous ducts 174, 175 mating systems 62 development of 147, 149, 167, 172, overheating, safety in pregnancy 89 lactose tolerance 59 measles 88 185 oviparous animals 7 language development 213 measurements, fetus 10 newborn baby 208 ovulation 43, 44–5, 74, 80 lanugo hair 129, 133, 162, 172, 181 meconium 232 nasal congestion 111 fertility problems 216 laparoscopy 13, 218, 227 medical advances 10–11 natural selection 59 and mate choice 62 latching on, breastfeeding 207 meiosis 51 nausea monitoring 79 latent phase, labor 188 melanin 135, 136 hyperemesis gravidarum 230 oxygen legs (fetus) melatonin 211 morning sickness 94, 97, 110, 128, cerebral palsy 235 development of 122, 134, 142, 164 menopause 34 130 fetal distress 196 frank breech 189 menorrhagia 220 neck increased demand for in pregnancy 110 three-dimensional imaging 18–19 menstrual cycle 43, 44–5, 76 development of 126 red blood cells 149 ultrasound scans 139 and desire 64 newborn baby 208 oxytocin legs (mother) and mate choice 62 Neisseria gonorrhoea 225 and breastfeeding 175, 207 deep vein thrombosis 241 monitoring fertility 79 neonatal jaundice 235 inducing labor 200, 202 edema 231 problems 220–21 nerves and pair bonding 58, 66 sciatica 231 menstruation 40, 41, 44, 74 carpal tunnel syndrome 231 and sexual intercourse 66 varicose veins 231 dating pregnancy 78 cells 176–7, 180 length of pregnancy 78, 171, 175 puberty 43 myelination 137, 143, 157 P letdown reflex 207 signs of pregnancy 97 neurofibromatosis 236 pain Leydig cells 28, 30, 31, 123 meptazinol 196 sciatica 231 backache 157, 160, 168 LH see luteinizing hormone mesoderm 98 spinal cord 119 contractions 190 libido 64–5, 146, 148 metallic taste, signs of pregnancy nervous system 27 menstrual problems 221 lie, fetus 189 97 consciousness 163 pain relief 196–7 lifestyle, effects on baby 174 metrorrhagia 221 desire and arousal 64–5 pelvic pain 168 ligaments, effects of relaxin 166, midwife 106 development of 99, 184 pair bonding 58, 62, 66 168 home births 198 formation of brain 176–7, 180 palate, cleft 239 light therapy 235 postnatal care 243 reflexes 150 pampiniform plexus 29, 32 lightening 172 milestones 213 neural networks 176 pancreas, cystic fibrosis 236 limb buds 94 milk neural tube 92, 99, 177 panscanners 12 limbs see arms, legs bottle feeding 207 neural tube defects 10, 238 parental duties 7 linea nigra 135, 136 lactose tolerance 59 neurofibromatosis 236 parthenogenesis 59 lip, cleft 239 production in breasts 42 neuroglia 176, 177 paté, safety 90 live-bearing animals 7 see also breastfeeding neurons 176–7, 180 paternity tests 48 liver milk ducts 42 newborn baby 194–5 pectoral muscles 174 blood cell production 159 blocked 242 anatomy 208–9 peg cells, fallopian tubes 37 development of 126 milk teeth 137, 159, 162, 212 Apgar score 197 pelvic floor muscles neonatal jaundice 235 miscarriage 96, 146, 226 blood circulation 201, 208 fecal incontinence 241 newborn baby 209 missed miscarriage 226 early responses and progress 210–11 Kegel exercises 91, 206 premature babies 151 mitosis 50 neonatal screening 237 urinary incontinence 241 liver, dietary safety 90 molar pregnancy 227 problems 234–9 pelvic inflammatory disease (PID) 218 lobules monitoring nipples pelvis breasts 42, 174, 175 fetal 127, 149, 191 anatomy 42 birth of baby 192 testes 30 placenta 180 breastfeeding 174 cephalopelvic disproportion 192, 233 lochia 241, 243 premature babies 151 changes in pregnancy 136, 138, 175 effects of relaxin 168, 172 lumen monozygotic twins 85 cracked 242 engagement of head 189 cervix 41 Montgomery’s tubercles 134, 138 latching on 207 and evolution of pregnancy 9 fallopian tubes 37 morning-after pill 69 in puberty 43 pain 168 lungs (fetus) morning sickness 94, 97, 110, 128, 130 nongonococcal urethritis (NGU) 225 shapes 192 alveoli 169, 170 hyperemesis gravidarum 230 nose penis 28, 30 cystic fibrosis 236 morula 75, 82, 84 development of 133, 152 anatomy 29 development of 104, 137, 147, 152–3, motor neurons 176 nasal congestion 111 balanitis 223 167 mouth nuchal translucency scan 11, 115 ejaculation 67 inhalation of amniotic fluid 166 cleft lip and palate 139, 239 nucleotides, DNA 48 erectile dysfunction 217 newborn baby 208 development of 152 nutrition, fetus 102, 114 erection 65, 66 practice breathing 169, 172 yawning 142, 156 see also food sexual intercourse 66 253 perimetrium 40 birth control 68, 69 retained placenta 232 skin color, genetics 52 perinatal care, medical advances 11 and breastfeeding 175 retina 117, 161 skull 120–21, 173, 180 perineal tears 233 effects of 34 retinopathy of prematurity 234 birth of baby 192 INDEX perineum 35 in late pregnancy 189 Rhesus incompatibility 157, 158, 160, 230 development of 119 soreness 243 and menstruation 44, 76. 220 rhinitis, pregnancy 111 fontanelles 16, 119, 120, 171, 180, 192, 208 peristalsis, fallopian tubes 37 production by corpus luteum 97 ribs 174 newborn baby 208 peritoneum 35 in puberty 43 rooting reflex 150, 210 sleep pethidine 196 and stretchmarks 148 round ligament of uterus 35 fetus 166 phenylketonuria (PKU) 10, 55, 236, 237 prolactin rubella (German measles) 88, 235 newborn baby 211 pheromones 63 and libido 148 in pregnancy 89 phototherapy 235 and milk production 174, 175, 207 S smell, sense of 93 piezo-electric crystals, ultrasound 12 prolapse safety in pregnancy 88–9 smiling, newborn baby 211 pigment changes 135, 136, 243 umbilical cord 196, 232 “savior” siblings 55 smoking 88, 174 Pinard stethoscope 191 uterus 240 scans see ultrasound social development 213 pineal gland 211 vagina 240 Schwann cells 143 somites 94, 99 pitocin 202 prostaglandins 202, 221 sciatica 231 sonicaid 191 pituitary gland prostate gland 28, 29, 30 screening tests 110, 131, 237 sound waves, ultrasound 12 and breastfeeding 207 prostatitis 223 scrotum 32 sperm development of 116, 167 proteins, DNA and 48, 50 anatomy 29 abnormalities 33 and puberty 31, 43 psychosis, puerperal 242 descent of testes 147, 161 anatomy 33 and reproductive system 28, 34 puberty hydrocele 223 antibodies to 216 placenta 7 female 43 varicocele 217, 222 assisted conception 217 birth of baby 192 male 31 second trimester 124–53 capacitation 67, 80 chorionic villus sampling 115 pubic hair 43 secondary follicle 36 and cervix 41 delivery of 200 pubic symphysis joint 35 secretory lobules, breasts 42, 174, 175 competition 58 development of 75, 77, 92, 95, 102, 114 birth of baby 192 semen 28 ejaculation 67, 80 in early labor 190 loosening 172 analysis of 33 fertility 79 and evolution of pregnancy 9 pelvic pain 168 ejaculation 67, 80 fertility problems 217 hormones 97 puerperal psychosis 242 and prostate gland 30 fertilization of egg 60–61, 75, 76, 81 and immune system 111 pulmonary embolism (PE) 241 seminal vesicles 28, 29, 30 intracytoplasmic sperm injection (ICSI) 11, monitoring 180 pyloric stenosis 238 seminiferous tubules 28, 30, 32 217 placenta accreta 232 senses production of (spermatogenesis) 28, 32–3 placenta previa 139, 228 Q consciousness 163 and sex of baby 49 placental abruption 228 quadruple test 131 hearing 147, 150, 211 spermatic cord, testicular torsion 223 retained placenta 232, 240 quadruplets newborn baby 211 spermatids 33 in third trimester 169, 170 length of pregnancy 175 smell 93 spermatocytes 32, 33 twins 114 three-dimensional imaging 19 taste 93, 97 spermatogonia 32 ultrasound scans 139 quickening 124, 136, 138 vision 53, 147, 161, 211 spicules 120 villi 94, 95 quintuplets, length of pregnancy 175 sensory neurons 176 spina bifida 10, 78, 139, 238 polycystic ovarian syndrome 216, 219 serosa, fallopian tubes 37 spinal block 197 polydactyly 239 R Sertoli cells 28, 31, 32, 123 spinal cord polyhydramnios 228 radiation, safety in pregnancy 89 sex 56–69 development of 119, 126, 176 polyps recessive genes 52 attractiveness 62–3 neural tube defects 238 cervical 227 rectum 123 birth control 68–9 spine 99 uterine 219 fecal incontinence 241 desire and arousal 64–5, 148 changes in pregnancy 160 population growth 6 prolapse 240 evolution of 58–9 development of 119 positive assortative mating 62 red blood cells intercourse 66–7 ultrasound scans 139 postnatal care 11, 243 increase in pregnancy 130 in pregnancy 91 spleen, blood cell production 159 postnatal checkups 209 production of 146, 149 sex of baby 49, 58, 129, 139 sport, safety in pregnancy 91 postpartum depression 206, 242 sickle cell disease 237 sex cells 58, 59 spotting, signs of pregnancy 97 postpartum hemorrhage (PPH) 240 reflexes 210 see also eggs; sperm squatting position, in labor 196 posture development of 142, 150 sex-linked inheritance 53 Staphylococcus 220, 243 backache 157, 160 grasp reflex 145, 147, 150, 210 sex organs see reproductive system startle reflex 210 and blood pressure 130 hiccuping 142 sexual reproduction 59 stem cells 93, 99 center of gravity 158, 160 letdown reflex 207 sexually transmitted diseases (STDs) 224–5 stepping reflex 210 in third trimester 160 rooting reflex 150, 210 shoulders stethoscope, Pinard 191 preeclampsia 229 startle reflex 210 birth of 192, 193 stitches preconception care, medical advances 10 stepping reflex 210 shoulder dystocia 233 cervical incompetence 226 pregnancy tests 10, 76, 92, 96 suckling reflex 150, 167, 201, 207 “show” 190 episiotomy 202 premature babies 146, 151, 232 regeneration 59 sickle cell disease 55, 237 perineal tears 233 cervical-length scan 148 reheating food 90 sign language 213 stomach, pyloric stenosis 238 length of pregnancy 175 relaxin 43 silastic extractor 202 strangulated hernia 238 problems 234 and backache 160 sitting position, in labor 196 streptococcus viability threshold 175 in late pregnancy 166, 168 skeletal system 27 congenital infections 235 prenatal care reproduction 6–7 skeleton see bones Group B strep transfer 233 in first trimester 110 evolution of sex 58–9 skin (baby) wound infection 241 medical advances 11 reproductive system 26 newborn baby 209 stress, safety in pregnancy 89 in third trimester 160, 166 development of 123, 133, 185 premature baby 151 stress incontinence 240, 241 prenatal classes 160 disorders 218–23 skin (fetus) stretchmarks 146, 148, 243 preovulatory follicles 36 female 34–45 development of 95, 185 striae gravidarum 148 prepuce 29 male 28–33 structure 129 stroke, cerebral palsy 235 primary follicle 36 reptiles, reproduction 7 in third trimester 167 stroma, breasts 174, 175 primary germ layers 98 respiratory distress syndrome 234 vernix 158, 159, 162, 172, 181 subcutaneous fat 129, 137 primitive streak 98 respiratory system 26 skin (mother) 27 suckling reflex 150, 167, 201, 207 primordial follicles 36 adaptation of lungs 106, 110 changes after delivery 243 supplements 91 progesterone 36 formation of 104, 152–3, 185 pigment changes 135, 136, 243 folic acid 10, 78, 91 after birth 201 see also breathing stretchmarks 146, 148, 243 iron 130 254 surfactant 167 trimesters position of fetus in 156, 173, 189 white blood cells INDEX functions 152 first 72–123 position of placenta 139, 228 production of 129 premature babies 151, 234 second 124–53 postpartum hemorrhage 240 semen analysis 33 production of 144, 147, 165 third 154–85 prolapse 240 womb see uterus sutures, skull 180, 192, 208 triple test 131 retained placenta 232 work, safety in pregnancy 89 swaddling 209 triplets 231 starting to “show” 130 wound infection 241 sweeping the membranes 202 length of pregnancy 175 see also contractions wrist symmetry, and attractiveness 63 premature labor 232 carpal tunnel syndrome 231 symphysis pubis dysfunction 168 three-dimensional imaging 19 V newborn baby 208 symptoms of pregnancy 94, 97, 128 trisomy 21 237 vaccinations, safety in pregnancy 88 synapses 143 trophoblast 75, 86, 87 vacuum delivery 202 X syncytiotrophoblast 77, 85, 86, 87, tunica vaginalis 29 vagina 34 X chromosomes 49, 53 96 Turner syndrome 237 anatomy 35, 41 Turner syndrome 237 syndactyly 239 twins 114 bacteria 220 X-rays, safety in pregnancy 89 synovial joints 119 complications of pregnancy 231 birth of baby 193 syphilis 224 delivery 197 cervical-length scan 148 Y formation of 85 development in fetus 123, 133 Y chromosomes 49, 53 T genetics 52 discharges 110, 243 yawning 142, 156 tail 99 identical twins 114, 164 in labor 191 yolk sac 77, 86, 87, 94, 98, 101, 102 taste, sense of 93, 97 length of pregnancy 169, 175 perineal tears 233 taste buds 129 nonidentical twins 45, 114 prolapse 240 Z tears, perineal 233 three-dimensional imaging 19 sexual intercourse 66 zona pellucida 84–5 teeth twin-twin transfusion syndrome 114 soreness 243 zygote 75, 82–3, 84 dental care 89 ultrasound scans 13 ultrasound scans 146 development of 135, 156, 162, 185 weight 169 vulvovaginitis 220 milk teeth 159 see also bleeding teething 212 U varicocele 217, 222 tooth buds 137 ultrasound 10, 11, 12–13 varicose veins 231 temperature cervical-length scan 148 vas deferens 29, 30, 217 changes at ovulation 79 Doppler 11, 12, 14, 112–13, 149 veins newborn baby 209 first scan 107, 115 deep vein thrombosis 89, 241 safety in pregnancy 89 nuchal translucency scan 11, 115 varicocele 217, 222 TENS machines 197 three-dimensional imaging 12, 13, 14 varicose veins 231 test tube babies 11 20-week scan 135, 139 vellus hair 172 testes 30 vaginal 146 vernix 158, 159, 162, 172, 181 anatomy 29 umbilical cord vertebrae 99 descent of 147, 161 blood vessels 114, 165, 200, 229 changes in pregnancy 160 development in fetus 123 cutting 200 development of 119 epididymo-orchitis 222 development of 94, 98 ultrasound scans 139 hydrocele 223 during birth 192 viability threshold, premature babies 175 neonatal screening 237 in early labor 190 villi, placenta 94, 95 production of sperm 28, 32–3 newborn baby 209 viruses testicular torsion 223 prolapse 196, 232 genital herpes 224 testicular artery 29 in third trimester 173 genital warts 225 testosterone 28 ureters 29 HIV/AIDS 224 and desire 64 urethra 29, 35 immune system 111 fertility problems 217 urethritis, nongonococcal 225 vision male puberty 31 urinary system 26 color blindness 53 in women 34 development of 123, 132, 185 color vision 161 thalamus 159, 163 urinary tract infections 231 development of 147, 161 third trimester 154–85 urination newborn baby 211 threatened miscarriage 226 by fetus 129, 158, 167 vitamin K supplements 197 three-dimensional (3D) imaging 12, 13 incontinence 240, 241 viviparous animals 7 throat, development of 152 problems after delivery 243 vocal cords 31 thrombosis, deep vein 89, 241 signs of pregnancy 97 voice thrush 220, 223 in third trimester 166, 172 breaking 31 thumb sucking 142, 147, 171 urine tests 11, 156, 160 recognizing mother’s 150 thymus gland 208 uterine artery 229 vomeronasal organ 63 thyroid gland, congenital hypothyroidism uterus 34 vomiting 235, 237 abnormalities 221 hyperemesis gravidarum 230 thyroxine, and lactation 175 after birth 206 morning sickness 94, 97, 110, 128, 130 toes afterpains 243 pyloric stenosis 238 development of 134, 149 amniocentesis 131 vulvovaginitis 220 digit abnormalities 239 anatomy 35, 40–41 three-dimensional imaging 18–19 birth of baby 192–3 W tongue, taste buds 129 development in fetus 123, 133 walking 213 tooth buds 137 endometriosis 218 warts, genital 225 toxoplasmosis 88 fertility problems 216 water birth 198–9 trachea 152 fibroids and polyps 219 water, breaking 190 transducers, ultrasound 12 fundal height 146 weaning 212 transgenerational inheritance 53 growth of 40, 78, 128, 135, 170, 172 weight transition phase, labor 191 implantation in 75, 77, 78, 85, 86, 96 fetus 162, 173 transplants, ovarian 11 infection 241 gain in pregnancy 90, 92 transverse lie 189 laparoscopy 13 loss after delivery 243 travel, safety in pregnancy 89 menstrual cycle 76 newborn baby 208, 210 Treponema pallidum 224 menstruation 40, 44, 74 twins 169 Trichomonas vaginalis 220, 225 placental abruption 228 Wharton’s jelly 114 255 ACKNOWLEDGMENTS

Dorling Kindersley would like to thank 53 Corbis: Bernd Vogel (cla). Getty Images: JGI (cl); Edelmann (cr). 134 Science Photo Library: Neil Bromhall Library: Dr. Arthur Tucker (cl). 218 Science Dr. Paul Moran of the Royal Victoria Infirmary, Steve Allen (cra); IMAGEMORE Co.,Ltd. (tl). Science (cr); BSIP, Margaux (cl); Edelmann (bl). 135 Alamy Images: Photo Library: CNRI (tr, cl); Sovereign, ISM (b). Newcastle, for providing ultrasound scans, as Photo Library: Richard Hutchings (crb). 55 Press Oleksiy Maksymenko Photography (bl). Science Photo 219 Photolibrary: Medicimage (ca). Science Photo Association Images: John Giles/PA Archive (br). Science Library: P. Saada / Eurelios (br). 138 Alamy Images: Library: Gustoimages (crb); Dr. Najeeb Layyous (bl/ well as the women who gave permission for Photo Library: BSIP, Laurent H.americain (bl). 56–57 Science Photo Library (fcr); Chris Rout (tr); Picture photo); John Radcliffe Hospital (br). 220 Science Photo their scans to be used—Emma Barnett, Paula Science Photo Library: Susumu Nishinaga. 57 Science Partners (bc, br). Science Photo Library: Gustoimages Library: Eye of Science (tc); Moredun Scientific Ltd (cl); Binney, Sophie Lomax, and Katie Marshall. Sarah Photo Library: Susumu Nishinaga (cr). 58 Getty Images: (tc); (cr). 139 Corbis: Ian Hooton/Science Photo Library Pasieka (cr). 221 Alamy Images: Gabe Palmer (tr). Smithies and Jenny Baskaya carried out Priscilla Gragg (cl). Wellcome Images: BSIP (b). 58–59 (bc). Science Photo Library: (cl); Living Art Enterprises, Science Photo Library: Michael W. Davidson (br). additional picture research, and Laura Getty Images: DEA / G. Dagli Orti. 58–69 Science Llc (ca). 140–141 Science Photo Library: Neil Bromhall. 222 eMedicine.com: Image reprinted with permission Wheadon provided editorial assistance. Photo Library: Susumu Nishinaga. 59 Getty Images: 142 Alamy Images: Nic Cleave Photography (b). Science from eMedicine.com, 2010. Available at: http:// Darrell Gulin (bl). Science Photo Library: Ken M. Highfill Photo Library: Edelmann (tl). 143 Getty Images: emedicine.medscape.com/article/382288-overview (bl). (cra). 60–61 Getty Images: Yorgos Nikas. 62 Getty Photolibrary/Derek Bromhall (tr). Science Photo Science Photo Library: Pasieka (tr). 223 Science Photo Images: Jupiterimages, Brand X Pictures (cr); PHOTO 24 Library: (tl); Thomas Deerinck, NCMIR (br). 144 Getty Library: CNRI (cr); Dr. P. Marazzi (tl). 225 Science Photo

ACKNOWLEDGMENTS Picture credits The publisher would like to thank the following for (c); Beth Davidow (cl). Science Photo Library: Images: Tom Grill (bl). Science Photo Library: Steve Library: Dr. Linda Stannard, UCT (cla); (cr). 227 Science their kind permission to reproduce their photographs: Professors P.M. Motta & J. Van Blerkom (bl); Gschmeissner (cra); Edelmann (cla, br). 145 Dept of Fetal Photo Library: Zephyr (tl). 229 Courtesy of Dr. John Gustoimages (tl). 63 Getty Images: Image Source (bl). Medicine, Royal Victoria Infirmary: (br). Science Kingdom, Placenta Clinic, Mount Sinai Hospital, (Key: a-above; b-below/bottom; c-center; f-far; l-left; © 2008 Little et al. This is an open-access article Photo Library: Steve Gschmeissner (bl); CIMN, ISM (cl). University of Toronto, Canada: (cr/doppler scans). r-right; t-top) distributed under the terms of the Creative 148 Science Photo Library: Dr. P. 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