Twin Pregnancy a Complicating Journey for Both Mothers and Babies: Elaborate Review
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International Journal of Basic & Clinical Pharmacology Shelke PS et al. Int J Basic Clin Pharmacol. 2020 Apr;9(4):674-682 http:// www.ijbcp.com pISSN 2319-2003 | eISSN 2279-0780 DOI: http://dx.doi.org/10.18203/2319-2003.ijbcp20201196 Review Article Twin pregnancy a complicating journey for both mothers and babies: elaborate review Pallavi Sitaram Shelke, Pradnya Nilesh Jagtap* Department of Pharmacology Department, PDEA’s S.G.R.S. College of Pharmacy, Saswad, Maharashtra, India Received: 18 January 2020 Revised: 04 March 2020 Accepted: 05 March 2020 *Correspondence: Dr. Pradnya Nilesh Jagtap, Email: [email protected] Copyright: © the author(s), publisher and licensee Medip Academy. This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. ABSTRACT Pregnancy, also known as gestation, is the time during which one or more offspring develops inside a woman. A multiple pregnancy involves more than one offspring, such as with twins. Pregnancy can occur by sexual intercourse or assisted reproductive technology. A pregnancy may end in a live birth, abortion, or miscarriage, though access to safe abortion care varies globally. Research shows that 10 percent to 15 percent of all singleton births may have started off as twins; often one is lost early in pregnancy in a phenomenon known as "vanishing twin syndrome." Multiple pregnancy occurs when two or more ova are fertilized to form dizygotic (non-identical) twins or a single fertilised egg divides to form monozygotic (identical) twins. In the U.S, about three in every 100 pregnant women give birth to twins or triplets, according to the Mayo Clinic in Rochester, Minn. And by many accounts, twin pregnancies are on the rise. This review provides a blessful information to understand what happening when expecting twins and also help to cope with pregnancy related complications and give twins the best start in life. Keywords: Birth defects, Complications, Health concern, Risk factors, Twin or multiple gestation INTRODUCTION Twin or multiple births are much more common today than they were in the past. Pregnancy is a happy and joyous time for many women. It can also be a challenging time of life as the mother’s body goes through numerous changes in order to create and support the development of a new life.1 A woman can be pregnant with twins or multiples either by chance (genetic factors) or due to some medical treatments. There is no sure-shot way of getting pregnant with twins. Multiple pregnancies, as the name suggests, is a pregnancy in which the mother carries more than one foetus in the uterus.2 The most common type of multi-fetal pregnancy is twins, where there are two babies developing simultaneously in the womb. Rarely, there are three or four foetuses developing in a single pregnancy.3 Figure 1: Twin pregnancy overview journey.4 International Journal of Basic & Clinical Pharmacology | April 2020 | Vol 9 | Issue 4 Page 674 Shelke PS et al. Int J Basic Clin Pharmacol. 2020 Apr;9(4):674-682 General odds of having twins from one egg have been born with opposite sexes. The probability of this is extremely small- multiples having The 21st-century statistics show that the possibility of different genders is universally accepted as a sound basis having twins are 3%, i.e. 3 in 100 among the general for a clinical determination, which multiples do not stem population. Figures also show that there is an increase of from one egg.7 almost 61% from the early 1980s. A much recent update from the US National Center for Health Statistics says Fraternal twins/dizygotic twins that the twin birth rate is 33.9 per 1000 live births.5 Fraternal twins are also referred to as dizygotic twins, CLASSIFICATION non-identical twins or two-egged twins. They develop from two different eggs; each is fertilized by separate sperm cells. They share approximately 50 percent of their Twin pregnancy genes, similar to any other siblings born at different times, who have the same biological mother and father. This means, that the chances of them looking alike are the same as the likelihood of any other siblings. They Identical twins / Fraternal twins / may look very much alike- or they may look very Monozygotic twins (30%) Dizygotic twins (70%) different. Figure 2: Classification of twin pregnancy. Fraternal twins can be either gender or a combination of boy and girl. There are some patterns of twinning that are Identical twins/monozygotic twins exceedingly rare. In rare cases, a woman’s eggs are fertilized at different times with two or more acts of Identical twins are also referred to as monozygotic twins sexual intercourse. This is known as superfetation and or one-egg twins. They are the result of a single egg, occurs when a woman continues ovulating after 8 fertilized by a single sperm cell. Very early in becoming pregnant. development, the egg divides, resulting in two individuals with the same DNA. Even though they may look There have also been instances of fraternal twins with identical, they have their own unique traits. This is due to different fathers. This occurs when a woman releases various growth conditions in the womb. About 25 percent multiple eggs and has sexual relations with more than one of all identical twins may be mirror twins. They are a partner. If an egg is fertilized by sperm from one man, subset of identical twins and are identical twins with and then another egg is fertilized by sperm from another opposite features. These mirrors are reflections of each man, the result is fraternal twins with different fathers. other which means that the left side of one twin, matches This phenomenon is termed heteropaternal the right side of the other twin. They may possess superfecundation and these fraternal twins are genetically matching or almost matching fingerprints and share the half-siblings and share approximately 25 percent of their 8 same DNA. Organs and birthmarks can be placed on DNA. opposite sides of their bodies and one twin may be right- handed, whereas the other is left-handed. They result from a late split of the fertilized egg.6 Figure 4: Determining chorionicity and amnionicity.9 Figure 3: Main types of twin pregnancy.6 Conjoined twins There are some patterns of identical twinning that are Conjoined twins are also referred to as Siamese twins. exceedingly rare: in extremely rare cases twins that stem Conjoined twins are identical twins whose bodies are International Journal of Basic & Clinical Pharmacology | April 2020 | Vol 9 | Issue 4 Page 675 Shelke PS et al. Int J Basic Clin Pharmacol. 2020 Apr;9(4):674-682 joined together at birth. This occurs when the fertilized FACTORS THAT DETERMINE THE CHANCES egg fails to separate completely because they split very OF HAVING TWINS late in development. Most conjoined twins are also mirror twins. Identical twins could only happen by sheer chance. But certain factors might influence the chances of having There is a type of conjoined twin that is sometimes fraternal twins.13-15 referred to as parasitic twin. The condition is called Twin Reversed Arterial Perfusion (TRAP). Parasitic twins Family history/heredity develop asymmetrically, with a smaller, less formed twin dependent on the stronger, larger twin. A variation of A history of multiple pregnancies in the family increases parasitic twinning is a fetus in fetu, where an abnormally the chances of it repeating.13 formed mass of cells grows inside the body of its identical twin. It survives during pregnancy, and even Ethnicity/race occasionally after birth, by tapping directly into the blood supply of the host twin.10 Women origin is also believed to have a strong influence on their chance of having twins. Historically, women belonging to certain ethnicities stand a higher chance of having multiple pregnancies.13 Type of body (height/weight) Although strange, it is said that taller women are more likely than shorter ones to conceive with twins. Also, heavier women have higher chances than thinner women. A research study published by the American College of Obstetrics and Gynaecology states that the increasing rates of multiple births are due to increased rates of obesity. It is found that women with a body mass index (BMI) of 30 and above are more likely to produce twins. This holds for only fraternal twins.14,15 Maternal age 11 Figure 5: Conjoined twins. The chance of having twins or more babies may increase with advancing age. Women above 35 years produce Semi identical twins more FSH (follicle-stimulating hormone) than younger women.16 This hormone allows the ovaries to release Semi identical twins are also referred to as polar body eggs for ovulation. The higher the hormone levels, the twins or half identical twins. Semi identical twins are more the eggs released during ovulation are, thereby types of twins, who share half their genes in common resulting in multiple fetuses. from the mother and the other half different from two separate sperm cells. This occurs when two sperm More pregnancies fertilize one egg, which then later splits. They share some features of identical twins and some features of fraternal If women had multiple pregnancies before, there may be twins. These twins will look very much alike but aren’t a a high chance of producing twins. The probability of 100 percent DNA match. An embryo created this way twins might also improve with the increasing number of 11 doesn’t usually survive, but a few cases are known. pregnancies.17 Mixed chromosome twins COMPLICATIONS IN TWIN OR MULTIPLE PREGNANCY Mixed chromosome twins are also referred to as chimeras.