Chapter Chapter 1 / Emergency Management: Evaluation of the Critically Ill or Injured Child • 1 Pregnancy and 1 Prenatal Care ᭿ PREGNANCY Terms and Definitions From the time of fertilization until the pregnancy is Pregnancy is the state of having products of concep- 8 weeks along (10 weeks gestational age [GA]), the tion implanted normally or abnormally in the uterus conceptus is called an embryo. After 8 weeks until or occasionally elsewhere. Pregnancy is terminated the time of birth, it is designated a fetus. The term by spontaneous or elective abortion or delivery. A infant is used for the period between delivery and 1 myriad of physiologic changes occur in a pregnant year of age. Pregnancy is divided into trimesters. The woman, which affect every organ system. first trimester lasts until 12 weeks but is also defined as up to 14 weeks GA, the second trimester from 12 Diagnosis to 14 until 24 to 28 weeks GA, and the third trimester from 24 to 28 weeks until delivery. An In a patient who has regular menstrual cycles and is infant delivered prior to 24 weeks is considered to sexually active, a period delayed by more than a few be previable, from 24 to 37 weeks is considered days to a week is suggestive of pregnancy. Even at preterm, and from 37 to 42 weeks is considered term. this early stage, patients may exhibit signs and symp- A pregnancy carried beyond 42 weeks is considered toms of pregnancy. The classic finding of “morning postdate or postterm. sickness” can begin this early and often continues Gravidity (G) refers to the number of times a through 12 to 16 weeks of gestation. On physical woman has been pregnant, and parity (P) refers to examination, a variety of findings indicate pregnancy the number of pregnancies that led to a birth beyond (Table 1-1). 20 weeks GA or of an infant weighing more than Many over-the-counter (OTC) urine pregnancy 500g. A more specific designation of pregnancy out- tests have a high sensitivity and will be positive comes divides them into term and preterm deliver- around the time of the missed menstrual cycle. These ies, number of abortuses, and number of living urine tests and the hospital laboratory serum assays children. This is known as the TPAL designation. A test for the beta subunit of human chorionic woman who has given birth to one set of preterm gonadotropin (b-hCG). This hormone produced by twins, one term infant, and with two miscarriages the placenta will rise to a peak of 100,000mIU/mL would be a G4 P1-1-2-3. A multiple gestation is just by 10 weeks of gestation, decrease throughout one delivery but obviously may change the number the second trimester, and then level off at approxi- of living children by more than one. In this designa- mately 20,000 to 30,000mIU/mL in the third tion, abortuses includes both therapeutic and spon- trimester. taneous abortions. A viable pregnancy can be confirmed by ultra- sound, which may show the gestational sac as early as 5 weeks, or at a b-hCG of 1500 to 2000mIU/mL, Dating of Pregnancy and the fetal heart as soon as 6 weeks, or a b-hCG The GA of a fetus is the age in weeks and days of 5000 to 6000mIU/mL. measured from the last menstrual period (LMP). 2 • Blueprints Obstetrics & Gynecology ᭿ TABLE 1-1 include pregnancy landmarks such as auscultation of the fetal heart (FH) at 20 weeks by nonelectronic Signs and Symptoms of Pregnancy fetoscopy or at 10 weeks by Doppler ultrasound, Signs as well as maternal awareness of fetal movement Bluish discoloration of vagina and cervix (Chadwick’s or “quickening,” which occurs between 16 and 20 sign) weeks. Softening and cyanosis of the cervix at or after 4 weeks (Goodell’s sign) Physiology of Pregnancy Softening of the uterus after 6 weeks (Ladin’s sign) Breast swelling and tenderness Cardiovascular Development of the linea nigra from umbilicus to During pregnancy, cardiac output increases by 30% pubis to 50%. Most increases occur during the first trimester, with the maximum being reached between Telangiectasias 20 and 24 weeks gestation and maintained until Palmar erythema delivery. Systemic vascular resistance decreases Symptoms during pregnancy, resulting in a fall in arterial blood Amenorrhea pressure. This decrease is most likely due to the ele- Nausea and vomiting vated progesterone leading to smooth muscle relax- Breast pain ation. There is a decrease in systolic blood pressure Quickening—fetal movement of 5–10mm Hg and in diastolic blood pressure of 10–15mm Hg that nadirs at week 24. Between 24 weeks gestation and term, blood pressure slowly returns to prepregnancy levels but should never Developmental age (DA) is the number of weeks and exceed them. days since fertilization. Because fertilization usually occurs about 14 days after the first day of the prior Pulmonary menstrual period, the GA is 2 weeks more than the There is an increase of 30% to 40% in tidal volume DA. (VT) during pregnancy (Figure 1-1) despite the fact Classically, Nägele’s rule for calculating the esti- that the total lung capacity is decreased by 5% due mated date of confinement (EDC), or estimated date to the elevation of the diaphragm. This increase in VT of delivery (EDD), is to subtract 3 months from the decreases the expiratory reserve volume by about LMP and add 7 days. Thus, a pregnancy with an LMP 20%. The increase in VT with a constant respiratory of 4/13/02 would have an EDC of 1/20/03. Exact rate leads to an increase in minute ventilation of 30% dating uses an EDC calculated as 280 days after a to 40%, which in turn leads to an increase in alveo- certain LMP. If the date of ovulation is known, as in lar (PAo2) and arterial (Pao2) Po2 levels and a decrease assisted reproductive technology (ART), the EDC in PAco2 and Paco2 levels. can be calculated by adding 266 days. This dating can Paco2 decreases to approximately 30mm Hg by 20 be confirmed and should be consistent with the weeks gestation from 40mm Hg prepregnancy. This examination of the uterine size at the first prenatal change leads to an increased CO2 gradient between appointment. mother and fetus and is likely caused by elevated With an uncertain LMP, ultrasound is often used progesterone levels that either increase the respira- to determine the EDC. Ultrasound has a level of tory system’s responsiveness to CO2 or act as a uncertainty that increases during the pregnancy but primary stimulant. Dyspnea of pregnancy occurs in it is rarely off by more than 7% to 8% at any GA. A 60% to 70% of patients. This is possibly secondary to safe rule of thumb is that the ultrasound should not decreased Paco2 levels, increased VT, or decreased differ from LMP dating by more than 1 week in the total lung capacity (TLC). first trimester, 2 weeks in the second trimester, and 3 weeks in the third trimester. The dating done with Gastrointestinal crown-rump length in the first half of the first Nausea and vomiting occur in more than 70% of trimester is probably even more accurate, to within pregnancies. This has been termed “morning sick- 3 to 5 days. ness” even though it can occur anytime throughout Other measures used to estimate gestational age the day.These symptoms have been attributed to the Chapter 1 / Pregnancy and Prenatal Care • 3 TLC–total lung capacity VC–vital capacity 3.0 IC–inspiratory capacity FRC–functional residual capacity IC IRV–inspiratory reserve volume 2.0 IC IRV IRV VC TV–tidal volume ERV–expiratory reserve RV– residual volume Liters 1.0 TLC TV TV ERV ERV 0 RV RV FRC -1.0 Nonpregnant Late pregnancy Figure 1-1• Lung volumes in nonpregnant and pregnant women. elevation in estrogen, progesterone, and hCG. The tion. Although 7% to 8% of patients’ platelets may nausea and vomiting should routinely resolve by be between 100 and 150 million/mL, a drop in the 14 to 16 weeks gestation. During pregnancy, the platelet count below 100 million/mL or over a short stomach has prolonged gastric emptying times, and time period is not normal and should be investigated the gastroesophageal sphincter has decreased tone. promptly. Together, these changes lead to reflux and possibly Pregnancy is considered to be a hypercoagulable combine with decreased esophageal tone to cause state, and the number of thromboembolic events ptyalism, or spitting, during pregnancy. The large increases. There are elevations in the levels of fi- bowel also has decreased motility, which leads to brinogen and factors VII–X. However, the actual increased water absorption and constipation. clotting and bleeding times do not change. The increased rate of thromboembolic events in preg- Renal nancy may be secondary to an increase in venous The kidneys actually increase in size and the ureters stasis and vessel endothelial damage. dilate during pregnancy, which may lead to increased rates of pyelonephritis. The glomerular filtration rate Endocrine (GFR) increases by 50% early in pregnancy and is Pregnancy is a hyperestrogenic state. The increased maintained until delivery. As a result of increased estrogen is produced primarily by the placenta, with GFR, blood urea nitrogen and creatinine decrease by the ovaries contributing to a lesser degree. Unlike about 25%. An increase in the renin-angiotensin estrogen production in the ovaries, where estrogen system leads to increased levels of aldosterone. This precursors are produced in ovarian theca cells and ultimately results in increased sodium resorption. transferred to the ovarian granulosa cells, estrogen in However, plasma levels of sodium do not increase the placenta is derived from circulating plasma-borne because of the simultaneous increase in GFR.