Sonography provides invaluable information regarding fetal anatomy, growth, and well-being, and most women in the United States have at least one prenatal sonographic examination during pregnancy (American College of Obstetricians and Gynecologists, 2016h). Continuing trends suggest that the number of these examinations performed per pregnancy is increasing. Siddique and associates (2009) reported that the average number rose from 1.5 in 1995 through 1997 to 2.7 almost 10 years later. his trend was noted in both high-and low-risk pregnancies. he actual clinical utility of this increased use in pregnancy has not been demonstrated, and it is unclear that the cost-benefit ratio is justified (Washington State Health Care Authority, 2010). The American College of Obstetricians and Gynecologists (20e16h) has concluded that sonography should be performed only when there is a valid medical indication and under the lowest possible ultrasound exposure setting. The College further states that a physician is not obligated to perform sonography without a specific indication in a low-risk patient, but that if she requests sonographic screening, it is reasonable to honor her request.
If initial results were normal, most tests need not be repeated. Hematocrit or hemoglobin determination, along with serology for syphilis if it is prevalent in the population, is repeated at 28 to 32 weeks (Hollier, 2003; Kiss, 2004). For women at increased risk for HIV acquisition during pregnancy, repeat testing is recommended in the third trimester, preferably before 36 weeks (American College of Obstetricians and Gynecologists, 20 16). Similarly, women who engage in behaviors that place them at high risk for hepatitis B virus infection are retested at the time of hospitalization for delivery. Women who are D (h) negative and are unsensitized should have an antibody screening test repeated at 28 to 29 weeks, and anti-D immunoglobulin is given if they remain unsensitized (Chap. 15, p. 305).
he CDC (20e1e0b) recommends that vaginal and rectal group B streptococcal (GBS) cultures be obtained in all women between 35 and 37 weeks' gestation, and the American College of Obstetricians and Gynecologists (20e1e6g) has endorsed this recommendation. Intrapartum antimicrobial prophylaxis is provided to those whose culture results are positive. Women with GBS bacteriuria or a previous infant with invasive disease are given empirical intrapartum prophylaxis. Trials are in progress to test an investigational vaccine (Donders, 2016; Schrag, 2016). hese infections are described further in Chapter 64 (p. 1220).
All pregnant women are screened for gestational diabetes mellitus, whether by history, clinical factors, or routine laboratory testing. Although laboratory testing between 24 and 28 weeks' gestation is the most sensitive approach, there may be pregnant women at low risk who are less likely to beneit from testing (American College of Obstetricians and Gynecologists, 2017c). Gestational diabetes is discussed in Chapter 57 (p. 11 07).