Serum screening for neural-tube defects is ofered at 15 to 20 weeks. Fetal aneuploidy screening may be performed at 11 to 14 weeks' gestation and/or at 15 to 20 weeks, depending on the protocol selected (Rink, 2016). Additionally, screening for certain genetic abnormalities is ofered to women at increased risk based on family history, ethnic or racial background, or age (American College of Obstetricians and Gynecologists, 20 17h). These are discussed in greater detail in Chapter 14 (p. 277). Some examples include testing for Tay-Sachs disease for persons of Eastern European Jewish or French Canadian ancestry; �-thalassemia for those of Mediterranean, Southeast Asian, Indian, Pakistani, or Mrican ancestry; a-thalassemia for individuals of Southeast Asian or Mrican ancestry; sickle-cell anemia for people of African, Mediterranean, Middle Eastern, Caribbean, Latin American, or Indian descent; and trisomy 21 for those with advanced maternal age.
In 2009, the Institute of Medicine and National Research Council revised guidelines for weight gain in pregnancy and continued to stratiy suggested weight gain ranges based on prepregnancy body mass index (BMI) (Table 9-4). The new guidelines included a specific, relatively narrow range of recommended weight gains for obese women. Also, the same recommendations apply to adolescents, short women, and women of
TABLE 9-4. Recommendations for Total and Rate of Weight Gain During Pregnancy
Underweight 28-40 1 (1l-1l.3) «1l8.5)
Normal weight 25-35 1 (0.8-1) (1l8.5-24.9)
Overweight 15-25 0.6 (0.5-0.7) (25.0-29.9)
Obese (::30.0) 11l-20 0.5 (0.4-0.6) aEmpirical recommendations for weight gain in twin pregnancies include: normal BMI, 37-54 Ib; overweight women, 31-50 Ib; and obese women, 25-42 lb. BMI = body mass index. Modified from the Institute of Medicine and National Research Council, 2009.
all racial and ethnic groups. The American College of Obstetricians and Gynecologists (2016i) has endorsed these measures.
When the Institute of Medicine guidelines were formulated, concern focused on low-birthweight newborns, however, current emphasis is directed to the obesity epidemic (Catalano, 2007). This explains renewed interest in lower weight gains during pregnancy. Obesity is associated with significantly greater risks for gestational hypertension, preeclampsia, gestational diabetes, macrosomia, cesarean delivery, and other complications (Chap. 48, p. 939). he risk appears "dose related" to prenatal weight gain. In a population-based cohort of more than 120,000 obese pregnant women, those who gained <15 lb had the lowest rates of preeclampsia, large-for-gestational age neonates, and cesarean delivery (Kiel, 2007). Among 100,000 women with normal prepregnancy BMI, De Vader and colleagues (2007) found that those who gained <25 Ib during pregnancy had a lower risk for preeclampsia, failed induction, cephalopelvic disproportion, cesarean delivery, and large-for-gestational age neonates. his cohort, however, had an increased risk for smallfor-gestational age newborns. Lifestyle intervention during pregnancy can result in less weight gain (Sagedal, 2017).