Justiication for screening and treatment of women with gestational diabetes was strengthened by the study by Crowther and coworkers (2005). They assigned 1000 women with gestational diabetes between 24 and 34 weeks' gestation to receive dietary advice with blood glucose monitoring plus insulin therapy-the intervention group-or to undergo routine prenatal care. Women were diagnosed as having gestational diabetes if their blood glucose was > 100 mg/ dL ater an overnight fast and was between 140 and 198 mg/dL 2 hours ater ingesting a 75-g glucose solution. Women in the intervention group had a signiicantly lower risk of a composite adverse outcome that included perinatal death, shoulder dystocia, fetal bone fracture, and fetal nerve palsy. Macrosomia deined by birthweight ::4000 g complicated 10 percent of deliveries in the intervention group compared with 21 percent in the routine prenatal care group. Cesarean delivery rates were almost identical in the two study groups.
Slightly diferent results were reported by the MaternalFetal Medicine Units Network randomized trial of958 women (Landon, 2009). Dietary counseling plus glucose monitoring was compared with standard obstetrical care in women with mild gestational diabetes to reduce perinatal morbidity rates. Mild gestational diabetes was identiied in women with fasting glucose levels <95 mg/dL. hey reported no diferences in rates of composite morbidity that included stillbirth; neonatal hypoglycemia, hyperinsulinemia, and hyperbilirubinemia; and birth trauma. Importantly, secondary analyses demonstrated a 50-percent reduction in macrosomia, fewer cesarean deliveries, and a signiicant decrease in shoulder dystocia rate-1.5 versus 4 percent-in treated versus control women.
Based largely on these two landmark studies, the U.S. Preventive Sevices Task Force (2014) now recommends universal screening in low-risk women after 24 weeks' gestation. However, the Task Force concluded that evidence is insuicient to assess the balance of benefits versus harms of screening before 24 weeks. For screening, the optimal OGTT ro identiy gestational diabetes has not been agreed upon. The World Health Organization (2013) and the ADA (2017a) recommend the tions listed are met or exceeded for a positive diagnosis.
(Serum glucose level.
dSerum or plasma glucose level.
NDDG = National Diabetes Data Group.
Data from American Diabetes Association, 201n7a; Ferrara, 2002.
75-g, 2-hour OGTT, but acknowledge that the diagnosis can be accomplished using the two-step strategy. In the United States, however, the 1 OO-g, 3-hour OGTT performed after an overnight fast is recommended by the American College of Obstetricians and Gynecologists (2017a). Proposed criteria for interpretation of the diagnostic 100-g OGTT are shown in Table 57-13. In a secondary analysis of the Maternal-Fetal Medicine Units Network treatment trial, Harper and colleagues (2016) showed that women diagnosed with either the National Diabetes Data Group (NDDG) or the Carpenter-Co us tan criteria beneited from treatment. However, the number needed to treat to prevent a shoulder dystocia was higher for the Carpenter-Co us tan criteria. At Parkland Hospital we continue to use the NDDG criteria for diagnosis. Criteria for the 75-g OGTT recommended are shown in Table 57-11.
The Hyperglycemia and Adverse Pregnancy Outcome Study