Using the 100-g oral glucose tolerance test to predict fetal and maternal outcomes in women with gestational diabetes mellitus

Background: This 5-year cohort study investigated gestational diabetes mellitus (GDM) using new diagnostic criteria and predictive factors for maternal and fetal outcomes. Methods: From March 2001 to February 2006, 8557 pregnant women underwent a 50-g glucose challenge test (GCT) at 24 to 28 weeks of gestation. A diagnosis of GDM was based on a a one-hour plasma glucose level ≧ 140 mg/dl on the 50 g GCT, followed by at lease two abnormal values on a 100-g oral glucose tolerance test (OGTT), according to the Carpenter and Coustan modification of the National Diabetes Data Group (NDDG) criteria. Maternal and fetal outcomes were compared with women with normal glucose tolerance (NGT). Results: The incidence of GDM was 7.4%. After excluding women with twin pregnancies, 617 women with GDM and 1250 women with NGT were enrolled for comparison. Older age (33.7 ± 4.1 vs. 32.2 ± 4.1, p < 0.001), lower weight gain during pregnancy (13.2 ± 4.4 vs. 14.6 ± 4.0 kg, p < 0.001), and higher rates of caesarean section (43.8% vs. 32.7%, p < 0.001) occurred in women with GDM compared to those in the NGT group. The rates of macrosomia and neonatal death were higher in the GDM group than the NGT group (7.0% vs. 1.9%, p < 0.001 and 0.6% vs. 0.0%, p = 0.005 respectively). The fasting glucose on the 100-g OGTT was positively correlated with birth weight in the GDM group (r = 0.117, 95% CI 0.038-0.194, p = 0.004). A value exceeding 90 mg/dl was 80% sensitive and 50% specific for macrosomia. Conclusions: The incidence of GDM in Taiwan is increasing more than before based on current diagnostic criteria. The fasting glucose on the 100-g OGTT correlates closely with birth weight and is also an independent risk factor for macrosomia. Focusing on women with fasting blood glucose concentrations > 90 mg/dL is anticipated to improve outcomes effectively.