Objective: To evaluate whether one-step gestational diabetes screening recommended by The International Association of the Diabetes and Pregnancy Study Groups (IADPSG) is associated with better maternal, perinatal, or neonatal outcomes than the two-step Carpenter-Coustan screening.
Methods: In this before-after retrospective cohort study conducted between July 1, 2010, and December 31, 2013, we compared Carpenter-Coustan and IADPSG screening in patients with singleton pregnancies. All patients diagnosed with gestational diabetes received intensive teaching, home glucose monitoring, and medications as indicated. The primary outcome was the rate of large-for-gestational-age neonates. Secondary outcome measures were macrosomia (greater than 4,000 g), primary cesarean delivery, neonatal intensive care unit admission, preterm delivery, preeclampsia, and hyperbilirubinemia. We determined that a sample size of 2,782 per group was sufficient to detect a 2% difference in the primary outcome between groups with 80% power assuming a 10% incidence in the before group. The groups were compared using Fisher exact test for proportions and a χ test for odds ratios.
Results: In the before (Carpenter-Coustan) group, 513 (17%) of the 2,972 patients were diagnosed with gestational diabetes, and in the after (IADPSG) group, 847 (27%) of the 3,094 patients were so diagnosed (P<.001). There was no significant difference in rates of large for gestational age, 10% and 9%, respectively (P=.25). The IADPSG group had a significantly higher primary cesarean delivery rate-16% compared with 20% (P<.001), but there were no significant differences in any other pregnancy outcomes.
Conclusion: Although one-step screening was associated with more patients being treated for gestational diabetes, it was not associated with a decrease in large-for-gestational-age or macrosomic neonates but was associated with an increased rate of primary cesarean delivery. Our results did not support the IADPSG-recommended screening protocol.