© 2019 Elsevier Inc. Background: Although in 2013 the American College of Obstetricians and Gynecologists recommended early screening for gestational diabetes in obese women, no studies demonstrate an improvement in perinatal outcomes with this strategy. Objective: We sought to determine whether early screening for gestational diabetes improves perinatal outcomes in obese women. Materials and Methods: Randomized controlled trial comparing early gestational diabetes screening (14−20 weeks) to routine screening (24−28 weeks) in obese women (body mass index ≥30 kg/m2) at 2 tertiary care centers in the United States. Screening was performed using a 50-g, 1-hour glucose challenge test followed by a 100-g, 3-hour glucose tolerance test if the initial screen was ≥135 mg/dL. Gestational diabetes was diagnosed using Carpenter−Coustan criteria. Women not diagnosed at 14 to 20 weeks were rescreened at 24 to 28 weeks. Exclusion criteria were pre-existing diabetes, major medical illness, bariatric surgery, and prior cesarean delivery. The primary outcome was a composite of macrosomia (>4000 g), primary cesarean delivery, hypertensive disease of pregnancy, shoulder dystocia, neonatal hyperbilirubinemia, and neonatal hypoglycemia (assessed within 48 hours of birth). Results: A total of 962 women were randomized, and outcomes were available for 922. Of these 922 women, 459 (49.8%) were assigned to early screen and 463 (50.2%) to routine screen. Baseline characteristics were balanced between groups. In the early screening group, 69 (15.0%; 95% confidence interval, 11.9−18.6%) were diagnosed with gestational diabetes: 29 (6.3%; 95% confidence interval, 4.3−8.9%) at <20 weeks and 40 (8.7%; 95% confidence interval, 6.3−11.7%) at >24 weeks. Of those randomized to routine screening, 56 (12.1%; 95% confidence interval, 9.3−15.4%) had gestational diabetes. Early screening did not reduce the incidence of the primary outcome (56.9% in the early screen versus 50.8% in the routine screen, P =.07; relative risk, 1.12; 95% confidence interval, 0.99−1.26). Conclusion: Early screening for gestational diabetes in obese women did not reduce the composite perinatal outcome.