The prevalence of both obesity and gestational diabetes mellitus (GDM) have increased, andh is associated with adverse perinatal outcomes including fetal overgrowth, neonatalbidity, hypertensive disorders of pregnancy, and cesarean delivery. Women with GDM who areverweight and obese have higher rates of pregnancy complications when compared toweight women with GDM, which may occur in part due to suboptimal glycemic control. Theurrent recommendations for glycemic targets in pregnant women with diabetes are notgorously defined, and they far exceed the mean fasting (70.9 ±7.8 mg/dL) and 1 hour postprandial (108.9 ± 12.9 mg/dL) glucose values in pregnant women without GDM. Our prior work demonstrated that use of intensive (fasting <90, 1 hr post-prandial <120 mg/dL) compared todard (fasting <95 mg/dL, 1 hr post-prandial <140 mg/dL) glycemic targets resulted inved glycemic control without increasing the risk for hypoglycemia. The Intensive Glycemic Targets in Overweight and Obese Women with Gestational Diabetes Mellitus: Aulticenter Randomized Trial (iGDM Trial) is a large, pragmatic randomized clinical trial designed to investigate the impact of intensive versus standard glycemic targets on perinatalutcomes in women with GDM who are overweight and obese. During the 5-year project period, aultidisciplinary team of investigators from 4 medical centers representing regions of the.S. with high rates of obesity will randomize 828 overweight and obese women with GDM toher intensive or standard glycemic targets. The specific aims of this project are: 1) Determine the effectiveness of intensive glycemic targets in reducing the risk for neonatalbidity and large for gestational age birthweight in overweight and obese women with GDM, 2) Assess the safety of intensive glycemic targets as measured by the frequency ofhypoglycemia in overweight and obese women with GDM, and 3) Evaluate theveness of intensive glycemic control compared with standard glycemic control asured by the incremental cost per case of neonatal morbidity and LGA birth weightvented and per Quality-adjusted Life-year. The expected outcome of this study is high-quality evidence on the effectiveness, safety, and cost-effectiveness of intensive glycemic targets in reducing adverse perinatal outcomes among overweight and obese women with GDM. If proven effective, use of intensive glycemic targets in overweight and obese women with GDM will have an important positive impact on the health of these high risk women andheir infants.