Women with previous gestational diabetes mellitus (GDM) display a range of metabolic abnormalities. To characterize maternal metabolic profiles during the first year postpartum and to determine the relative contribution of race, women with recent GDM underwent a complete metabolic characterization 6-12 weeks after delivery (early) and 1 year (late) postpartum. From April 2009-April 2012, we prospectively evaluated 214 prior GDM women (pGDM; 168 Caucasian (W) and 46 African-American (NW)). Anthropometric measurements (weight, height, body mass index (BMI), waist circumference (WC), body fat distribution (waist/hip (W/H) and waist/height (WHt) ratio), blood pressure (BP) and blood specimens were obtained. Insulin and glucose concentrations at baseline, 30, 60, and 120 min during a 2-h 75-g oral glucose tolerance test (OGTT) were used to derive fasting and glucose-stimulated insulin sensitivity and insulin secretion indices. Fasting and mean blood glucose (FBG, MBG), total cholesterol (C), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and triglycerides (TRG) were determined. The study cohort included 105 pGDM women (85 W, 20 NW) studied early and late postpartum. Seventy-nine pGDM women did not complete repeat testing and 30 women on medications for early postpartum dysglycemia were excluded from the analyses. At 1-year follow-up, dysglycemia was more prevalent in NW women with 50% having impaired glucose regulation compared to 25.9% of W women. NW pGDM women had lower insulin sensitivity and reduced β-cell function compared with W pGDM counterparts. Postpartum weight and WC gain, BP and MBG were also significantly greater in NW pGDM women. A less favorable lipid profile (higher LDL-C and TRG) was observed in W pGDM women. Weight gain, particularly increased central adiposity after delivery, and lower breastfeeding rates were strongly associated with deterioration of β-cell compensation for insulin resistance which is a key factor in the greater prevalence of glycemic impairment in NW pGDM women. The study was registered at http://www.clinicaltrials.gov (NCT00849849).