FOR THE BRAZILIAN GESTATIONAL DIABETES STUDY GROUP OBJECTIVE — To evaluate American Diabetes Association (ADA) and World Health Orga-

nization (WHO) diagnostic criteria for gestational diabetes mellitus (GDM) against pregnancy outcomes. RESEARCH DESIGN AND METHODS — This cohort study consecutively enrolled Brazilian adult women attending general prenatal clinics. All women were requested to under-take a standardized 2-h 75-g oral glucose tolerance test (OGTT) between their estimated 24th and 28th gestational weeks and were then followed to delivery. New ADA criteria for GDM require two plasma glucose values $5.3 mmol/l (fasting), $10 mmol/l (1 h), and $8.6 mmol/l (2 h). WHO criteria require a plasma glucose $7.0 mmol/l (fasting) or $7.8 mmol/l (2 h). Individuals with hyperglycemia indicative of diabetes outside of pregnancy were excluded. RESULTS — Among the 4,977 women studied, 2.4 % (95 % CI 2.0–2.9) presented with GDM by ADA criteria and 7.2 % (6.5–7.9) by WHO criteria. After adjustment for the effects of age, obesity, and other risk factors, GDM by ADA criteria predicted an increased risk of macrosomia (RR 1.29, 95 % CI 0.73–2.18), preeclampsia (2.28, 1.22–4.16), and perinatal death (3.10, 1.42–6.47). Similarly, GDM by WHO criteria predicted increased risk for macrosomia (1.45, 1.06–1.95), preeclampsia (1.94, 1.22–3.03), and perinatal death (1.59, 0.86–2.90). Of wome