What is the recommended prenatal screening for gestational diabetes?

Gestational Diabetes Mellitus (GDM) screening: standard one-step or two-step approach. Two-step (US standard): (1) Glucose Challenge Test (GCT) at 24-28 weeks: drink 50g glucose, check blood glucose 1 hour later; cutoff typically 130-140 mg/dL; if abnormal, proceed to confirmatory test; (2) 3-hour Glucose Tolerance Test (GTT): fasting; drink 100g glucose; check at 1, 2, 3 hours; GDM diagnosed if 2+ values exceed cutoffs (fasting 95, 1hr 180, 2hr 155, 3hr 140 mg/dL by Carpenter-Coustan criteria). Earlier screening (first trimester) for high-risk women: prior GDM, BMI ≥30, family history of T2DM, prior macrosomic baby, ethnic background with high T2DM rates (Hispanic, Black, Native American, Asian, Pacific Islander). Risks of untreated GDM: macrosomia (>4kg) with shoulder dystocia and birth trauma; neonatal hypoglycemia; respiratory distress; long-term: child increased obesity and diabetes risk; mother increased risk of T2DM (50% within 10 years). Management: nutrition therapy (consult dietitian, carb counting), exercise (after physician clearance), self-monitoring (4-7 times daily), insulin if diet/exercise inadequate (oral hypoglycemics increasingly used). Postpartum: 75g 2-hour OGTT at 6-12 weeks to identify those with persistent diabetes.