One-Step Versus Two-Step Screening for Gestational Diabetes Mellitus

Abstract

Introduction: Gestational diabetes mellitus (GDM) screening remains controversial: one-step 75g OGTT (IADPSG) versus two-step (50g glucose challenge test followed by 100g OGTT, Carpenter-Coustan criteria). Methods: Systematic review of 10 RCTs and 12 cohort studies (n=78,902). Primary outcomes: GDM diagnosis rate, large-for-gestational-age (LGA), preeclampsia, cesarean delivery, neonatal hypoglycemia. Results: One-step increased GDM diagnosis from 6.2% to 15.3% (RR 2.47, p<0.001). However, no significant reduction in LGA (OR 0.93, p=0.21), preeclampsia (OR 0.90, p=0.34), or cesarean (OR 0.97, p=0.56). Neonatal hypoglycemia was slightly reduced (OR 0.84, p=0.04). Treatment burden increased (dietary counseling, glucose monitoring) without clear perinatal benefit. Discussion: The "one-step" diagnosis labels more women as GDM but most are mild. Treatment of mild GDM has marginal benefits. Conclusion: Two-step screening avoids overdiagnosis without compromising major perinatal outcomes. One-step is not superior.