Early Screening for Gestational Diabetes Mellitus and Pregnancy Outcomes: A Systematic Review.

Gestational diabetes mellitus is typically diagnosed between 24 and 28 weeks of pregnancy. However, early screening (≤20 weeks) is increasingly promoted for high-risk women despite uncertain clinical benefits. We systematically reviewed randomized controlled trials (January 2000-March 2025) comparing early (≤ 20 weeks) versus standard (24-28 weeks) screening in women without pre-existing type 1 or type 2 diabetes. We searched MEDLINE, Embase, Cochrane Central Register of Controlled Trials, Web of Science, Scopus, CINAHL, and ClinicalTrials.gov. Out of 4,216 records, three trials comprising 2,540 women were included. Two trials enrolled women with obesity, and the third included a broader high-risk cohort. Early screening identified more cases of gestational diabetes (15.0% vs 12.0%) but offered no clinical advantage. In two trials using the same neonatal composite, adverse events were comparable (53.7% vs 48.6%). Similarly, rates of birthweight > 4,000 g, pregnancy-related hypertension (17.9% vs 15.1%), and cesarean delivery (37.6% vs 35.5%) showed no benefit. Current evidence suggests that shifting testing to before 24 weeks does not improve maternal or neonatal outcomes and may lead to additional interventions without clear benefit. Larger pragmatic studies are needed to evaluate cost-effectiveness and determine whether targeted early screening in truly high-risk individuals can be justified.