Is early diagnosis and treatment of mothers at high risk for gestational diabetes beneficial for mothers or neonates?
This well-designed randomized controlled trial showed modest benefits of screening pregnant patients at high risk for GDM in early pregnancy and treating if positive. A composite adverse neonatal outcome was reduced in the early treatment group (NNT=18). Severe maternal perineal injury was also reduced in the early treatment group (NNT= 36).
Randomized controlled trial (single-blinded)
This report is of an international multisite randomized controlled trial of early (before 20 weeks' gestation) gestational diabetes (GDM). The study included pregnant patients between 4 weeks' to 19 weeks 6 days' gestation with one or more risk factors for GDM, including previous diagnosis of GDM, body mass index greater than 30, age at least 40 years, first-degree relative with diabetes, previous macrosomia, polycystic ovarian syndrome, or non-European ancestry. Women 18 years and older were eligible if a 75-mg 2-hour oral glucose tolerance test (OGTT) performed before 20 weeks' gestation showed any of the following: fasting glucose 92 to 109, 1-hour glucose greater than 180, or 2-hour glucose 153 to 199. Participants were randomized to receive immediate treatment (n = 406) or repeat OGTT at 24 to 28 weeks (n = 396; control patients). Among control patients, 67% met the diagnostic criteria described for GDM and were treated at that time. Management for GDM included education, dietary advice, instruction on how to monitor blood glucose, and standard pharmacological treatment with metformin or insulin based on specific glycemic thresholds. The first primary outcome was a composite adverse neonatal outcome including: birth before 37 weeks' gestation, birth weight 4500 g or greater, birth trauma, neonatal respiratory distress during the first 24 hours after birth, phototherapy, stillbirth or neonatal death, or shoulder dystocia. An adverse neonatal outcome occurred in 24.9% of persons in the early treatment group and 30.5% in the control group (–5.6 percentage points; 95% CI –10.1 to –1.2; P = .02; adjusted relative risk 0.82; 0.68 - 0.98; number needed to treat [NNT] = 18). The primary maternal outcome was pregnancy-related hypertension, which did not differ between groups (10.6% vs 9.9%; NS). Patients with preexisting hypertension were excluded from that analysis. Of multiple secondary outcomes assessed for both mothers and neonates, only severe maternal perineal injury was significantly different between groups: 0.8% in the early treatment group and 3.6% in the control group (–2.8 percentage points; –4.1 to –1.5).
Linda Speer, MD
Professor and Chair, Department of Family Medicine
University of Toledo