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Am Fam Physician. 2023;108(6):online

Clinical Question

Are early diagnosis and treatment of gestational diabetes mellitus (GDM) in high-risk patients beneficial for neonatal and maternal outcomes?

Bottom Line

This well-designed randomized controlled trial showed that screening pregnant patients at high risk for GDM in early pregnancy, and treating if positive, had modest benefits. A composite adverse neonatal outcome was reduced in the early treatment group (number needed to treat [NNT] = 18). Severe maternal perineal injury was also reduced in the early treatment group (NNT = 36). (Level of Evidence = 1b)


The study was an international, multisite randomized controlled trial of GDM in early pregnancy (i.e., before 20 weeks’ gestation). It included pregnant patients between four weeks’ and 19 6/7 weeks’ gestation with one or more risk factors for GDM, including a previous diagnosis of GDM, body mass index greater than 30 kg per m2, 40 years or older, a first-degree relative with diabetes, previous macrosomia, polycystic ovary syndrome, or non-European ancestry. Women 18 years and older were eligible for the study if a 75-mg, two-hour oral glucose tolerance test that was performed before 20 weeks’ gestation showed any of the following: a fasting glucose level of 92 to 109 mg per dL (5.11 to 6.05 nmol per L), one-hour glucose level greater than 180 mg per dL (9.99 nmol per L), or two-hour glucose level of 153 to 199 mg per dL (8.49 to 11.04 nmol per L). Participants were randomized to receive immediate treatment (n = 406) or repeat oral glucose tolerance test at 24 to 28 weeks’ gestation (n = 396 control patients). Among the control patients, 67% met the diagnostic criteria for GDM and were treated at that time. Management for GDM included education, dietary advice, instruction on how to monitor blood glucose, and standard pharmacologic 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 of 4,500 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 patients 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; 95% CI, 0.68 to 0.98; NNT = 18). The primary maternal outcome was pregnancy-related hypertension, which did not differ between groups (10.6% vs. 9.9%; not significant). Patients with preexisting hypertension were excluded from that analysis. Multiple secondary outcomes were assessed for mothers and neonates, and 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; 95% CI, −4.1 to −1.5).

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POEMs (patient-oriented evidence that matters) are provided by Essential Evidence Plus, a point-of-care clinical decision support system published by Wiley-Blackwell. For more information, see Copyright Wiley-Blackwell. Used with permission.

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