In patients with diet-controlled gestational diabetes, continuing pregnancy beyond 39 weeks was associated with increasing maternal and neonatal risks.
A retrospective cohort study published January 21, 2026, in Pregnancy found that continuing pregnancy beyond 39 weeks among patients with diet-controlled gestational diabetes mellitus (GDM) was associated with progressively higher maternal and neonatal risks, including cesarean delivery, shoulder dystocia, and large-for-gestational-age infants. The findings suggest that expectant management past 39 weeks can carry increasing risks for this population.1
Gestational diabetes mellitus affects an estimated 2% to 11% of pregnancies in the United States and up to 14% globally and is associated with higher rates of maternal and neonatal morbidity. Current guidance from the American College of Obstetricians and Gynecologists recommends delivery at 39 weeks for patients with medication-controlled GDM, while expectant management up to 41 weeks is considered acceptable for those whose glucose levels are controlled with diet alone, the authors noted.1,2
However, evidence comparing induction at 39 weeks with expectant management in diet-controlled GDM has been mixed, and no randomized trials have focused exclusively on this subgroup. As a result, stated the authors, optimal timing of delivery for these patients has remained uncertain.1
Investigators conducted a retrospective cohort study of singleton, live-born term deliveries at a single hospital between November 2010 and February 2024. The analysis focused on patients diagnosed with diet-controlled GDM who delivered at 39 weeks or later and excluded those with insulin-treated GDM, pregestational diabetes, multiple gestations, or other medical indications for early delivery.
All patients were managed under uniform institutional protocols, including standardized glucose screening, dietary counseling, and follow-up in a maternal-fetal medicine clinic. Patients with diet-controlled GDM were expectantly managed until 42 weeks unless other obstetric indications arose.
Of 156,214 total deliveries during the study period, 4467 occurred at 39 weeks or later among patients with diet-controlled GDM.
When outcomes at 41 weeks or later were compared with those at 39 weeks, advancing gestational age was associated with higher odds of several adverse maternal outcomes, even after adjustment for age and parity, including:
Neonatal outcomes followed a similar pattern, with higher risks observed among infants delivered at later gestational ages.
Adjusted odds ratios comparing delivery at 41 weeks or later versus 39 weeks showed:
When patients with diet-controlled GDM were compared with those without diabetes, rates of most adverse outcomes were higher overall in the GDM group. Importantly, the rate of increase with advancing gestational age was generally similar between groups, except for 2 outcomes where the effect was amplified in diet-controlled GDM:
“Patients with diet-controlled GDM are at increased risk of both maternal and neonatal morbidity when compared to a non-diabetic population,” the authors concluded, adding that risks increased with increasing gestational age. CD and LGA infants had an increased risk with increasing gestational age at a faster rate than those without diabetes.
“Delivery at 39–40 weeks for these patients may be associated with lower rates of primary CD and LGA infants but further prospective research is needed to truly define the optimal delivery timing for this population,” wrote the study investigators.
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