Compared with placebo in a study of individuals with gestational diabetes, early treatment with metformin did not meet a composite primary outcome. Because some prespecified secondary outcomes data indicated potential benefits of metformin, the authors conclude that the could be investigated further in larger clinical trials.
From June 2017 through Sept. 2022, participants with gestational diabetes were enrolled at a tertiary hospital and a smaller regional hospital in Ireland. The 535 pregnancies in 510 individuals were randomized to placebo or metformin (doses up to 2500 mg daily) in addition to usual care and followed until 12 weeks’ postpartum.
Based on a primary outcome of a composite of insulin initiation or a fasting glucose level of 5.1 mmol/L or greater at gestation weeks 32 or 38, the study showed the following: “Among 510 participants (mean age, 34.3 years), 535 pregnancies were randomized. The primary composite outcome was not significantly different between groups and occurred in 150 pregnancies (56.8%) in the metformin group and 167 pregnancies (63.7%) in the placebo group (between-group difference, −6.9% [95% CI, −15.1% to 1.4%]; relative risk, 0.89 [95% CI, 0.78-1.02]; P = .13). Of 6 prespecified secondary maternal outcomes, 3 favored the metformin group, including time to insulin initiation, self-reported capillary glycemic control, and gestational weight gain. Secondary neonatal outcomes differed by group, with smaller neonates (lower mean birth weights, a lower proportion weighing >4 kg, a lower proportion in the >90% percentile, and smaller crown-heel length) in the metformin group without differences in neonatal intensive care needs, respiratory distress requiring respiratory support, jaundice requiring phototherapy, major congenital anomalies, neonatal hypoglycemia, or proportion with 5-minute Apgar scores less than 7.”