Can metformin replace insulin for gestational diabetes?

Contrary to conventional medical wisdom, metformin compares favorably with insulin for controlling blood sugar in A2 gestational diabetes-GD with elevated fasting blood sugar levels.

Researchers randomized women at less than 36 weeks' gestation to achieve normal blood sugar levels by either subcutaneous insulin injection (0.7 units) or 500 mg of metformin, with the goal of attaining postprandial blood glucose readings of less than 120 mg/dL and fasting blood sugars of between 60 and 90 mg/dL. Pregnant women were excluded from the study if they had conditions like insulin-dependent diabetes mellitus, chronic hypertension, or seizure disorders.

Thirty-one patients received insulin injection and 32 metformin. Those receiving the latter weighed about 30 lb more than the other group. Glucose levels were similar in each group and actually somewhat lower in the metformin group 2 hours after lunch (mean 106 vs. 112.5) and 2 hours after dinner (mean 108.1 vs. 109.2). There was little difference in abdominal delivery rates, shoulder dystocia, and postpartum hemorrhage and no differences in newborn statistics between the two groups, nor in birthweight, Apgar score at 5 minutes, or NICU admission.