Metformin Compared with Insulin in the Treatment of Pregnant Women with Overt Diabetes: A Randomized Controlled Trial

OBJECTIVE: To compare the safety and tolerability of metformin to insulin for glycemic control among women with preexisting type 2 and early A2 gestational diabetes. STUDY DESIGN: Women with preexisting type 2 diabetes and those diagnosed with gestational diabetes who required medical management prior to 20 weeks were randomly assigned to metformin or insulin. Glycemic control, defined as >50% capillary blood glucose within target range, was compared between groups. Other outcomes included patient tolerance, neonatal and obstetric complications, maternal weight gain, neonatal cord blood C-peptide, and patient satisfaction with therapy. RESULTS: Twenty-eight women completed the study, with 14 in each group. Of the 15 women assigned to metformin, 100% continued to receive metformin until delivery, although 43% required supplemental insulin to achieve glycemic control. Glucose measures did not differ between the groups, and the proportion who met fasting and postprandial glycemic target values did not differ between the groups. Women treated with metformin had significantly fewer subjective episodes of hypoglycemia compared with those using insulin (0% versus 36%; p = 0.04) as well as reported glucose values < 60 mg/dL (7.1% versus 50%; p = 0.03). CONCLUSION: Metformin should be considered for treatment of overt diabetes and early A2 gestational diabetes in pregnancy