Metformin compared with insulin in the management of gestational diabetes mellitus: a randomized clinical trial

To evaluate the effect of metformin and insulin in glycemic control and compare pregnancy outcome in women with gestational diabetes mellitus (GDM).

This randomized controlled trial was conducted in GDM women with singleton pregnancy and gestational age between 20 and 34 weeks who did not achieve glycemic control on diet were assigned randomly to receive either metformin (n=80) or insulin (n=80). The primary outcomes were maternal glycemic control and birth weight. The secondary outcomes were neonatal and obstetric complications.

Two groups were comparable regarding the maternal characteristics. Two groups were similar in mean FBS (P=0.68) and postprandial measurements (P=0.87) throughout GDM treatment. The neonates of metformin group had less rate of birth weight centile >90 than insulin group (RR: 0.5, 95% CI: 0.3-0.9, P=0.012). Maternal weight gain was reduced in the metformin group (P<0.001). Two groups were comparable according to neonatal and obstetric complications (P>0.05). In metformin group 14% of women needed to supplemental insulin to achieve euglycemia.

Metformin is an effective and safe alternative treatment to insulin for women with GDM. This study does not show significant risk of maternal or neonatal adverse outcome with the use of metformin.