Is Metformin an Alternative to Insulin for Indian Women with Gestational Diabetes Mellitus? Efficacy in Improving Glycemic Control and Perinatal Outcomes: A Randomized Controlled Trial

BACKGROUND: Metformin is an equally potent oral hypoglycemic agent in controlling blood sugars with more benefits compared to insulin. Metformin does not cause hypoglycemia and weight gain, it does not need special storage and it is easily administered. Also it is cost effective in low resource settings. It is less often preferred to insulin considering its efficacy and safety in pregnancy. Hence this study compares the efficacy of metformin and insulin and also evaluates the maternal and fetal outcomes in gestational diabetes mellitus. MATERIALS AND METHODS: 100 antenatal women with gestational age more than 12 weeks, diagnosed with GDM using ADA criteria with 75g OGTT were recruited in the study. Those cases whose sugars were not controlled with the trial of medical nutritional therapy for 2 weeks were started on either metformin or insulin by randomization. Fasting and 2 hours postprandial blood sugars were checked every week in both groups. In metformin group, if glycemic control was not achieved patient was switched over to insulin therapy. RESULTS: Glycemic control achieved in both groups were almost same except mean PPBS at 20 to 28 weeks. The mean FBS and mean PPBS in metformin and insulin group during 12-20, 20-28, 28-36 and 36-40 weeks were similar. The glycemic control in terms of mean PPBS at 20-28weeks was better in metformin group compared to insulin group. 16% of the GDM mothers in metformin group failed to achieve glycemic control and switched over to insulin. 22% of the GDM mothers in metformin group had gastrointestinal disturbance. There was no episode of maternal hypoglycemia in metformin group. 12% of GDM mothers in insulin group had maternal hypoglycemia. There was no significant difference in the maternal outcomes (pre-eclampsia, preterm labour, PROM, PPROM, oligohydramnios, polyhydramnios, UTI, candidiasis) and fetal outcomes (mean birth weight, incidence of LGA/SGA, APGAR scores in neonates). There was no significant difference in terms of mode of delivery, NICU admissions and neonatal complications (respiratory distress syndrome, neonatal hypoglycemia, hyper bilirubinemia, asphyxia, sepsis) between two groups. CONCLUSION: Glycemic control achieved with metformin and insulin in GDM were comparable. There was no significant difference in maternal outcomes, fetal outcomes, mode of delivery and neonatal complications between metformin and insulin groups. The advantage of metformin was, it did not cause maternal hypoglycemia. The adverse effect noted in metformin group was GI disturbance. Hence metformin proves to be a safe, effective and cheap alternative to insulin in the management of GDM