Comparison of metformin and insulin therapy for the treatment of gestational diabetes mellitus—a randomised controlled trial

Background Insulin therapy though time-tested and effective option requires a certain degree of expertise (or training) and storage precautions. Metformin is cheap, orally taken, and does not cause hypoglycemia. Controversy exists regarding safety and efficacy of metformin therapy during pregnancy. Methods Newly diagnosed women with GDM as per IADPSG criteria requiring drug therapy were randomized to either metformin or insulin after informed consent. Each group has 80 to show 8 mg difference in blood sugar control. Maternal and fetal outcomes were noted and maternal satisfaction to therapy was assessed by pre-determined questionnaire. Comparison of continuous variables was done by Student t test and categorical variables by chi-square test. Results Control of blood sugar was achieved in 71% of Insulin group and 76% of metformin group and the difference is not statistically significant. Sixteen percent of women in metformin group needed insulin. No difference in maternal outcomes of hypertension, preterm labor, and cesarean section rate. Neonatal hypoglycemia occurred in 6.25% of insulin group and 1.25% of metformin group and 28% of new-borns of insulin group needed NICU care when compared to 11% of metformin group. Eighty percent of metformin group and 31% of insulin group opined to take metformin as initial drug of choice. Conclusion Metformin is as effective as insulin for control of blood sugar in women with GDM. Obese women and GDM diagnosed in first and second trimester may require addition of Insulin later. Most of the women preferred oral therapy with metformin initially and add insulin if needed.