Vanlalhruaii, et al. - This retrospective study was designed to evaluate the effect of metformin on maternal and fetal outcomes when initiated within the first trimester of pregnancy in Gestational Diabetes mellitus (GDM). No significant adverse maternal or fetal outcomes were observed with the initiation of metformin within the first trimester of pregnancy. However, among women who were exposed to metformin in early pregnancy, vigilance for premature births was recommended.