Many women come into pregnancy with diabetes that is controlled with either Metformin or diet control; however, the current standard of care for the treatment of preexisting diabetes in pregnancy is insulin. Metformin is widely used in the non-pregnant population for glycemic control, and has been used in pregnancy for other indications without adverse maternal or fetal outcomes. What remains unproven is the ability of Metformin to adequately control glucose in women during pregnancy.