Procedures (methods): Pregnant women with T2DM between 10 weeks and 20 weeks 6 days and a singleton fetus will be randomized to insulin/placebo versus insulin/metformin. Primary outcome is composite adverse neonatal outcome (clinically relevant hypoglycemia, birth trauma, hyperbilirubinemia, stillbirth/neonatal death). Study visits monthly at clinical visits; blood draw at 24-30 weeks. Maternal and infant outcomes will be chart abstracted.