Metformin
Widely used for gestational diabetes mellitus (GDM) and type 2 diabetes in pregnancy. Crosses the placenta, with fetal concentrations approximating maternal concentrations. Despite this, no teratogenicity has been demonstrated in large human studies. Long-term follow-up data (MiG TOFU trial) showed increased childhood adiposity in metformin-exposed offspring; clinical significance is uncertain. Many clinicians use it as adjunct or alternative to insulin for GDM.
