INS and gestational diabetes: GDM not properly controlled with diet is commonly treated with insulin, although there are different guidelines: the American Diabetes association recommends using insulin as first-line treatment for GDM, the National Institute for Health and Care Excellence (NICE) proposes the use of metformin as first-line treatment, and the Society for Maternal Fetal Medicine considers metformin a reasonable and safe first-line pharmacologic alternative to insulin (57, 59, 60).