Continuing metformin throughout pregnancy has been shown to also significantly reduce the incidence of insulin-requiring gestational diabetes as well as fetal-growth restriction. Metformin has been used as treatment for polycystic ovarian disease and has been reported to reduce the incidence of gestational diabetes in women who use the drug throughout pregnancy (Glueck and colleagues, 2004). Even so, it is usually recommended that metformin be discontinued once pregnancy is diagnosed because it is long known to reach the fetus (Harborne and associates, 2003). The Fifth International Workshop Conference recommended that metformin treatment for gestational diabetes be limited to clinical trials with long-term infant follow-up (Metzger and co-workers, 2007). Subsequently, Rowan and colleagues (2008) reported results of a study in which they randomized 751 women with gestational diabetes to metformin or insulin treatment. The primary outcome was a composite of one or more of neonatal hypoglycemia, respiratory distress, phototherapy, birth trauma, 5-minute Apgar score of 7 or less, and preterm birth. Similarities in the composite outcome between metformin and insulin led the investigators to conclude that metformin was not associated with increased perinatal complications.