Goldenberg N, Glueck C. Minerva Ginecol. 2008 Feb;60(1):63-75.Links

Polycystic ovary syndrome (PCOS) is probably the most common endocrinopathy in women of childbearing age and is particularly common in African-American and Hispanic ethnic groups. It is characterized by oligo-amenorrhea, clinical and/or biochemical hyperandrogenism, polycystic ovaries, and, often, morbid obesity.

PCOS is associated with infertility and frequent 1st-trimester miscarriage, and with an increased risk of gestational diabetes. Insulin resistance with compensatory hyperinsulinemia plays an important role in the pathogenesis of PCOS.
Reduction of hyperinsulinemia with metformin-diet is associated not only with improvement of the biochemical endocrinopathy but, commonly, with the restoration of menstrual cycles and fertility. The combination of metformin and clomiphene citrate (CC) in CC-resistant patients provides additional benefit to a subset of patients, not responsive to metformin alone. Metformin appears to be safe for mothers and neonates (non-teratogenic) during pregnancy, though the results of double-blinded placebo-controlled studies are not yet available.

Benefits from metformin therapy during pregnancy include reduction of miscarriage, reduction in the likelihood of developing gestational diabetes, a reduction in fetal macrosomia, and prevention of excessive maternal weight gain during pregnancy. Rosiglitazone and pioglitazone are an effective therapy for ovulation induction, but pregnancy class C and should not be used during pregnancy.