[1] Univ Penn, Sch Med, Dept Genet, Ctr Res Reprod & Womens Hlth, Philadelphia, PA 19104 USA
[2] Univ Penn, Sch Med, Dept Obstet & Gynecol, Philadelphia, PA 19104 USA
[3] Northwestern Univ, Sch Med, Div Endocrinol Metab & Mol Med, Chicago, IL 60611 USA
[4] Penn State Univ, Dept Obstet & Gynecol, Hershey, PA 17033 USA