[1] Univ Wisconsin, Dept Obstet & Gynecol, Middleton, WI USA
[2] Univ Penn, Dept Obstet & Gynecol, Philadelphia, PA USA
[3] Univ Penn, Perelman Sch Med, Ctr Clin Epidemiol & Biostat, Dept Biostat Epidemiol & Informat, Philadelphia, PA USA
[4] Montefiores Inst Reprod Med & Hlth, Dept Obstet & Gynecol, Hartsdale, NY USA
[5] Univ Rochester, Dept Obstet & Gynecol, Rochester, NY USA
[6] Yale Sch Med, Dept Obstet & Gynecol, New Haven, CT USA
[7] Univ Penn, Perelman Sch Med, Dept Pediat, Philadelphia, PA USA