[1] Washington Univ, Sch Med, Dept Obstet & Gynecol, St Louis, MO 63110 USA
[2] Johns Hopkins Bloomberg Sch Publ Hlth, Dept Epidemiol, Baltimore, MD USA
[3] Maimonides Hosp, Dept Obstet & Gynecol, Brooklyn, NY 11219 USA
[4] Eunice Kennedy Shriver Natl Inst Child Hlth & Hum, Bethesda, MD USA
[5] Univ Calif San Francisco, Dept Pathol, San Francisco, CA 94140 USA
[6] Univ So Calif, Los Angeles, CA USA
[7] Montefiore Med Ctr, Dept Obstet & Gynecol, Bronx, NY 10467 USA
[8] Georgetown Univ, Dept Obstet & Gynecol, Washington, DC USA