[1] Harvard Med Sch, Dept Obstet & Gynecol, Brigham & Womens Hosp, Boston, MA USA
[2] Harvard Med Sch, Dept Obstet & Gynecol, Massachusetts Gen Hosp, Boston, MA USA
[3] Univ Massachusetts, Dept Obstet & Gynecol, Univ Massachusetts Med Sch, Mem Med Ctr, Worcester, MA USA
[4] Harvard Med Sch, Dept Pediat, Massachusetts Gen Hosp, Boston, MA USA
[5] Harvard Med Sch, Dept Pathol, Massachusetts Gen Hosp, Boston, MA USA
[6] Weill Cornell Med, Dept Obstet & Gynecol, New York, NY USA