[1] Yale Sch Med, Equ Res & Innovat Ctr, 100 Church St South,Suite A200, New Haven, CT 06519 USA
[2] Yale Sch Publ Hlth, Dept Chron Dis Epidemiol, New Haven, CT USA
[3] Yale Sch Med, Dept Obstet Gynecol & Reprod Sci, New Haven, CT 06519 USA
[4] Columbia Univ, Vagelos Coll Phys & Surg, Dept Obstet & Gynecol, New York, NY USA