[1] Univ Pittsburgh, Sch Med, Dept Obstet Gynecol & Reprod Sci, 300 Halket St,Suite 2315, Pittsburgh, PA 15213 USA
[2] Magee Womens Res Inst, Dept Obstet Gynecol & Reprod Sci, Pittsburgh, PA USA
[3] Univ Pittsburgh, Grad Sch Publ Hlth, Dept Epidemiol, Pittsburgh, PA USA
[4] Univ Texas Hlth Sci Ctr Houston, Ctr Clin Translat Sci, Biostat Epidemiol Res Design Core, Houston, TX 77030 USA
[5] Univ Texas Houston, Div Epidemiol Human Genet & Environm Sci, Houston, TX USA