[1] Northwestern Univ, Dept Prevent Med, Feinberg Sch Med, Chicago, IL 60201 USA
[2] RTI Int, Durham, NC USA
[3] NHLBI, Div Cardiovasc Sci, NIH, Bethesda, MD USA
[4] Indiana Univ, Sch Med, Dept Obstet & Gynecol, Indianapolis, IN 46202 USA
[5] Univ Utah, Sch Med, Dept Obstet & Gynecol, Salt Lake City, UT 84132 USA
[6] MetroHlth Syst, Dept Obstet & Gynecol, Cleveland, OH USA
[7] Hosp Univ Penn, Dept Obstet & Gynecol, Philadelphia, PA 19104 USA
[8] Yale Univ, Dept Obstet Gynecol & Reprod Sci, Sch Med, New Haven, CT USA
[9] Univ Texas Med Branch, Dept Obstet & Gynecol, Galveston, TX 77555 USA
[10] Univ Pittsburgh, Dept Obstet Gynecol & Reprod Sci, Magee Womens Res Inst, Sch Med, Pittsburgh, PA USA
[11] Columbia Univ, Dept Obstet & Gynecol, Irving Med Ctr, New York, NY USA
[12] Univ Calif Irvine, Dept Obstet & Gynecol, Sch Med, Orange, CA USA
[13] Northwestern Univ, Dept Obstet & Gynecol, Feinberg Sch Med, Chicago, IL USA