[1] Univ Alabama Birmingham, Sch Med, Dept Med, Birmingham, AL 35233 USA
[2] Univ Alabama Birmingham, Sch Med, Dept Obstet & Gynecol, Birmingham, AL 35233 USA
[3] Geriat Res Educ & Clin Ctr, Dept Vet Affairs, Birmingham, AL USA
[4] Univ Utah, Ctr Hlth Sci, Dept Obstet & Gynecol, Salt Lake City, UT 84112 USA
[5] Loyola Univ, Med Ctr, Dept Obstet & Gynecol, Chicago, IL USA
[6] Johns Hopkins Sch Med, Dept Gynecol & Obstet, Baltimore, MD USA
[7] Univ Pittsburgh, Magee Womens Hosp, Pittsburgh, PA 15260 USA
[8] Univ Michigan, Sch Publ Hlth, Dept Biostat, Ann Arbor, MI USA
[9] NIH, NICHHD, Bethesda, MD USA