[1] Duke Univ, Dept Obstet & Gynecol, Med Ctr, Durham, NC 27707 USA
[2] RTI Int, Res Triangle Pk, NC USA
[3] Loyola Univ, Stritch Sch Med, Dept Obstet & Gynecol, Chicago, IL 60611 USA
[4] Loyola Univ, Stritch Sch Med, Dept Urol, Chicago, IL 60611 USA
[5] Univ Alabama Birmingham, Dept Obstet & Gynecol, Birmingham, AL USA
[6] Univ Utah, Dept Obstet & Gynecol, Salt Lake City, UT USA
[7] Cleveland Clin, Dept Obstet & Gynecol, Cleveland, OH USA
[8] Kaiser Permanente San Diego, Dept Obstet & Gynecol, San Diego, CA USA
[9] Univ Texas SW Med Ctr Dallas, Dept Obstet & Gynecol, Dallas, TX 75390 USA
[10] Univ Pittsburgh, Pittsburgh, PA USA
[11] Oakwood Hosp & Med Ctr, Dearborn, MI USA
[12] Oakland Univ, William Beaumont Sch Med, Dept Urol, Beaumont Hlth Syst, Royal Oak, MI USA
[13] Univ Michigan, Dept Biostat, Ann Arbor, MI 48109 USA
[14] Eunice Kennedy Shriver Natl Inst Child Hlth & Hum, Contracept & Reprod Hlth Branch, Populat Res Ctr, NIH, Rockville, MD USA