[1] Ohio State Univ, Coll Med, Dept Obstet & Gynecol, Columbus, OH 43210 USA
[2] George Washington Univ, Biostat Ctr, Washington, DC USA
[3] Univ Utah, Hlth Sci Ctr, Dept Obstet & Gynecol, Salt Lake City, UT USA
[4] Univ Texas SW Med Ctr Dallas, Dept Obstet & Gynecol, Dallas, TX 75390 USA
[5] Eunice Kennedy Shriver Natl Inst Child Hlth & Hum, Bethesda, MD USA
[6] Columbia Univ, Dept Obstet & Gynecol, New York, NY USA
[7] Brown Univ, Dept Obstet & Gynecol, Providence, RI 02912 USA
[8] Univ Alabama Birmingham, Dept Obstet & Gynecol, Birmingham, AL 35294 USA
[9] Univ N Carolina, Dept Obstet & Gynecol, Chapel Hill, NC USA
[10] Case Western Reserve Univ, Dept Obstet & Gynecol, MetroHlth Med Ctr, Cleveland, OH 44106 USA
[11] Univ Texas Med Branch, Dept Obstet & Gynecol, Galveston, TX 77555 USA
[12] Northwestern Univ, Dept Obstet & Gynecol, Chicago, IL 60611 USA
[13] Univ Texas Houston, Hlth Sci Ctr, Childrens Mem Hermann Hosp, Dept Obstet & Gynecol, Houston, TX USA
[14] Med Univ S Carolina, Dept Obstet & Gynecol, Charleston, SC 29425 USA