[1] Ohio State Univ, Coll Med, Dept Obstet & Gynecol, 395 West 12th Ave,Room 572, Columbus, OH 43210 USA
[2] George Washington Univ, Biostat Ctr, Washington, DC USA
[3] Univ Utah, Hlth Sci Ctr, Salt Lake City, UT USA
[4] Univ Texas Southwestern Med Ctr Dallas, Dept Obstet & Gynecol, Dallas, TX USA
[5] Eunice Kennedy Shriver Natl Inst Child Hlth & Hum, Dept Obstet & Gynecol, Bethesda, MD USA
[6] Columbia Univ, Dept Obstet & Gynecol, New York, NY USA
[7] Brown Univ, Dept Obstet & Gynecol, Providence, RI USA
[8] Univ Alabama Birmingham, Dept Obstet & Gynecol, Birmingham, AL 35294 USA
[9] Univ N Carolina, Dept Obstet & Gynecol, Chapel Hill, NC 27515 USA
[10] Case Western Reserve Univ, Dept Obstet & Gynecol, MetroHlth Med Ctr, Cleveland, OH 44106 USA
[11] Univ Texas Med Branch, Galveston, TX 77555 USA
[12] Northwestern Univ, Dept Obstet & Gynecol, Chicago, IL 60611 USA
[13] Univ Texas Hlth Sci Ctr Houston, Childrens Mem Hermann Hosp, Houston, TX 77030 USA
[14] Med Univ South Carolina, Dept Obstet & Gynecol, Charleston, SC 29425 USA
[15] Ohio State Univ, Columbus, OH 43210 USA
[16] Univ Utah, Hlth Sci Ctr, Salt Lake City, UT USA
[17] Univ Texas Southwestern Med Ctr Dallas, Dallas, TX 75390 USA
[18] Columbia Univ, New York, NY USA
[19] St Peters Univ Hosp, New Brunswick, NJ USA
[20] Christiana Care, Newark, DE USA
[21] Drexel Univ, Philadelphia, PA 19104 USA
[22] Brown Univ, Providence, RI 02912 USA
[23] Univ Alabama Birmingham, Birmingham, AL USA
[24] Univ N Carolina, Chapel Hill, NC 27515 USA
[25] Case Western Reserve Univ, MetroHlth Med Ctr, Cleveland, OH 44106 USA
[26] Univ Texas Med Branch, Galveston, TX 77555 USA
[27] Northwestern Univ, Evanston Hosp, NorthShore Hlth Syst, Chicago, IL 60611 USA
[28] Univ Texas Hlth Sci Ctr Houston, Childrens Mem Hermann Hosp, Houston, TX 77030 USA
[29] George Washington Univ, Biostat Ctr, Washington, DC USA
[30] Eunice Kennedy Shriver Natl Inst Child Hlth & Hum, Bethesda, MD USA