[1] Univ Alabama Birmingham, Dept Obstet & Gynecol, Birmingham, AL 35294 USA
[2] Univ Texas Med Branch, Dept Obstet & Gynecol, Galveston, TX USA
[3] Ohio State Univ, Dept Obstet & Gynecol, Med Ctr, Columbus, OH USA
[4] Thomas Jefferson Univ, Jefferson Med Coll, Dept Obstet & Gynecol, Philadelphia, PA USA
[5] Univ Texas Southwestern Med Ctr Dallas, Dept Obstet & Gynecol, Dallas, TX USA
[6] Columbia Univ, Coll Phys & Surg, Dept Obstet & Gynecol, New York, NY USA
[7] Univ Tennessee, Dept Obstet & Gynecol, Hlth Sci Ctr, Memphis, TN USA
[8] Univ Calif Irvine, Dept Obstet & Gynecol, Irvine, CA USA
[9] Northwestern Perinatal Ctr, Dept Obstet & Gynecol, Portland, OR USA
[10] Northshore Med Grp, Dept Obstet & Gynecol, Evanston, IL USA
[11] Univ Texas Houston, Med Sch Houston, Dept Obstet & Gynecol, Houston, TX USA
[12] St Peters Univ Hosp, Dept Obstet & Gynecol, New Brunswick, NJ USA
[13] USAF, Dept Obstet & Gynecol, Med Ctr, Wilford Hall, San Antonio, TX USA
[14] Univ Cincinnati, Dept Obstet & Gynecol, Cincinnati, OH USA
[15] Univ Oklahoma, Hlth Sci Ctr, Dept Obstet & Gynecol, Oklahoma City, OK USA
[16] Univ Alabama Birmingham, Dept Biostat, Birmingham, AL USA
[17] Norton Hlth Care, Louisville, KY USA