[1] George Washington Univ, Ctr Biostat, Washington, DC 20052 USA
[2] Northwestern Univ, Dept Obstet, Chicago, IL 60611 USA
[3] Northwestern Univ, Dept Gynecol, Chicago, IL 60611 USA
[4] Ohio State Univ, Columbus, OH 43210 USA
[5] Univ Alabama Birmingham, Birmingham, AL USA
[6] Univ Texas SW Med Ctr Dallas, Dallas, TX 75390 USA
[7] Univ Utah, Salt Lake City, UT USA
[8] Wake Forest Univ Hlth Sci, Winston Salem, NC USA
[9] Wayne State Univ, Detroit, MI USA
[10] Brown Univ, Providence, RI 02912 USA
[11] Univ Miami, Miami, FL USA
[12] Univ Tennessee, Memphis, TN USA
[13] Univ N Carolina, Chapel Hill, NC USA
[14] Univ Texas Hlth Sci Ctr Houston, Houston, TX USA
[15] Case Western Reserve Univ, Metrohlth Med Ctr, Cleveland, OH USA
[16] Eunice Kennedy Shriver Natl Inst Child Hlth & Hum, Bethesda, MD USA
[17] Univ Pittsburgh, Pittsburgh, PA USA