[1] Columbia Univ, Coll Phys & Surg, Dept Obstet & Gynecol, New York, NY 10032 USA
[2] Duke Univ, Sch Med, Dept Obstet & Gynecol, Durham, NC USA
[3] Yale Univ, Sch Med, Dept Obstet & Gynecol, New Haven, CT 06510 USA
[4] Univ Texas Southwestern Med Sch, Dept Obstet & Gynecol, Dallas, TX USA
[5] Univ Calif Irvine, Sch Med, Dept Obstet & Gynecol, Irvine, CA 92717 USA
[6] Univ Texas Houston, Sch Med, Dept Obstet Gynecol & Reprod Sci, Houston, TX USA
[7] Northwestern Univ, Feinberg Sch Med, Dept Obstet & Gynecol, Chicago, IL 60611 USA
[8] Univ Texas Med Branch, Sch Med, Dept Obstet Gynecol, Galveston, TX 77555 USA
[9] Univ Texas Med Branch, Sch Med, Dept Anesthesiol, Galveston, TX 77555 USA
[10] Univ Alabama Birmingham, Sch Med, Dept Obstet & Gynecol, Birmingham, AL USA
[11] High Risk Pregnancy Ctr, Las Vegas, NV USA
[12] Washington Univ, Sch Med, Dept Obstet & Gynecol, St Louis, MO 63110 USA
[13] Univ Mississippi, Sch Med, Dept Obstet & Gynecol, Jackson, MS USA
[14] Baylor Coll Med, Dept Obstet & Gynecol, Houston, TX 77030 USA
[15] Univ N Carolina, Sch Med, Dept Obstet & Gynecol, Chapel Hill, NC USA
[16] Soc Maternal Fetal Med, Washington, DC USA
[17] Harvard Univ, Sch Med, Dept Obstet & Gynecol, Boston, MA USA
[18] Eunice Kennedy Shriver Natl Inst Child Hlth & Hum, Bethesda, MD USA