[1] Univ Pittsburgh, Dept Obstet, Pittsburgh, PA USA
[2] Univ Pittsburgh, Dept Gynecol, Pittsburgh, PA USA
[3] George Washington Univ, Ctr Biostat, Washington, DC USA
[4] Med Univ S Carolina, Charleston, SC 29425 USA
[5] Eunice Kennedy Shriver Natl Inst Child Hlth & Hum, Bethesda, MD USA
[6] Univ Chicago, Chicago, IL 60637 USA
[7] Univ Tennessee, Memphis, TN USA
[8] Ohio State Univ, Columbus, OH 43210 USA
[9] Univ Cincinnati, Cincinnati, OH USA
[10] Wayne State Univ, Detroit, MI USA