[1] RTI Int, Biostat & Epidemiol Div, Res Triangle Pk, NC USA
[2] Eunice Kennedy Shriver Natl Inst Child Hlth & Hum, Bethesda, MD 20892 USA
[3] Northwestern Univ, Dept Obstet, Chicago, IL 60611 USA
[4] Northwestern Univ, Dept Gynecol, Chicago, IL 60611 USA
[5] Univ Calif Irvine, Irvine, CA USA
[6] Univ Utah, Hlth Sci Ctr, Salt Lake City, UT USA
[7] Columbia Univ, New York, NY USA
[8] Univ Pittsburgh, Pittsburgh, PA USA
[9] Univ Penn, Philadelphia, PA 19104 USA
[10] Case Western Reserve Univ, MetroHlth Med Ctr, Cleveland, OH 44106 USA
[11] Indiana Univ, Indianapolis, IN 46204 USA
[12] Univ Texas Med Branch, Galveston, TX 77555 USA