[1] Univ Michigan, Dept Med, Ann Arbor, MI 48109 USA
[2] Univ Michigan, Dept Obstet & Gynecol, Ann Arbor, MI 48109 USA
[3] Univ Michigan, Dept Epidemiol, Ann Arbor, MI 48109 USA
[4] MedStar Hlth Res Inst, Hyattsville, MD 20782 USA
[5] Univ Miami, Dept Med, Miami, FL 33021 USA
[6] George Washington Univ, Biostat Ctr, Rockville, MD 20852 USA
[7] Univ Calif San Diego, Dept Family & Prevent Med, La Jolla, CA 92093 USA
[8] Univ Chicago, Dept Med, 5841 S Maryland Ave, Chicago, IL 60637 USA