[1] Univ Calif Los Angeles, David Geffen Sch Med, Dept Family Med, Los Angeles, CA 90024 USA
[2] Univ Calif Los Angeles, Sch Publ Hlth, Dept Community Hlth Sci, Los Angeles, CA 90095 USA
[3] Univ Calif Los Angeles, David Geffen Sch Med, Dept Obstet & Gynecol, Los Angeles, CA 90095 USA
[4] Univ Calif Los Angeles, Sch Nursing, Los Angeles, CA 90095 USA
[5] Univ Calif Los Angeles, Sch Publ Hlth, Dept Hlth Serv, Los Angeles, CA 90095 USA
[6] Univ Michigan, Sch Med, Dept Epidemiol, Ann Arbor, MI 48109 USA