[1] Univ Calif San Francisco, Osher Ctr Integrat Hlth, UCSF Box 1726, San Francisco, CA 94143 USA
[2] Univ Calif San Francisco, Dept Psychiat & Behav Sci, San Francisco, CA 94143 USA
[3] Univ Calif San Francisco, Dept Obstetncs Gynecol & Reprod Sci, San Francisco, CA 94143 USA
[4] Univ Calif San Francisco, UCSF Calif Preterm Birth Initiat, San Francisco, CA 94143 USA
[5] Univ Calif San Diego, Dept Pediat, San Diego, CA USA
[6] Univ Iowa, Coll Publ Hlth, Dept Epidemiol, Iowa City, IA USA
[7] Univ Calif San Francisco, Dept Epidemiol & Biostat, San Francisco, CA 94143 USA
[8] Univ Calif San Francisco, Ctr Hlth & Community, San Francisco, CA 94143 USA