1 Department of Family & Community Medicine, University of California, San Francisco, CA 94110; Department of Obstetrics, Gynecology & Reproductive Sciences, University of California, San Francisco, CA 94110; Department of Epidemiology & Biostatistics, University of California, San Francisco, CA 94110. Electronic address: Christine.Dehlendorf@ucsf.edu.
2 Department of Family Medicine, Oregon Health and Science University, Portland, OR 97239.
3 Department of Obstetrics, Gynecology & Reproductive Sciences, University of California, San Francisco, CA 94110.