1. Department of Family Health Care Nursing, School of Nursing, University of California, San Francisco, California.
2. Division of Epidemiology and Community Health, School of Public Health, University of Minnesota.
3. Departments Epidemiology & Biostatistics and Obstetrics, Gynecology, & Reproductive Sciences, University of California, San Francisco.
4. Departments of Human Anatomy and Obstetrics and Gynecology, University of Nairobi, Nairobi, Kenya.
5. Department of Sociology, Woodrow Wilson School of Public and International Affairs, and Office of Population Research, Princeton University, Princeton, New Jersey.