1. Department of Population, Family and Reproductive Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland.
2. Bureau of Family Health and Nutrition, Massachusetts Department of Public Health, Boston, Massachusetts.
3. Division of Reproductive Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia.
4. Department of Gynecology and Obstetrics, Johns Hopkins School of Medicine, Baltimore, Maryland.