1. Epidemiology and Applied Research Branch, Division of Cancer Prevention and Control, Centers for Disease Control and Prevention, Atlanta, Georgia
2. Reproductive Statistics Branch, National Center for Health Statistics, Division of Vital Statistics, Centers for Disease Control and Prevention, Hyattsville, Maryland
3. Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California, San Francisco
4. Center for Healthcare Value, University of California, San Francisco