1. Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California, San Francisco
2. University of California, San Francisco Center for Healthcare Value, San Francisco
3. Division of Epidemiology and Community Health, School of Public Health, University of Minnesota, Minneapolis
4. Division of Health Policy and Management, School of Public Health, University of Minnesota, Minneapolis
5. now at Drug Policy Program, Center for Research and Teaching in Economics, Aguascalientes, Aguascalientes, Mexico
6. Department of Medicine, University of California, San Francisco
7. Division of Research, Kaiser Permanente, Oakland, California
8. Department of Obstetrics and Gynecology, Global Health Institute, Duke University, Durham, North Carolina