1. Department of Obstetrics and Gynecology; Duke University; Durham NC USA
2. UZ-UCSF Collaborative Programme on Women's Health; Harare Zimbabwe
3. Ibis Reproductive Health; Cambridge MA USA
4. South African Medical Research Council HIV Prevention Research Unit; Durban South Africa
5. Department of Epidemiology and Biostatistics; University of California; San Francisco CA USA
6. Department of Obstetrics, Gynecology and Reproductive Sciences, Bixby Center for Global Reproductive Health; University of California; San Francisco CA USA
7. Department of Obstetrics and Gynecology; University of California; Los Angeles CA USA