1. a School of Public Health , University of California , Berkeley , CA , USA
2. b Women's Global Health Imperative , RTI International , San Francisco , CA , USA
3. c Ibis Reproductive Health , Cambridge , MA , USA
4. d Medical Research Council , Kwazulu-Natal , South Africa
5. e University of Zimbabwe-University of California San Francisco Research Collaborative Programme in Women's Health , Harare , Zimbabwe
6. f Perinatal HIV Research Unit , University of Witwatersrand , Johannesburg , South Africa
7. g Department of Medicine, Center for AIDS Prevention Studies , University of California San Francisco , San Francisco , CA , USA