[1] FHI 360, Global Hlth Populat & Nutr Dept, Durham, NC 27701 USA
[2] Univ Cape Town, Sch Publ Hlth & Family Med, Div Epidemiol & Biostat, Cape Town, South Africa
[3] CUNY, Sch Publ Hlth, Dept Epidemiol & Biostat, New York, NY USA
[4] Rutgers State Univ, Inst Hlth Care Policy & Aging Res, Dept Stat, Piscataway, NJ USA
[5] Univ Cape Town, New Somerset Hosp, Dept Obstet & Gynaecol, Cape Town, South Africa