[1] Univ Witwatersrand, Dept Obstet & Gynaecol, Match Res Maternal Adolescent & Child Hlth Res, Durban, South Africa
[2] Sch Hyg & Trop Med, Fac Epidemiol & Populat Hlth, London, England
[3] Florida Int Univ, Stempel Coll Publ Hlth & Social Work, Dept Epidemiol, 11200 SW 8th St,AHC 5-Rm 482, Miami, FL 33199 USA
[4] World Hlth Org, Dept Reprod Hlth & Res, Special Program Res Dev & Res Training Human Repr, Geneva, Switzerland