[1] Univ Calif Berkeley, Sch Publ Hlth, Berkeley, CA 94720 USA
[2] RTI Int, San Francisco, CA USA
[3] Ibis Reprod Hlth, Cambridge, MA USA
[4] MRC, Kwa Zulu, South Africa
[5] Univ Calif San Francisco, Univ Zimbabwe, Collaborat Programme Womens Hlth, Harare, Zimbabwe
[6] Univ Witwatersrand, Perinatal HIV Res Unit, Johannesburg, South Africa
[7] Univ Calif San Francisco, Dept Med, Ctr AIDS Prevent Studies, San Francisco, CA USA