[1] Univ N Carolina, Dept Epidemiol, Gillings Sch Global Publ Hlth, Chapel Hill, NC 27515 USA
[2] Duke Univ, Dept Obstet & Gynecol, Durham, NC USA
[3] Duke Univ, Duke Global Hlth Inst, Durham, NC USA
[4] Univ Calif Los Angeles, Dept Epidemiol, Los Angeles, CA USA
[5] Univ Calif Los Angeles, Dept Stat, Los Angeles, CA USA
[6] Univ N Carolina, Sch Med, Dept Med, Div Infect Dis, Chapel Hill, NC USA