[1] Johns Hopkins Bloomberg Sch Publ Hlth, Dept Epidemiol, Baltimore, MD USA
[2] Univ Washington, Dept Global Hlth, Seattle, WA 98195 USA
[3] Univ Nairobi, Dept Obstet & Gynaecol, Nairobi, Kenya
[4] Univ Nairobi, Dept Paediat, Nairobi, Kenya
[5] Univ Washington, Dept Med, Seattle, WA USA
[6] Univ Washington, Dept Epidemiol & Global Hlth, Seattle, WA 98195 USA