1University of Zimbabwe-University of California at San Francisco Collaborative Research Program in Women's Health, Harare, Zimbabwe.2Department of Medical Laboratory Sciences, University of Zimbabwe, Harare, Zimbabwe.3Department of Obstetrics and Gynecology, University of Zimbabwe, Harare, Zimbabwe.4Department of Obstetrics, Gynecology, and Reproductive Science, University of California at San Francisco, California.5Department of Epidemiology and Biostatistics, University of California at San Francisco, California.