1. Department of Epidemiology, Mailman School of Public Health, Columbia University , New York, NY, USA
2. Institute for Global Health and Infectious Diseases, School of Medicine, University of North Carolina at Chapel Hill , Chapel Hill, NC, USA
3. Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill , Chapel Hill, NC, USA
4. Department of Obstetrics and Gynecology, School of Medicine, University of North Carolina , Chapel Hill, NC, USA