1. 1Department of Obstetrics and Gynecology, Vanderbilt University Medical Center, Nashville, Tennessee;
2. 2Division of Infectious Diseases, Department of Medicine, University of Cincinnati, Cincinnati, Ohio;
3. 3Department of Gynecology and Obstetrics, Emory University School of Medicine, Atlanta, Georgia;
4. 4Center for Biomedical Research, Population Council, New York, New York