1. Department of Epidemiology, Harvard School of Public Health and
2. Harvard College, Faculty of Arts and Sciences, Harvard University, Cambridge, Massachusetts, USA
3. Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
4. Obstetrics and Gynecology Epidemiology Center, Department of Obstetrics, Gynecology and Reproductive Biology, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts USA