1. Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, USA
2. Vincent Memorial Obstetrics and Gynecology Service, Andrology Laboratory and In Vitro Fertilization Unit, Massachusetts General Hospital, Boston, Massachusetts, USA
3. Department of Biostatistics, Harvard School of Public Health, Boston, Massachusetts, USA
4. National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, Georgia, USA