1. School of Public Health, University of California at Berkeley, Berkeley, California, USA
2. Department of Obstetrics and Gynecology, University of Wisconsin Medical School, Madison, Wisconsin, USA
3. School of Public Health, State University of New York, Albany, New York, USA
4. Department of Obstetrics and Gynecology, Mangiagalli Hospital, University of Milan, Milan, Italy
5. Department of Laboratory Medicine, University of Milano-Bicocca, School of Medicine, Hospital of Desio, Desio-Milano, Italy
6. Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, Georgia, USA