1. Department of Public Health, School of Public Health and Health Sciences, University of Massachusetts, Amherst, Massachusetts.
2. Channing Laboratory, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts.
3. Department of Epidemiology, Harvard School of Public Health, Boston, Massachusetts.
4. Department of Obstetrics and Gynecology, University of Iowa, Iowa City, Iowa.
5. Division of Preventive Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts.