1. Department of Public Health, University of Massachusetts, Amherst, Massachusetts.
2. Channing Laboratory, 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 Nutrition, Harvard School of Public Health, Boston, Massachusetts.
5. Department of Obstetrics and Gynecology, University of Iowa, Iowa City, lowa.
6. Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts.