1. Department of Medicine, University of Michigan, Ann Arbor, Michigan.
2. Department of Obstetrics and Gynecology, University of Michigan, Ann Arbor, Michigan.
3. Department of Statistics, Purdue University, West Lafayette, Indiana.
4. Children's Hospital Oakland Research Institute, Oakland, California.
5. Departments of Obstetrics and Gynecology, University of Southern California, Los Angeles, California.
6. Department of Medicine, University of California, Los Angeles, Los Angeles, California.
7. Department of Epidemiology, University of Michigan, Ann Arbor, Michigan.
8. Department of Medicine, University of California, San Francisco, California.
9. Department of Epidemiology, University of California, San Francisco, California.
10. Department of Biostatistics, University of California, San Francisco, California.