1. Departments of Pediatrics,
2. Epidemiology and Biostatistics,
3. Philip R. Lee Institute for Health Policy Studies, University of California, San Francisco, San Francisco, California;
4. Department of Obstetrics and Gynecology, Oregon Health & Sciences University, Portland, Oregon;
5. Medicine, and
6. Department of Pediatrics, Kaiser Permanente, San Francisco, California; and
7. Department of Pediatrics, California Pacific Medical Center, San Francisco, California