1. National Center for Health Statistics, Centers for Disease Control and Prevention, Hyattsville, MD (current affiliation, Department of Human and Community Development, University of California, Davis, Davis, CA)
2. Department of Family and Community Medicine, University of California, San Francisco, San Francisco, CA
3. California Department of Health Services, Sacramento, CA
4. Perinatal Epidemiology, National Center for Health Statistics, Centers for Disease Control and Prevention, Hyattsville, MD