1. Slone Epidemiology Center; Boston University; Boston MA
2. Department of Orthopaedic Surgery; Boston Children's Hospital; Boston MA
3. North Carolina Birth Defects Monitoring Program; State Center for Health Statistics; Raleigh NC
4. Massachusetts Birth Defects Monitoring Program; Massachusetts Department of Public Health; Center for Birth Defects Research and Prevention; Boston MA
5. Congenital Malformations Registry; New York State Department of Health; Albany NY