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