1. University of North Carolina School of Medicine; Chapel Hill North Carolina
2. Department of Epidemiology; University of North Carolina at Chapel Hill; Chapel Hill North Carolina
3. Department of Surgery; University of North Carolina School of Medicine; Chapel Hill North Carolina
4. North Carolina State Center for Health Statistics Birth Defects Monitoring Program; Raleigh North Carolina
5. Department of Maternal and Child Health; University of North Carolina at Chapel Hill; Chapel Hill North Carolina
6. Department of Cardiothoracic; Surgery Nemours Children's Hospital; Orlando FL USA