1. Department of Pediatrics (Neonatology), Arkansas Children's Hospital University of Arkansas for Medical Sciences Little Rock Arkansas USA
2. Arkansas Center for Birth Defects Research and Prevention Little Rock Arkansas USA
3. Department of Environmental and Occupational Health, Fay W. Boozman College of Public Heath University of Arkansas for Medical Sciences Little Rock Arkansas USA
4. Department of Biostatistics, Fay W. Boozman College of Public Heath University of Arkansas for Medical Sciences Little Rock Arkansas USA
5. Division of Public Health Sciences Washington University in St. Louis St Louis Missouri USA
6. Department of Epidemiology, Fay W. Boozman College of Public Heath University of Arkansas for Medical Sciences Little Rock Arkansas USA