1. Texas A&M Health Science Center; School of Rural Public Health; College Station; Texas
2. Slone Epidemiology Center at Boston University; Boston; Massachusetts
3. Texas Department of State Health Services; Environmental Epidemiology and Disease Registries; Austin; Texas
4. Texas Department of State Health Services; Birth Defects Epidemiology and Surveillance Branch; Austin; Texas
5. Department of Epidemiology; College of Public Health; University of Iowa; Iowa City; Iowa
6. Department of Pediatrics; College of Medicine; University of Arkansas for Medical Sciences; Little Rock; Arkansas