Cases in which congenital heart disease was part of a genetic complex were evaluated separately for environmental exposures. Genetic data analysis focused on first degree relatives but extended family data were noted wherever available. The genetic data analyses included: estimation of recurrence risks in siblings for congenital heart disease with the same cardiac defect; any cardiac defect in the sibling; non cardiac birth defect and pregnancy loss in the family. Parental phenotype was investigated for the presence of birth defects and known genetic disorders. Twin births were assessed for concordance in zygosity. Hypotheses of genetic and environmental teratogenic and coteratogenic interactions were tested. Pathogenic mechanisms were further defined through anatomic and echocardiographic observations. The family inquiry was expanded to include cousins. Nutrition information was added on maternal vitamin A supplementation, protein, calories, and other nutrients.