Risks to the offspring of patients with some common congenital heart defects.

The families of 424 adult index patients with ventricular septal defect, right ventricular outflow tract obstruction, or combinations of these two abnormalities, were visited and interviewed, and whenever possible the children of index patients were examined clinically. Congenital heart defects were present in 9 of 308 children, 8 of 899 sibs, 4 of 840 parents, and 4 of 731 nephews and nieces of the index patients. The last three figures are likely to be underestimates owing to the design of the study. Comparison of pairs of affected relatives suggests that the group of lesions studied may have genetic determinants in common.