Fetal and infant death, twinning and cardiac malformations in families of 2,000 children with and 500 without cardiac defects.

Analysis of family data on 2,000 children with a congenital cardiac malformation of unknown origin and 500 with an innocent murmur showed the incidence of twinning in probands, siblings and parents to be the same as in the general population. The mothers in the two groups of probands had the same incidence of spontaneous abortions and stillbirths. There was a small increase in infant mortality in siblings of probands with a cardiac malformation, but this could be accounted for by the increased incidence of cardiac malformations. The latter occurred in 1.4 percent of all siblings and in 1.7 percent of later born siblings. Complete concordance for malformation type occurred in 31 percent of affected siblings and 46 percent of affected parents, and partial concordance occurred in an additional 21 and 8 percent, respectively. Combined direct and indirect observations and calculations indicate that the risk of recurrent cardiac malformations is 1.4 to 3 percent in families in which one child was born with a cardiac malformation of unknown origin; no significant difference was evident for the various cardiac malformations.