Objective: To determine the 1-year outcome of infants with isolated congenital heart block, the risk of fetal loss in mothers of affected infants, and the risk of recurrence of congenital heart block.
Methods: The outcomes of 34 infants with isolated congenital heart block and of the 109 pregnancies in the 32 mothers of these infants were analyzed retrospectively. A control group consisted of 170 pregnancies in 64 women individually matched for age, parity, and socioeconomic status.
Results: Five (15%) of the 34 infants with isolated congenital heart block died before 1 year of age. The relative risk for fetal loss in mothers of affected children, after the exclusion of a mother with 16 spontaneous abortions, was 1.9 (95% confidence interval 0.9-3.8; P = .094). The prevalence of congenital heart block in all siblings of children with congenital heart block was 4% (two of 45). The risk of having a child with congenital heart block after a previous birth of an affected child was 8% (two of 26).
Conclusions: Infant mortality in isolated congenital heart block is considerable, and mothers of affected children tend to have an increased risk of fetal loss. However, the risk of recurrence of congenital heart block is low.