Epidemiology of major congenital heart defects in Sweden, 1981-1986.

STUDY OBJECTIVE The aim was to make an epidemiological study of major congenital heart defects and to make comparisons between groups of heart defects regarding different epidemiological variables. DESIGN The cases with congenital heart defects were identified from two Swedish registries: the Registry of Congenital Malformations and the Child Cardiology Registry. A classification with nine groups of heart defects is proposed. SETTING This was a national survey in Sweden during the period 1981-1986. The total number of cases reported during the six years was 1605. Cases that presented a patent ductus arteriosus only and a birthweight below 2500 g were excluded. MEASUREMENTS AND MAIN RESULTS The prevalence at birth was 2.8 per 1000. When cases with a chromosomal anomaly were excluded, no maternal age effect was observed except a possible under-risk for women above 40 years. The risk for a heart defect seems to increase with increasing parity independent of age. A higher risk was also observed among twin infants compared with singletons although no specificity in cardiac malformation type appeared. Sex ratio, the tendency for having an associated extracardiac malformation, and the proportion of isolated v non-isolated cardiac defects differed between the different groups of heart malformations. CONCLUSIONS The differences observed between groups of defects indicate different aetiologies and show that this classification may be suitable for further analyses of congenital heart defects.