The epidemiology of three serious cardiac defects. A joint study between five centres.

The paper reports a joint study made by five member programs of the International Clearinghouse for Birth Defects Monitoring Systems. Three specific heart malformations were studied, hypoplastic left heart syndrome (HLHS), transposition of the great vessels (TGV), tetralogy of Fallot, and some epidemiological characteristics were analyzed. The prevalence at birth was estimated to be 2.0, 2.9, and 2.2 per 10,000 births, respectively. No time trend in the prevalence at birth was observed for any one of the three malformations in the total study population. When only isolated defects were considered (infants without major non-cardiac malformations), all three cardiac anomalies showed an increased rate in infants with low birth weight, short gestational duration and probably twinning. A preponderance for males was observed for each defect but was strongest among infants with tetralogy of Fallot (sex ratio 2.5 for Fallot, 1.4 to 1.5 for the other conditions). There were also differences between the three cardiac defects with respect to percentage of low birth weight, preterm births, and rate and type of associated extracardiac malformations. This paper stresses the advantage of pooling data from different registries in studies of uncommon specific malformations and infrequent characteristics.