Seventy-seven live born children (September 1988 to May 1993) had prenatally detected morphological cardiac malformations (61 cases) and/or arrhythmias (17 cases). The outcome of these children was analysed with an average follow-up of 21.4 months (range: 1 day to 11 years). The parameters studied were age and condition of prenatal diagnosis, the term of pregnancy, the extracardiac malformations associated and the outcome of the live born children. Fifty-two children survived with a mean follow-up of 28.2 months (range: 5 months to 11 years) and 25 children died at a mean age of 3.3 months (range: 1 day to 32 months). The cardiac malformations correlated with the postnatal diagnosis in 59 children (60 cardiac malformations). They included left or right outflow tract obstruction in 22%, septal defects or Tetralogy of Fallot with or without pulmonary atresia in 18.4%, arterial malposition in 12.9% and arrhythmias or conduction defects in 20.7% of cases. The main reason for the high mortality was the complexity of the cardiac malformations with, in particular, ventricular hypoplasia with right or left outflow tract obstruction (41% of mortality). The functional consequences of these abnormalities were only partially appreciated at prenatal diagnosis. The extracardiac malformations, more easily diagnosed, contributed less to this mortality rate. The favourable prognosis of the arrhythmias or conduction defects diagnosed prenatally was confirmed but was, however, associated with a mortality rate of 12%.(ABSTRACT TRUNCATED AT 250 WORDS)