Incidence of cardiac malformations at birth and later, and neonatal mortality.

Malformations of the heart are found in about 8 of every 0OOO births. In addition, about 4 of every 0OOO births have bicuspid aortic valves, but they are rarely recognized early in life. Apart from these, ventricular septal defect is much the commonest malformation, forming about 30 per cent of all others. Probably small ventricular septal defects and bicuspid aortic valves are common because they have few drawbacks during the reproductive period so are hardly checked by natural selection. Atrial septal defect and persistent ductus arteriosus come next, each forming about IO per cent. Pulmonary stenosis and aortic coarctation each form about 7 per cent. Aortic stenosis and Fallot's tetralogy form about 6 per cent and transposition of the great trunks 4 per cent. These 8 malformations are responsible for 8o per cent of the total, but many less common ones have been listed. The neonatal mortality is so high that the incidence of all cardiac malformations is soon reduced to about half its incidence at birth. The mortality rates are strikingly different. They are about go per cent for transposition and truncus, reducing these to insignificant proportions in older children. They are between 50 and 6o per cent for aortic coarctation, because most with preductal coarctation die early, for Fallot's tetralogy, and for those with multiple malformations. For other common malformations they are probably higher for ventricular and atrial septal defects (both about 36%), than for aortic stenosis (about 29%) and lower for pulmonary stenosis (24%) and persistent ductus arteriosus (23%). The prominence of ventricular septal defect at birth is reduced by the large number that close spontaneously, and this applies also to persistent ductus arteriosus but to a lesser extent. The observed incidence in schoolchildren and in older children and young adults is described. This agrees reasonably well with the figures calculatedfrom the incidence at birth and the differential mortality, neonatal and during the first two decades. At birth, bicuspid aortic valves, aortic stenosis, coarctation, and most cyanotic conditions have a higher male incidence which continues or increases at older ages. Only persistent ductus arteriosus has a higher female incidence at birth and it too increases with age, but adults with atrial septal defect and ventricular septal defect show an increasing female incidence. Only pulmonary stenosis shows no difference between the