Congenital Heart Disease What is a congenital heart defect Congenital means from birth. A congenital heart defect is an abnormality of the heart that has been present from birth. How common are these defects At least 8 out of every 1000 babies born each year have a heart defect. About half of these babies have a minor defect and will not need any treatment but the rest will need medical treatment or surgery. What caused the defect In most cases the cause is unknown, although some defects are ...