Whether the pregnant woman herself has congenital heart disease or the fetus has congenital heart disease, it can usually be detected during the pregnancy test. This is because after a woman becomes pregnant, she needs to have an electrocardiogram (ECG) checked in the third trimester of pregnancy. If there is congenital heart disease, the ECG will show an abnormal state, and then the doctor will recommend a cardiac ultrasound to further confirm the diagnosis of congenital heart disease. If the fetus has congenital heart disease, then a 4D ultrasound will be done at the 24th week of pregnancy, at which time it will be able to check for fetal heart abnormalities.