Congenital heart defects affect how blood flows through the heart and out to the rest of the body. Congenital means they are present at birth. Heart defects can vary from mild (a small hole in the heart) to severe (missing parts of the heart).

In the United States, heart defects affect nearly 1% of births, or about 40,000 babies, each year. About 1 in 4 babies born with a heart defect has a critical heart defect. Babies with critical heart defects need surgery or other procedures in the first year of life.