Congenital heart diseases are abnormalities of the heart's structure and function caused by abnormal or disordered heart development before birth.

Congenital heart disease (CHD) is a broad term that can describe a number of different abnormalities affecting the heart. Congenital heart disease is, by definition, present at birth although its effects may not be obvious immediately. In some cases, such as coarctation of the aorta, it may not present itself for many years and a few lesions such as a small ventricular septal defect (VSD) may never cause any problems and are compatible with normal physical activity and a normal life span.

According to the American Heart Association, approximately 35,000 babies are born each year with some type of congenital heart defect. Congenital heart disease is responsible for more deaths in the first year of life than any other birth defects. Many of these defects need to be followed carefully; though some heal over time, others will require treatment

Some congenital heart diseases can be treated with medication alone, while others require one or more surgeries. The risk of death from congenital heart disease surgery has dropped from approximately 30% in the 1970s to less than 5% in most cases today.

Congenital heart disease is often divided into two types: those with cyanosis (blue discoloration caused by a relative lack of oxygen) and those without cyanosis. The following lists cover the most common of the congenital heart diseases:

Cyanotic:

• Tetralogy of Fallot
• Transposition of the great vessels
• Tricuspid atresia
• Total anomalous pulmonary venous return
• Truncus arteriosus
• Hypoplastic left heart
• Hypoplastic right heart
• Ebstein's anomaly

Non-cyanotic:

• Ventricular septal defect (VSD)
• Atrial septal defect (ASD)
• Patent ductus arteriosus (PDA)
• Aortic stenosis
• Pulmonic stenosis
• Coarctation of the aorta
• Atrioventricular canal (endocardial cushion defect)

These abnormalities may occur as single defects or in various combinations. VSD is the most commonly diagnosed congenital heart defect (about one-third of all cases) and it is seen almost three times as often as ASD and PDA, which are the next most common.

The majority of congenital heart diseases occur as an isolated defect and are not associated with other diseases. However, they can also be a part of various genetic and chromosomal syndromes, such as Down syndrome, trisomy 13, Turner's syndrome, Marfan syndrome, Noonan syndrome, Ellis-van Creveld syndrome.

Drugs, chemicals, and infections during pregnancy can also cause congenital heart abnormalities. Fetal rubella, maternal alcohol use (fetal alcohol syndrome), and use of retinoic acid (for acne) are some causes of congenital heart disease in an infant.