Definition of Patent ductus arteriosus:

Patent ductus arteriosus (PDA) is a condition in which a blood vessel called the ductus arteriosus fails to close normally in an infant soon after birth. (The word "patent" means open.)

The condition leads to abnormal blood flow between the aorta and pulmonary artery, two major blood vessels that carry blood from the heart.

Causes, incidence, and risk factors:

Before birth, the ductus arteriosus allows blood to bypass the baby's lungs by connecting the pulmonary arteries (which supply blood to the lungs) with the aorta (which supplies blood to the body). Soon after the infant is born and the lungs fill with air, this blood vessel is no longer needed. It will usually close within a couple of days. If the ductus arteriosus does not close, there will be abnormal blood circulation between the heart and lungs.

PDA affects girls more often than boys. The condition is more common in premature infants and those with neonatal respiratory distress syndrome. Infants with genetic disorders, such as Down syndrome, and whose mothers had rubella during pregnancy are at higher risk for PDA.

PDA is common in babies with congenital heart problems, such as hypoplastic left heart syndrome, transposition of the great vessels, and pulmonary stenosis.