Atresia (ah-TREE-zhah) is a condition in which a baby is born with a missing or closed valve or tube somewhere in his or her body. Pulmonary atresia is a rare defect in which a baby is born with an abnormally developed pulmonary heart valve (which is between two of the heart's chambers) that doesn't open. This prevents blood from flowing through the heart and into the lungs to receive oxygen. Treatments include medications and surgery. More to Know Air, blood, bodily fluids, and waste products travel throughout the body in a system of vessels, tubes, and chambers that are often separated by valves. When a child is born with atresia, it means that a valve is missing or a tube is closed off. This interrupts the normal flow of blood, fluid, waste, or air, which can lead to a number of complications. Most kinds of atresia are serious and can be fatal if they go untreated. Treatment usually involves surgery while the child is still an infant. Atresia can affect many body parts, including the nose, ears, organs, digestive tract, and heart. The types of atresia are named for the body parts they affect: Tricuspid atresia and aortic atresia also involve valves in the heart. Biliary atresia is a defect in the liver or bile system. Choanal atresia is a defect of the nasal passages (choana). Anal atresia (imperforate anus) and esophageal atresia are defects of the digestive tract. Keep in Mind Most kinds of atresia can be treated successfully with surgery; some cases may require more than one operation. All A to Z dictionary entries are regularly reviewed by KidsHealth medical experts. Back to Articles Related Articles Congenital Heart Defects Heart defects happen when there's a problem with a baby's heart development during pregnancy. Most heart defects can be treated during infancy. Read More Birth Defects Some birth defects are minor and cause no problems; others cause major disabilities. Learn about the different types of birth defects, and how to help prevent them. Read More When Your Baby Has a Birth Defect If your child has a birth defect, you don't have to go it alone - many people and resources are available to help you. Read More Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. © 1995-2021 KidsHealth®. All rights reserved. Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.