While in the mother’s womb, the baby’s lungs do not need to breathe because the baby can get the oxygen it needs from the mother through the placenta. Since the baby’s lungs do not need to breathe, there is no need for blood to enter the pulmonary circulation. At that time, every baby has an arterial duct, whose function is that the blood in the pulmonary artery can pass through the duct into the aorta, thus bypassing the lungs, which do not need blood flow. When the baby is born, the umbilical cord is cut. The baby’s lungs need to perform the role of supplying oxygen to the body. This is when air is available to the lungs and blood flow to the lungs occurs. The ductus arteriosus usually closes automatically within the first few hours of your baby’s life. However, if the baby’s ductus arteriosus does not close on its own and remains open, an undescended ductus arteriosus develops. This condition is more common in premature babies, although it can sometimes occur in full-term babies. What are the signs and symptoms of ductus arteriosus? The signs and symptoms of ductus arteriosus depend on the diameter of the ductus arteriosus and the amount of blood flow in the ductus arteriosus. After birth, the blood pressure and vascular resistance in the aorta are higher than in the pulmonary artery, so the ductus arteriosus directs some of the blood flow from the aorta into the pulmonary artery. In premature babies, the lungs are not fully developed and, on this basis, if ductus arteriosus occurs, the baby may show signs of heart failure and may require ventilatory support. When a newborn presents with shortness of breath, labored breathing, frequent respiratory infections, and poor growth, the ductus arteriosus should be considered as the cause. However, if the diameter of the ductus arteriosus is small, there may be no outward symptoms and it may be detected only by a heart murmur heard by a physician during a physical examination. Even if there are no symptoms, the turbulent flow of blood through the ductus arteriosus increases the chance of bacterial infection within the heart, a serious bacterial infection known as infective endocarditis. How is the diagnosis of ductus arteriosus confirmed? Because the blood flow through the ductus arteriosus is turbulent, this can produce a characteristic heart murmur that can be detected by the physician during auscultation. This characteristic heart murmur, combined with the signs of heart failure in preterm infants, usually suggests a diagnosis of ductus arteriosus. Chest radiographs can reveal the enlarged heart and increased blood flow to the lungs that are often seen in ductus arteriosus. A cardiac ultrasound can confirm the diagnosis of ductus arteriosus. Cardiac ultrasound can also measure the diameter of the ductus arteriosus and the degree of enlargement of the heart. In older children, abnormal blood flow through the ductus arteriosus can be detected by cardiac ultrasound even if the chest radiograph is completely normal, thus confirming the diagnosis of ductus arteriosus.