Patent ductus arteriosus (PDA) is a heart condition in which a blood vessel that normally closes shortly after birth stays open instead. This vessel, called the ductus arteriosus, connects two major arteries leaving the heart. While every baby has it in the womb, it typically closes on its own within the first day or two of life. When it doesn’t, blood flows in the wrong direction, forcing the heart and lungs to work harder than they should.
PDA is one of the most common congenital heart defects, accounting for 5% to 10% of all congenital heart disease in full-term infants. It occurs in about 1 in 2,000 full-term births, but the rates are dramatically higher in premature babies: 20% to 60% of preterm infants have a PDA, and among babies weighing less than 1,200 grams (about 2.6 pounds) at birth, the rate reaches 80%.
Why This Vessel Exists and How It Normally Closes
Before birth, a baby’s lungs aren’t doing any work. Oxygen comes from the placenta through the umbilical cord, so blood doesn’t need to pass through the lungs to pick up oxygen. The ductus arteriosus acts as a shortcut, routing blood away from the lungs and sending it straight to the rest of the body. A hormone-like substance called prostaglandin E2, produced in part by the placenta, keeps this vessel open throughout pregnancy.
The moment a baby takes its first breath, everything changes. The lungs inflate, and the resistance to blood flow in the lungs drops sharply. Blood starts flowing into the lungs on its own. At the same time, the placenta is gone, which cuts off the supply of prostaglandins that were keeping the ductus open. The rise in oxygen levels in the blood triggers the muscular wall of the ductus to contract. In healthy, full-term newborns, this vessel functionally closes within 12 to 24 hours. Permanent structural closure follows within two to three weeks.
In premature infants, the muscles in the ductus wall are less mature and less responsive to oxygen. The vessel simply doesn’t constrict the way it should, and it stays open.
What Happens When the Ductus Stays Open
Once a baby is breathing on its own, pressure in the lungs is much lower than pressure in the body’s main artery (the aorta). If the ductus remains open, blood that should be heading out to the body gets redirected backward into the lungs. This is called a left-to-right shunt. The lungs receive more blood than they need, and the heart has to pump harder to compensate.
A small PDA may cause no problems at all. Many small openings close on their own over time, and the baby may never show symptoms. A larger opening, however, forces the heart to handle a significantly increased volume of blood. Over time, this extra workload can stretch and weaken the heart, lead to fluid buildup in the lungs, and raise pressure in the pulmonary arteries. Left untreated, a large PDA can cause heart failure, permanent damage to the blood vessels in the lungs (pulmonary hypertension), and in severe cases, can be life-threatening.
Signs and Symptoms
The hallmark of PDA is a distinctive heart murmur. Unlike most heart murmurs that occur during only one phase of the heartbeat, a PDA murmur is continuous, meaning it runs through both the pumping and resting phases. When it’s loud, doctors describe it as sounding like machinery, a steady, rumbling quality that’s heard best near the upper left side of the chest.
Beyond the murmur, a baby with a significant PDA often has bounding pulses, meaning the pulse feels unusually strong and forceful because of the wide swings in blood pressure caused by the shunt. In premature infants, doctors may also notice that the chest visibly moves with each heartbeat (a hyperdynamic precordium). Babies with larger shunts can develop signs of heart failure: rapid breathing, poor feeding, slow weight gain, and excessive sweating during feeding.
How PDA Is Diagnosed
While the murmur raises suspicion, the definitive diagnosis comes from an echocardiogram, an ultrasound of the heart. This imaging lets doctors see the open vessel directly and measure how much blood is flowing through it.
Doctors classify PDA by size and by how much it disrupts normal blood flow. A small PDA measures less than 1.5 millimeters across at its narrowest point. A moderate one falls between 1.5 and 3 millimeters, and a large PDA exceeds 3 millimeters. Size alone doesn’t tell the full story, though. What matters more is whether the PDA is “hemodynamically significant,” meaning it’s moving enough blood to strain the heart and lungs. Doctors look for specific patterns on the echocardiogram to determine this: reversed blood flow in the aorta (meaning blood is being stolen from the body to flow back to the lungs), an enlarged left side of the heart, and increased blood flow through the lung arteries. When the left side of the heart stretches beyond a certain ratio compared to the aorta, it signals that the lungs are receiving too much blood and the heart is under real stress.
Treatment: When to Act and When to Wait
The approach to treating PDA has shifted significantly in recent years. A 2025 consensus report from the American Academy of Pediatrics now recommends expectant management (essentially, watchful waiting) as the default approach for preterm infants. Routinely treating every PDA with medication, regardless of whether it’s causing problems, does not improve outcomes. Prophylactic treatment is now strongly discouraged based on evidence from over 130 randomized controlled trials showing no benefit for survival or lung disease prevention.
This means many premature infants with a PDA will simply be monitored. Many of these openings close on their own, particularly in the first two weeks of life. The key decision point is whether the PDA is hemodynamically significant. If echocardiography shows the shunt is large enough to burden the heart and compromise blood flow to the brain, gut, or kidneys, then intervention becomes appropriate.
Medication
When treatment is needed, the first option is usually medication that blocks the production of prostaglandins, the same substances that kept the ductus open before birth. Three drugs are used for this purpose, and their closure rates are broadly similar: roughly 64% to 72% of PDAs close with a course of medication. The choice between them often depends on the baby’s other medical conditions, since some of these drugs carry risks to the kidneys or gut.
Procedures for Closure
If medication doesn’t work or can’t be used safely, the next step is physically closing the ductus. Traditionally, this meant surgical ligation: a surgeon makes a small incision between the ribs on the left side and ties off or clips the vessel. This is effective but involves opening the chest, general anesthesia, and the stresses of surgery on a very small body.
Increasingly, doctors can close the PDA using a catheter-based approach. A thin tube is threaded through a blood vessel (usually in the leg) up to the heart, and a small device is placed inside the ductus to block it. This technique has been used successfully in babies as small as 1.5 kilograms (about 3.3 pounds) and as early as 23 weeks gestational age. It avoids the need for chest surgery, though it requires specialized equipment and expertise.
Recovery After Closure
For babies who undergo surgical ligation, the hospital stay typically lasts two to five days. The first day or two are spent in the intensive care unit with close monitoring, breathing support if needed, and IV medications. By day three to five, most babies have moved to a regular pediatric ward and are sitting up or beginning to move around. Follow-up appointments in the weeks and months afterward track heart function and overall development.
Catheter-based closure generally involves a shorter and less painful recovery, since there’s no chest incision to heal. Either way, the long-term outlook after successful PDA closure is excellent. Once the vessel is sealed, the extra blood flow to the lungs stops immediately, and the heart begins to recover from the added workload. Most children go on to live completely normal lives with no lasting heart problems.