Patent ductus arteriosus is a heart condition that affects babies when a blood vessel connecting two major arteries fails to close properly after birth, allowing blood to flow in the wrong direction and potentially placing extra strain on the tiny heart and lungs.

Understanding Patent Ductus Arteriosus

Patent ductus arteriosus, often shortened to PDA, is a congenital heart defect, which means it is present at birth. To understand this condition, it helps to know what happens during normal development. Before a baby is born, a blood vessel called the ductus arteriosus connects two major arteries: the aorta and the pulmonary artery. The aorta carries oxygen-rich blood from the heart to the rest of the body, while the pulmonary artery carries blood to the lungs.^[1]

While a baby is still in the womb, this connection is not only normal but necessary. The baby receives oxygen directly from the mother through the placenta, so the lungs do not need to work yet. The ductus arteriosus allows blood to bypass the baby’s lungs and flow directly to the body. This arrangement makes perfect sense for a developing baby who is not yet breathing air.^[3]

Once a baby is born and takes those first breaths, the lungs inflate and begin to work. At this point, the ductus arteriosus is no longer needed. In most babies, this blood vessel closes on its own during the first two days of life. However, when the ductus arteriosus stays open instead of closing, the result is called patent ductus arteriosus. The word “patent” means open in medical language.^[3]

When the opening remains, it creates a problem with blood flow. Oxygen-rich blood from the aorta can mix with oxygen-poor blood in the pulmonary artery, causing too much blood to flow into the lungs. This extra blood flow puts strain on both the heart and the lungs, forcing them to work much harder than they should. The severity of symptoms depends largely on how big the opening is.^[4]

How Common Is Patent Ductus Arteriosus

Patent ductus arteriosus is actually the most common heart condition found in newborn babies. The occurrence of this condition varies greatly depending on when a baby is born. In full-term infants born at the normal time, PDA occurs in only about one out of every two thousand births. In this population, it accounts for five to ten percent of all congenital heart disease cases.^[6]

The statistics change dramatically for babies born prematurely. The earlier a baby arrives, the more likely they are to have a patent ductus arteriosus. Studies show that about ten percent of babies born between thirty and thirty-seven weeks of pregnancy have PDA. For babies born between twenty-five and twenty-eight weeks, the rate jumps to eighty percent. For the tiniest and most premature babies born before twenty-four weeks of pregnancy, ninety percent will have a patent ductus arteriosus.^[4]

There is also a difference between boys and girls. Patent ductus arteriosus affects twice as many girls as boys. Researchers are still studying why this gender difference exists, but it has been consistently observed across different populations.^[3]

What Causes Patent Ductus Arteriosus

The exact cause of patent ductus arteriosus remains unclear to medical researchers. Scientists believe that genetics might play a role, as the condition can run in families. When one child in a family has PDA, there may be a slightly higher chance that siblings could also be affected.^[3]

Several specific circumstances are associated with a higher likelihood of PDA. One important factor is infection during pregnancy. Babies whose mothers had rubella, also known as German measles, during pregnancy have a higher risk of being born with patent ductus arteriosus. This is one reason why vaccination against rubella before pregnancy is so important for women’s health.^[4]

Babies with certain genetic conditions also have increased rates of PDA. For example, babies with Down syndrome are more likely to have this heart condition compared to babies without genetic disorders.^[3]

Lung problems at birth also appear connected to PDA. Babies who develop neonatal respiratory distress syndrome, a breathing problem that occurs when the lungs do not have enough of a lubricating substance called surfactant, are more likely to also have a patent ductus arteriosus. The relationship between lung problems and heart problems in premature babies creates additional challenges for their care.^[4]

In premature babies, the persistence of the ductus arteriosus is mainly linked to immaturity. The normal processes that cause the vessel to close—changes in oxygen levels and decreases in natural chemicals called prostaglandins—do not work properly when a baby is born too early. The body simply has not developed enough to complete this important transition.^[6]

Risk Factors for Developing PDA

Beyond the basic causes, several factors increase the risk that a baby will have patent ductus arteriosus. Premature birth stands out as the single most important risk factor. The degree of prematurity matters significantly—the earlier a baby is born, the greater the risk.^[10]

Certain conditions during the newborn period also raise the risk. Babies with respiratory distress syndrome face increased odds of PDA. Infections, particularly sepsis in the newborn period, are associated with higher rates of patent ductus arteriosus. Interestingly, receiving large volumes of intravenous fluids in the first week of life, more than one hundred seventy milliliters per kilogram of body weight per day, also increases PDA risk.^[10]

Some medications commonly used in newborn care can paradoxically increase the risk of PDA. Aminoglycoside antibiotics, frequently prescribed for infections, and certain antacids have been linked to higher rates of patent ductus arteriosus in studies. This creates a challenging situation for doctors who must balance treating infections with the potential risk to heart function.^[10]

On the positive side, some factors help protect against PDA. Mothers who receive steroid medications before a premature delivery have babies with lower rates of patent ductus arteriosus. The effect of these prenatal steroids on closing the ductus arteriosus works independently from their beneficial effects on lung development. Additionally, babies whose mothers had high blood pressure during pregnancy appear to have lower rates of PDA.^[10]

Male sex, while protective against some conditions, actually offers no advantage here—remember that PDA affects twice as many females as males, making female sex a risk factor. Prolonged rupture of membranes before birth and the use of furosemide, a medication that helps remove excess fluid, are also associated with increased PDA risk.^[10]

Signs and Symptoms of Patent Ductus Arteriosus

The symptoms that patent ductus arteriosus causes vary tremendously depending on the size of the opening. A small PDA might cause no symptoms at all. Some babies, children, and even adults with tiny openings never notice any problems and may only discover the condition during a routine medical examination. The only sign might be a heart murmur, an unusual sound the doctor hears when listening to the heart with a stethoscope.^[1]

A large patent ductus arteriosus, however, causes noticeable symptoms that usually appear soon after birth. Babies with large PDAs often struggle with feeding. They may show disinterest in eating or become tired very quickly during feedings. When feeding does occur, these babies might sweat excessively, which is not normal for healthy infants. Because they cannot take in enough nutrition, they grow poorly and gain weight slowly.^[3]

Breathing problems are another major symptom category. Babies with large PDAs breathe faster than normal and may appear to be working hard to breathe. They can become short of breath easily and tire quickly with any activity. The combination of breathing difficulties and feeding problems creates a cycle where the baby cannot get adequate nutrition because breathing and eating both require too much effort.^[4]

Physical examination reveals additional signs. The pulse may feel bounding, meaning it is stronger and more forceful than normal. The heart rate is often faster than expected for the baby’s age. These signs reflect the heart working harder to pump blood through the abnormal circulation pattern.^[3]

In older children or adults who somehow never had their PDA diagnosed in infancy, symptoms might be different. They may experience palpitations, which is the sensation of the heart beating unusually hard or fast. Some people report collapse episodes or fainting. They might notice shortness of breath, especially with physical activity or exercise. These symptoms reflect the long-term effects of years of abnormal blood flow.^[18]

Preventing Patent Ductus Arteriosus

Preventing patent ductus arteriosus focuses primarily on reducing the risk of premature birth, since prematurity is the strongest risk factor. Women who are pregnant can take several steps to promote a healthy, full-term pregnancy. Good prenatal care is essential. Regular visits to a healthcare provider throughout pregnancy allow early detection and management of any problems that might lead to premature delivery.^[10]

Vaccination plays an important preventive role. Women should ensure they are immune to rubella before becoming pregnant, as maternal rubella infection during pregnancy increases the risk of PDA in the baby. A simple blood test can check immunity, and vaccination is available for those who need it. However, the rubella vaccine must be given before pregnancy, not during it.^[4]

For women at risk of premature delivery, doctors may recommend steroid medications. These prenatal steroids help the baby’s lungs mature faster and also reduce the risk of patent ductus arteriosus. The protective effect of these steroids against PDA works through mechanisms that scientists are still studying, but the benefit has been clearly demonstrated in research.^[10]

Managing maternal health conditions is also important. Women with high blood pressure should work with their healthcare providers to keep it under control, although interestingly, maternal hypertension has been associated with lower PDA rates in babies. Women with diabetes, infections, or other health conditions should receive appropriate treatment throughout pregnancy.^[10]

After a baby is born, especially if premature, careful management of fluids and medications can potentially reduce PDA risk. Healthcare providers now know that excessive intravenous fluids in the first week after birth may increase the chance of PDA, so fluid management requires careful attention. Similarly, judicious use of certain medications that have been linked to increased PDA risk may help prevent the condition.^[10]

It is important to understand that not all cases of PDA can be prevented. The condition has genetic components and other factors that remain beyond current medical control. Even with excellent prenatal care and all appropriate preventive measures, some babies will still develop patent ductus arteriosus. When this happens, early detection and appropriate treatment become the focus.

How Patent Ductus Arteriosus Affects the Body

Understanding what happens in the body with patent ductus arteriosus requires looking at how blood normally flows through the heart and lungs. In healthy circulation after birth, blood that has delivered oxygen to the body returns to the right side of the heart. The right side pumps this oxygen-poor blood to the lungs, where it picks up fresh oxygen. This oxygen-rich blood then returns to the left side of the heart, which pumps it out through the aorta to supply the entire body.^[7]

When patent ductus arteriosus exists, this orderly flow becomes disrupted. The opening between the aorta and pulmonary artery creates what doctors call a left-to-right shunt. Blood from the aorta, which should be heading to the body, instead flows backward through the ductus arteriosus into the pulmonary artery. This means extra blood gets pumped to the lungs that has already been oxygenated.^[7]

The lungs receive more blood flow than they should handle. This excess blood in the lung circulation increases pressure in the pulmonary arteries, a condition called pulmonary hypertension. The delicate blood vessels in the lungs were not designed to handle such high volumes or pressures. Over time, if left untreated, these vessels can become damaged. The lung tissue itself may accumulate extra fluid, making breathing even more difficult.^[4]

The heart must work much harder than normal. The left side of the heart, which should only pump blood once to the body, now effectively pumps some of that blood multiple times as it recirculates through the PDA to the lungs. This extra workload causes the heart muscle to enlarge, particularly the left ventricle and left atrium. Eventually, this can lead to heart failure, where the heart cannot keep up with the body’s demands despite working overtime.^[1]

The amount of these problems depends critically on the size of the ductus arteriosus opening. A small PDA might shunt only a little extra blood, causing minimal strain. The heart and lungs can compensate relatively easily, and symptoms may never appear. A large PDA creates a massive extra burden. The volume of blood being shunted can overwhelm the system, leading to fluid in the lungs, breathing problems, and heart enlargement in a matter of weeks or even days.^[7]

Another important factor is pulmonary vascular resistance, which is the resistance that blood encounters flowing through the lung vessels. In newborns, this resistance is naturally high but drops quickly after birth. The drop in resistance actually makes PDA potentially more problematic because it allows more blood to flow through the opening. This is why some babies develop symptoms in the days or weeks after birth rather than immediately.^[7]

In addition to the immediate effects on heart and lung function, patent ductus arteriosus creates vulnerability to other complications. The abnormal blood flow patterns can contribute to kidney problems, as the kidneys may not receive adequate blood flow. Babies with PDA have higher rates of a serious intestinal condition called necrotizing enterocolitis, where portions of the intestine become damaged. Bleeding in the brain, called intraventricular hemorrhage, occurs more frequently in premature babies with PDA.^[6]

Nutrition and growth suffer as well. The extra work of breathing and the heart’s increased effort burn more calories. Meanwhile, breathing difficulty and fatigue make feeding harder. The combination means babies with PDA often cannot take in enough nutrition to grow properly, even as their bodies require extra energy. Poor growth becomes both a symptom and a consequence of the condition.^[6]

The changes associated with PDA also create risk for infection. The turbulent blood flow through the abnormal connection can damage the lining of blood vessels and heart valves. Bacteria circulating in the bloodstream, which would normally pass through harmlessly, can stick to these damaged areas and cause endocarditis, a serious infection of the heart’s inner lining. This is why even small PDAs that cause no symptoms may warrant closure—to prevent this dangerous complication.^[12]

If patent ductus arteriosus remains untreated for months or years, particularly large ones, the constant high pressure and high blood flow to the lungs can cause permanent changes in the pulmonary blood vessels. They can become thick and stiff, a condition called pulmonary vascular obstructive disease. Eventually, the resistance in the lung vessels may become so high that blood flow actually reverses, going from right to left instead of left to right. This reversal causes oxygen-poor blood to mix into the body’s circulation, resulting in a blue tint to the skin. This late complication, though now rare due to early treatment, can be fatal.^[12]