Congenital heart disease is a condition where the structure of the heart is different from normal before a baby is even born. These differences can range from tiny holes that may never cause problems to serious issues that need immediate attention. With better understanding and care, many people with these heart conditions now live full, active lives well into adulthood.

How Common Is Congenital Heart Disease

Congenital heart disease stands as the most common type of birth defect affecting babies worldwide. In the United States, approximately 1 out of every 100 babies is born with some form of heart defect. This means that around 40,000 babies each year enter the world with a heart that formed differently during pregnancy.^[1][7][8]

The impact of these conditions varies greatly from child to child. About one in four babies born with a congenital heart defect has what doctors call a “critical” heart defect. These critical cases require surgery or other medical procedures within the first year of life to help the baby survive and thrive.^[8]

Today, more than 2 million people in the United States are living with congenital heart disease. This growing number reflects the tremendous progress medicine has made over recent decades. Where once many children with heart defects did not survive to adulthood, advances in diagnosis and treatment now allow most of these children to grow up and lead meaningful lives.^[7][20]

The disease affects people across all backgrounds and communities. While some types of heart defects may be more common in certain families or ethnic groups, congenital heart disease as a whole does not discriminate based on geography, race, or economic status.

What Causes Congenital Heart Disease

The heart of a developing baby begins to form at the moment of conception and completes its basic structure by eight weeks into pregnancy. Congenital heart defects occur when crucial development steps do not happen at the right time or in the correct sequence during these first eight weeks. This can result in a baby being born with a single blood vessel where two should exist, or with a hole between chambers that should be completely separated.^[9]

In most cases, doctors cannot pinpoint exactly why a particular baby develops a heart defect. The cause often remains unknown, which can be frustrating for families seeking answers. What researchers do understand is that changes in a baby’s genes sometimes cause a heart defect. These genetic changes may be inherited from parents, or they may happen spontaneously during pregnancy without any family history.^[7]

The development of the heart is an incredibly complex process. The organ must transform from a simple tube into a four-chambered pump with multiple valves and blood vessels, all coordinated perfectly to work together. Any interruption in this delicate sequence can lead to structural problems.

Risk Factors for Congenital Heart Disease

While the exact cause often remains unclear, several factors can increase the likelihood that a baby will be born with a heart defect. Understanding these risk factors helps families and healthcare providers monitor pregnancies more carefully and prepare for any needed interventions.

A mother’s health before and during pregnancy plays a significant role. Women who have diabetes before becoming pregnant, or who develop it during the first three months of pregnancy, face higher risks of having a baby with a heart defect. The good news is that carefully controlling blood sugar levels before and during pregnancy can lower this risk considerably. Women with a rare inherited disorder called phenylketonuria (PKU), which affects how the body uses protein, can also reduce their baby’s risk by following a low-protein diet before getting pregnant.^[6]

Infections during pregnancy can also contribute to heart defects. If a woman contracts rubella, also known as German measles, while pregnant, it can affect the developing baby’s heart. This is one reason why vaccination before pregnancy is so important.

Certain substances that a pregnant woman comes into contact with may increase risk. Smoking or breathing in secondhand smoke during pregnancy has been linked to heart defects. Some medications can also pose problems, particularly certain drugs used to treat high blood pressure called ACE inhibitors, and medications containing retinoic acids used for acne treatment. Women who are pregnant or planning to become pregnant should always discuss all medications with their healthcare provider.^[6]

Family history matters as well. If either parent was born with a congenital heart defect, or if a family already has one child with a heart defect, the chance of having another child with a similar condition increases. However, it’s important to note that in most cases, congenital heart defects do not run in families.^[6]

Signs and Symptoms of Congenital Heart Disease

The signs and symptoms of congenital heart disease vary widely depending on the specific type of defect and how severe it is. Some defects are so mild that they cause no noticeable symptoms at all, while others make themselves known immediately after birth or during childhood.

One of the most recognizable signs is cyanosis, which refers to a bluish tint to the skin, lips, and fingernails. This happens when there isn’t enough oxygen circulating in the blood. The blue color can be subtle or quite noticeable, and it often becomes more apparent when a baby is crying or feeding.^[1][6]

Babies with heart defects often struggle during feeding. They may become unusually sleepy or tired while eating, have difficulty breathing, or even sweat during feedings. This happens because eating requires significant energy, and for infants, it is the biggest source of calorie expenditure. When the heart isn’t working efficiently, this already demanding activity becomes even more exhausting.^[11][13]

Doctors may first suspect a heart problem when they hear an unusual sound called a heart murmur while listening to a baby’s or child’s heart with a stethoscope. A heart murmur is an extra sound between heartbeats. Not all murmurs indicate a problem, but they often prompt further testing to rule out a heart defect.^[5]

Breathing difficulties are another common symptom. Children might breathe faster than normal or appear to struggle with each breath. They may also develop swelling in their legs or other parts of the body as fluid builds up. This can signal that the heart is having trouble pumping blood effectively throughout the body.

Some heart defects don’t cause symptoms until later in childhood, adolescence, or even adulthood. This is particularly true for milder defects that allow the heart to function well enough during early years but create problems as the body grows and demands more from the cardiovascular system.^[1]

Prevention of Congenital Heart Disease

While most congenital heart defects cannot be completely prevented because their causes are often unknown, there are important steps that women can take before and during pregnancy to reduce the risk as much as possible.

Taking control of existing health conditions before becoming pregnant is crucial. Women with diabetes should work closely with their healthcare team to achieve good blood sugar control before conception and maintain it throughout pregnancy. Those with conditions like PKU need to follow their prescribed dietary restrictions carefully, especially when planning to become pregnant.^[6]

Avoiding harmful substances during pregnancy protects the developing baby’s heart. This means not smoking and staying away from secondhand smoke. It also means being cautious about medications. Women should review all medications with their doctor before becoming pregnant and avoid taking any drugs not specifically approved for pregnancy. This includes over-the-counter medications and supplements.^[6]

Protecting against infections during pregnancy also helps. Women who are not immune to rubella should be vaccinated before becoming pregnant, as the vaccine cannot be given during pregnancy. Practicing good hygiene and avoiding people who are sick reduces the risk of contracting infections that could affect the baby.

Regular prenatal care allows doctors to monitor the baby’s development and potentially detect heart problems early. Some heart defects can be identified during pregnancy through special ultrasound examinations called fetal echocardiograms. Early detection doesn’t prevent the defect, but it does allow families and medical teams to prepare for any treatments the baby might need immediately after birth.^[8]

After a baby is born, newborn screening for critical heart defects helps identify problems that weren’t detected during pregnancy. This involves a simple bedside test called pulse oximetry, which measures the amount of oxygen in the baby’s blood. Low oxygen levels can signal a critical heart defect that needs immediate attention. This screening has become standard practice in many hospitals because catching these defects early can prevent serious health problems or death.^[8]

How Congenital Heart Disease Affects the Body

To understand how congenital heart defects affect the body, it helps to know what the heart normally does. The heart is a muscular pump divided into four chambers. The right side receives blood that has circulated through the body and pumps it to the lungs to pick up oxygen. The left side receives oxygen-rich blood from the lungs and pumps it out to the rest of the body. Valves between the chambers and at the exits ensure blood flows in the right direction.

Congenital heart defects disrupt this carefully orchestrated flow. The problems can be grouped into several categories based on how they affect blood circulation. Some defects allow too much blood to flow to the lungs. Others prevent enough blood from reaching the lungs to pick up oxygen. Still others block blood from flowing properly to the rest of the body.^[9][17]

When there are holes in the walls separating the heart’s chambers, oxygen-rich blood that should be traveling to the body can leak back into the right side of the heart and recirculate through the lungs. This creates extra work for both the heart and lungs. The heart must pump a larger volume of blood with each beat, and the lungs experience increased pressure as more blood than necessary flows through them. Over time, this extra stress can damage the lungs and cause the heart muscle to enlarge or weaken.^[9]

Defects that restrict blood flow to the lungs have the opposite problem. Without enough blood reaching the lungs to pick up oxygen, the body doesn’t receive adequate oxygen supply. This is what causes the bluish skin color seen in some babies with heart defects. Every cell in the body needs oxygen to function properly, so when oxygen levels are too low, it affects growth, development, and the function of all organs.^[1]

Some defects involve narrowed or blocked valves and blood vessels. When a valve is too narrow, the heart must work much harder to force blood through it. This extra work can cause the heart muscle to thicken as it tries to compensate, similar to how a bicep muscle grows larger with repeated use. However, unlike a bicep, an overly thickened heart doesn’t work better—it becomes less efficient and can eventually fail.^[4]

Complex defects might involve multiple problems occurring together. For example, some babies are born with only one fully developed pumping chamber instead of two, or with the major arteries connected to the wrong chambers. These situations dramatically alter how blood flows through the heart and require specialized treatment approaches.^[4]

The body has remarkable abilities to adapt to these abnormalities, at least initially. Children may grow more slowly than their peers, not because of poor nutrition but because their hearts burn extra calories working harder than normal. Some develop strategies to compensate, like breathing faster to take in more oxygen or eating smaller meals more frequently because feeding is so exhausting.^[9]

Without treatment, many of these adaptations eventually fail as the demands on the heart grow beyond what it can handle. The constant extra work can lead to heart failure, a condition where the heart can no longer pump enough blood to meet the body’s needs. Abnormal heart rhythms can develop as the electrical signals that coordinate heartbeats become disrupted. The lungs can suffer permanent damage from prolonged exposure to excessive blood flow or pressure.