Birth defects

• Birth defects can cause disabilities and even death.
• Alcohol and drug use while pregnant can cause birth defects.
• Ask your provider what you can do to prevent birth defects.

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About 35,000 infants (1 out of every 125) are born with heart defects each year in the United States (1). The defect may be so slight that the baby appears healthy for many years after birth, or so severe that his life is in immediate danger.

Heart defects are among the most common birth defects and are the leading cause of birth defect-related deaths (2). However, advances in diagnosis and surgical treatment have led to dramatic increases in survival for children with serious heart defects. In the United States, about 1.4 million children and adults live with congenital heart defects today (3). Almost all are able to lead active, productive lives (1).

What is a congenital heart defect?
A congenital heart defect is an abnormality in any part of the heart that is present at birth. Heart defects originate in the early weeks of pregnancy when the heart is forming.

How does the heart work?
The heart is a muscle that pumps blood to the body. It is divided into four hollow parts called chambers. Two chambers are located on the right side of the heart, and two are on the left. Within the heart are four valves (one-way openings) that let the blood go forward and keep it from going back. Blood goes from the heart to the lungs where it picks up oxygen. From the lungs, the blood carrying oxygen, which appears bright red, goes back to the heart. The heart then pumps the oxygen-rich blood through the body by way of arteries. As the oxygen is used up by the body's tissues and organs, the blood becomes dark and returns by way of veins to the heart, where the process starts over again.

How do heart defects affect a child?
Some babies and children with heart defects experience no symptoms. The heart defect may be diagnosed if the health care provider hears an abnormal sound, called a murmur. Children with normal hearts also can have heart murmurs, called innocent or functional murmurs. A provider may suggest tests to rule out a heart defect.

Certain heart defects can cause congestive heart failure.
In this condition, the heart can’t pump adequate blood to the lungs or other parts of the body. It can lead to fluid build-up in the heart, lungs and other parts of the body. An affected child may experience a rapid heartbeat and breathing difficulties, especially during exercise. Infants may experience these difficulties during feeding, sometimes resulting in poor weight gain. Affected infants and children also may have swelling of the legs or abdomen or around the eyes.

Some heart defects result in a pale grayish or bluish coloring of the skin called cyanosis. This usually appears soon after birth or during infancy and should be evaluated immediately by a health care provider. On occasion, cyanosis may be delayed until later in childhood. Cyanosis is a sign of defects that prevent the blood from getting enough oxygen. Children with cyanosis may tire easily. Symptoms, such as shortness of breath and fainting, often worsen when the child exerts himself. Some youngsters may squat frequently to ease their shortness of breath.

What tests are used to diagnose heart defects?
Babies and children who are suspected of having a heart defect are usually referred to a pediatric cardiologist (children’s heart disease specialist). This doctor can do a physical examination and often recommends one or more of the following tests:

• Chest X-ray
• Electrocardiogram, a test that records heart rate patterns
• Echocardiogram, a special form of ultrasound that uses sound waves to take pictures of the heart

All of these tests are painless and noninvasive (nothing enters the child’s body). Some children with heart disease also may need to undergo a procedure called cardiac catheterization. In this procedure, a thin, flexible tube is inserted into the heart after the child is given medications to make him sleepy. This test provides detailed information about the heart and how it is working.

What causes congenital heart defects?
In most cases, scientists do not know what makes a baby's heart develop abnormally. Genetic and environmental factors appear to play roles.

Scientists are making progress in understanding the genetics of heart defects. Since the 1990s, they have identified about 10 gene mutations (changes) that can cause isolated (not accompanied by other birth defects) heart defects (3). For example, a March of Dimes grantee identified a gene that can cause a heart defect called an atrial septal defect (a hole between the upper chambers of the heart), and one that may contribute to hypoplastic left heart syndrome (underdevelopment of the heart’s main pumping chamber) (4, 5).

Environmental factors can contribute to congenital heart defects. Women who contract rubella (German measles) during the first three months of pregnancy have a high risk of having a baby with a heart defect. Other viral infections, such as the flu, also may contribute, as may exposure to certain industrial chemicals (solvents) (2). Some studies suggest that drinking alcohol or using cocaine in pregnancy may increase the risk of heart defects (2).

Certain medications increase the risk. These include (2):

• The acne medication isotretinoin (Accutane and other brand names)
• Thalidomide (approved only for a rare, severe skin disorder, but sometimes used for other conditions)
• Certain anti-seizure medications

Some studies suggest that first-trimester use of trimethoprim-sulfonamide (a combination of antibiotics sometimes used to treat urinary-tract infections) may increase the risk of heart defects (2).

Certain chronic illnesses in the mother, such as diabetes, may contribute to heart defects (2). However, women with diabetes can reduce their risk by making sure their blood sugar levels are well controlled before becoming pregnant.

Heart defects can be part of a wider pattern of birth defects. For example, at least 30 percent of children with chromosomal abnormalities, such as Down syndrome (intellectual disabilities and physical birth defects) and Turner syndrome (short stature and lack of sexual development), have heart defects (3). Children with Down syndrome, Turner syndrome and certain other chromosomal abnormalities should be routinely evaluated for heart defects.

Heart defects also are common in children with a variety of inherited disorders, including Noonan syndrome (short stature, learning disabilities), velocardiofacial syndrome (craniofacial defects and immune deficiencies), Holt-Oram syndrome (limb defects) and Alagille syndrome (liver, skeletal and eye defects) (3).

What are some of the most common heart defects, and how are they treated?

• Patent ductus arteriosus (PDA): Before birth, a large artery (ductus arteriosus) lets the blood bypass the lungs because the fetus gets its oxygen through the placenta. The ductus normally closes soon after birth so that blood can travel to the lungs and pick up oxygen. If it doesn’t close, the baby may develop heart failure. This problem occurs most frequently in premature babies. Treatment with medicine during the early days of life often can close the ductus. If that doesn't work, surgery is needed.
• Septal defect: This is a hole in the wall (septum) that divides the right and left sides of the heart. A hole in the wall between the heart’s two upper chambers is called an atrial septal defect, while a hole between the lower chambers is called a ventricular septal defect. These defects can cause the blood to circulate improperly, so the heart has to work harder. Some atrial septal defects can be repaired without surgery by inserting a thin, flexible tube into the heart and then releasing a device that plugs the hole. A surgeon also can close an atrial or ventricular septal defect by sewing or patching the hole. Small holes may heal by themselves or not need repair at all.
• Coarctation of the aorta: Part of the aorta, the large artery that sends blood from the heart to the rest of the body, may be too narrow for the blood to flow evenly. A surgeon can cut away the narrow part and sew the open ends together, replace the constricted section with man-made material, or patch it with part of a blood vessel taken from elsewhere in the body. Sometimes, this narrowed area can be widened by inflating a balloon on the tip of a catheter (tube) inserted through an artery.
• Heart valve abnormalities: Some babies are born with heart valves that do not close normally or are narrowed or blocked, so blood can’t flow smoothly. Surgeons usually can repair the valves or replace them with man-made ones. Balloons on catheters also are frequently used to fix faulty valves.
• Tetralogy of Fallot: This combination of four heart defects keeps some blood from getting to the lungs. As a result, the blood that is pumped to the body may not have enough oxygen. Affected babies have episodes of cyanosis and may grow poorly. This defect is usually surgically repaired in the early months of life.
• Transposition of the great arteries: Transposition occurs when the positions of the two major arteries leaving the heart are reversed, so that each arises from the wrong pumping chamber. Affected newborns suffer from severe cyanosis due to a lack of oxygen in the blood. Recent surgical advances make it possible to correct this serious defect in the newborn period.
• Hypoplastic left heart syndrome: This combination of defects results in a left ventricle (the heart’s main pumping chamber) that is too small to support life. Without treatment, this defect is usually fatal in the first few weeks of life. However, over the last 25 years, survival rates have dramatically improved with new surgical procedures and, less frequently, heart transplants (6).

At what age do children have surgery to repair heart defects?
Many children who require surgical repair of heart defects now undergo surgery in the first months of life. Until recently, it was often necessary to make temporary repairs and postpone corrective surgery until later in childhood. Now, early corrective surgery often prevents development of additional complications and allows the child to live a normal life.

Following surgery, children should have periodic heart checkups with a cardiologist. Children and adults with certain heart defects, even after surgical repair, remain at increased risk of infection involving the heart and its valves. Parents of children with heart defects and adults with repaired heart defects should discuss with their provider whether they need to take antibiotics before dental visits and other procedures to prevent these infections. Antibiotic treatment is recommended only for those considered at highest risk for infection, including those with man-made heart valves (7).

Is there a prenatal test for congenital heart defects?
Echocardiography can be used before birth to accurately identify many heart defects. If this test shows that a fetus’s heart is beating too fast or too slowly (called an arrhythmia), the mother can be treated with medications that may restore a normal heart rhythm in the fetus. This treatment often prevents fetal heart failure. In other cases, where the heart defect can't be treated before birth, parents and providers can plan the delivery so that the baby can receive necessary evaluation and treatment soon after birth.

Can congenital heart defects be prevented?
Most congenital heart defects cannot be prevented. However, there are some steps a woman can take before and during pregnancy that may help reduce the risk of having a baby with a heart defect:

• Take a multivitamin containing 400 micrograms of folic acid daily, starting before pregnancy. This helps to prevent serious birth defects of the brain and spinal cord and may also help prevent heart defects.
• Go for a preconception visit with her health care provider. At this visit, a woman should be tested for immunity to rubella and be vaccinated if she is not immune. Women with chronic health conditions, such as diabetes and phenylketonuria (PKU), should discuss adjusting their medications and/or eating habits to keep these conditions under control before and during pregnancy.
• Discuss all medications with their provider, even over-the-counter or herbal medicines.
• Avoid people who have the flu or other illnesses with fever.
• Avoid exposure to organic solvents, used in products such as paints, varnishes and degreasing/cleaning agents.

Are heart defects likely to recur in another pregnancy?
Parents who have already had a child with a heart defect do have an increased risk of having other affected children, often with the same heart defect. In many cases, the risk is low. Some heart defects have about a 2 to 3 percent chance of happening again (8). However, the risk may differ, depending on the specific heart defect. If a child’s heart defect is part of a syndrome of other birth defects, the recurrence risk in another pregnancy may be much higher.

Parents who have had a child with a heart defect should consult their pediatric cardiologist and can consult a genetic counselor to find out the risks to any future children. Parents who themselves have a heart defect also are at increased risk of having an affected child and should consider consulting a genetic counselor.

Is pregnancy safe for women with heart defects?
Many women with congenital heart defects can safely become pregnant and have healthy babies. However, women with congenital heart defects always should check with their cardiologist before they become pregnant. Pregnancy can be risky for women with certain types of heart disease (including those with poorly functioning ventricles or high blood pressure in the lungs) (9).

In some cases, the mother’s heart disease or the medications she takes to treat it can affect the fetus, causing poor growth, premature delivery or other problems (9). Some women with heart disease may need careful monitoring by a high-risk obstetrician, as well as their cardiologist, throughout pregnancy.

Does the March of Dimes support research on congenital heart defects?
A number of scientists funded by the March of Dimes are studying genes that may underlie specific heart defects or seeking to identify new genes that may cause heart defects. The goal of this research is to better understand the causes of congenital heart defects, in order to develop ways to prevent them. Grantees also are looking at how environmental factors (such as a form of vitamin A called retinoic acid) may contribute to congenital heart defects. One grantee is seeking to understand why some babies with serious heart defects develop brain injuries, in order to learn how to prevent and treat them.

For additional information on congenital heart defects:

• National Heart, Lung and Blood Institute
• American Heart Association 
• Congenital Heart Information Network
• Velocardiofacial syndrome, U.S. National Institute on Deafness and Other Communication Disorders
• Little Hearts 

References

1. National Heart, Lung and Blood Institute. Congenital Heart Defects. December 2007.
2. Congenital Cardiovascular Defects: Current Knowledge: A Scientific Statement From the American Heart Association Council on Cardiovascular Disease in the Young. Circulation, volume 115, June 12, 2007, pages 2995-3014.
3. Pierpont, M.E., et al. Genetic Basis for Congenital Heart Defects: Current Knowledge: A Scientific Statement From the American Heart Association Congenital Cardiac Defects Committee, Council on Cardiovascular Disease in the Young. Circulation, volume 115, June 12, 2007, pages 3015-3038.
4. Garg, V., et al. GATA4 Mutations Cause Human Congenital Heart Defects and Reveal an Interaction with TBX5. Nature, volume 424, July 24, 2003, pages 443-447.
5. Garg, V., et al. Mutations in NOTCH1 Cause Aortic Valve Disease. Nature, volume 437, September 8, 2005, pages 270-274.
6. Johnston, M.V. Congenital Heart Disease and Brain Injury. New England Journal of Medicine, volume 357, number 19, November 2, 2007, pages 1971-1973.
7. American Heart Association. Congenital Heart Defects. Accessed 3/24/08.
8. Gill, H.K., et al. Patterns of Recurrence of Congenital Heart Disease. Journal of the American College of Cardiology, volume 42, number 5, September 3, 2003, pages 923-929.
9. Uebing, A., et al. Pregnancy and Congenital Heart Disease. British Medical Journal, volume 332, February 18, 2006, pages 401-406.

May 2008