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  • What is tetralogy of Fallot?
    • Tetralogy of Fallot (Pronounced te-tral-uh-jee of Fal-oh ) is a problem with the heart’s structure that is present at birth. This defect changes the normal flow of blood through the heart. Tetralogy of Fallot is a combination of four defects:
      * ventricular septal defect - A hole in the wall between the ventricles (two lower chambers of the heart).
      * pulmonary stenosis - A narrowing of the tube that carries blood from the heart to the lungs.
      * The aorta (the tube that carries oxygen-rich blood to the body) grows from both ventricles, rather than from the left ventricle only.
      * right ventricular hypertrophy - A thickened muscular wall of the right ventricle.

      The left ventricle houses blood that is rich in blood and is pumped throughout the body. The right ventricle houses the blood that is low in oxygen. With Tetralogy of Fallot, the blood between the two ventricles is mixed together, and blood that is low in oxygen is pumped through the body. As a result, the body does not get enough oxygen to function normally. Infants and young children with tetralogy of Fallot often have blue- or purplish-looking skin color, called cyanosis, because of this lack of oxygen.

      At birth, infants might not have blue-looking skin, but later might develop sudden episodes (called "Tet spells") of bluish skin during crying or feeding.

      CDC estimates each year that about 1,575 babies in the United States are born with tetralogy of Fallot. In other words, about 4 out of every 10,000 babies born in the United States each year are born with tetralogy of Fallot.

  • What problems do people with tetralogy of Fallot have?
    • Many babies with this condition will have to have surgery to correct it. Babies who have surgery usually do well. Unfortunately, without surgery, death usually occurs before the person reaches 20 years of age.

      People who have continuing, severe leakage of the pulmonary valve might need to have the valve replaced. In addition, babies should have a follow-up visit with a cardiologist to monitor for life-threatening arrhythmias (irregular heart rhythms).

      Following are just a few of the issues that people with tetralogy of Fallot might have to face.
      * Children with this condition might need to limit their physical activity, especially in competitive sports.
      * People with tetralogy of Fallot are at increased risk for developing endocarditis (an infection of the inner layer of the heart).
      * People with repaired tetralogy of Fallot have a higher risk of heart rhythm disturbances, called arrhythmias. Sometimes these can cause dizziness or fainting. Medicine or medical procedures might be needed to address these issues.
      * People with tetralogy of Fallot can have delayed growth and development.
      * People with tetralogy of Fallot can have seizures during periods when insufficient oxygen is being carried in the blood.

  • What causes tetralogy of Fallot?
    • A specific cause for tetralogy of Fallot is unknown. Indeed, scientists generally agree that multiple causes seem to be involved. For example, mothers who experience rubella or other viral illnesses during pregnancy have a higher risk of having a baby with tetralogy of Fallot. In addition, scientists have found that mothers with poor nutrition, a history of alcohol use, or diabetes, or who are older than 40 years of age might have a higher risk for having a baby with tetralogy of Fallot.

      CDC has worked with many other researchers to study risk factors that can increase the chance of having a baby with tetralogy of Fallot, as well as outcomes of babies with the defect. Following are examples of some relevant results from that research:
      * The rate of tetralogy of Fallot has been increasing from over time.
      * The environment, specifically carbon monoxide, might be a risk factor for having a baby with tetralogy of Fallot, although more research is needed.
      * There is a higher risk for tetralogy of Fallot among White babies than babies of other races or ethnicities.
      * No strong link exists between caffeine use by a mother and risk for tetralogy of Fallot.

  • Can tetralogy of Fallot be prevented?
    • There is no known way to prevent the defect, but some of the problems later in life that are associated with having it can be prevented or improved if the defect is found early.

      Even so, mothers can take steps before and during pregnancy to have a healthy pregnancy. Such steps include taking a daily multivitamin with folic acid (400 micrograms), not smoking, and not drinking alcohol during pregnancy.

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Last Revised: January 28, 2014


Data Query

Tetralogy of Fallot Data Query
Access the tetralogy of Fallot data (without anencephaly) in the WI EPHT online database. Review the Data Details below to learn about interpreting the data.

The WI EPHT online data has data about other birth defects:
Cleft Lip with or without Cleft Palate
Cleft Palate without Cleft Lip
Down Syndrome (Trisomy 21)
Hypoplastic Left Heart Syndrome
Spina Bifida
Transposition of the Great Arteries
Lower Limb Deficiencies
Upper Limb Deficiencies

Data Details

What is the data source?

The website provides data from the Wisconsin Birth Defects Registry, which is maintained by the Birth Defect Prevention and Surveillance program, Wisconsin Department of Health Services.

How does WI EPHT measure birth defects?

The WI EPHT website includes the following measures:

  • Prevalence rate of live births by geography
  • Number of birth defects by geography

What are some considerations for interpreting the data?

While significant effort is made to ensure the accuracy and completeness of the data, there are limitations that are listed below:

  • The Wisconsin Birth Defects Registry does not currently receive reports from all providers in the state. Thus, the numbers presented here represent only a subset of the actual cases.
  • Reporters have up to two years to provide data to the registry, so some cases from the most recent years may not yet be included in the registry.

There are many factors that can contribute to a disease and should be considered when interpreting the data. Some of these include:

  • Demographics, e.g., race, gender, age
  • Socioeconomic Status, e.g., income level, education
  • Geographic, e.g., urban vs. rural
  • Changes in the medical field, e.g., diagnosis patterns, reporting requirements