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Environmental Public Health Tracking: Tetralogy of Fallot Data

A birth defect is a problem that happens while the baby is developing in the mother's body. Most birth defects happen during the first three months of pregnancy. A birth defect may affect how the body looks, works, or both.

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Tetralogy of Fallot is one type of birth defect. Review the FAQs below for more information about tetralogy of Fallot.

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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.
  • Aorta growth defect. 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.

Researchers estimate about 1,660 babies in the United States are born with tetralogy of Fallot each year. In other words, about 1 out of every 2,518 babies born in the United States are born with tetralogy of Fallot each year.*

*Parker SE, Mai CT, Canfield MA, et al; for the National Birth Defects Prevention Network. "Updated national birth prevalence estimates for selected birth defects in the United States, 2004-2006." Birth Defects Res A Clin Mol Teratol. 2010;88:1008-16.

A specific cause for tetralogy of Fallot is unknown. Visit the CDC's (Center for Disease Control and Prevention) Facts about Tetralogy of Fallot page to learn more about causes and risk factors.

There is no known way to prevent the defect, but some of the problems later in life can be prevented or improved if the defect is found early. 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. Learn more about prevention and treatment on the CDC's Facts about Tetralogy of Fallot page.

Last revised January 5, 2023