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What Causes Tetralogy of Fallot?

Doctors often don't know what causes tetralogy of Fallot and other congenital heart defects.

Some conditions or factors that occur during pregnancy may raise your risk of having a child who has tetralogy of Fallot. These conditions and factors include:

  • German measles (rubella) and some other viral illnesses
  • Poor nutrition
  • Alcohol use
  • Age (being older than 40)
  • Diabetes

Heredity may play a role in causing tetralogy of Fallot. An adult who has tetralogy of Fallot may be more likely than other people to have a baby with the condition.

Children who have certain genetic disorders, such as Down syndrome and DiGeorge syndrome, often have congenital heart defects, including tetralogy of Fallot.

Researchers continue to search for the causes of tetralogy of Fallot and other congenital heart defects.

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Tetralogy of Fallot Clinical Trials

Clinical trials are research studies that explore whether a medical strategy, treatment, or device is safe and effective for humans. To find clinical trials that are currently underway for Tetralogy of Fallot, visit

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July 01, 2011 Last Updated Icon

The NHLBI updates Health Topics articles on a biennial cycle based on a thorough review of research findings and new literature. The articles also are updated as needed if important new research is published. The date on each Health Topics article reflects when the content was originally posted or last revised.