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Hereditary thrombophilia is a condition that can be passed from parent to child and can sometimes cause blood clots to form inside veins when they shouldn’t. This can lead to health problems and, in some cases, be life-threatening.

More about hereditary thrombophilia

People with hereditary thrombophilia have a higher-than-typical chance of developing a potentially dangerous blood clot. Normally when people get injured, their blood forms clots—clumps of blood that plug up the wound. The clots keep them from losing too much blood.

But sometimes clots form inside veins when they are not needed. These clots can be dangerous—especially if they travel to another part of the body. When that happens, the clot can block blood flow to tissues or organs and cause health problems. (These clots can happen to anyone, but they’re more likely in people with thrombophilia.)

The most common type of potentially dangerous clots is called deep vein thrombosis (DVT). These clots typically form in a leg but sometimes form in an arm or elsewhere. They may cause the skin to be swollen, painful, warm, and reddish and cause pain in the calf or inner thigh.

One of the dangers of this type of clot is that it might break loose and travel through the blood to the lungs. If that happens, it can cause a pulmonary embolism, which can slow down the flow of blood to the lungs. This can cause difficulty breathing, chest pain, rapid heartbeat, or fainting. Pulmonary embolisms can be life-threatening and require immediate medical attention.

DNA differences linked to hereditary thrombophilia are most common in people of European descent, though they can be found in other populations as well.

Why is it important to know about hereditary thrombophilia?

Having hereditary thrombophilia does not mean a person will develop a serious blood clot, just that the chances that they will do so are higher than typical.

And there are actions people with hereditary thrombophilia can take to lower their chances of potentially dangerous clots:

  • Be aware of certain situations that can increase your chances of clots. Tell a healthcare provider about your result before any of these medical conditions or procedures, all of which can increase the chances of clots:
    • Pregnancy
    • Surgery
    • Being in a cast
    • Being on bed rest
    • Chemotherapy
    • Hormone replacement therapy for menopause
  • Don’t smoke. Smoking can affect how well your blood circulates through your body and increase the chances of clots.
  • Maintain a healthy weight. Try to get more exercise to keep your body active and your blood flowing normally. This can also lead to weight loss, which can reduce the chance of abnormal blood clots.
  • Walk around during long flights or car rides. Not moving your legs for long periods of time can increase your chances of blood clots. Occasional walks down the plane aisle or getting out of the car to walk every few hours may help.
  • Discuss birth control options with a healthcare provider. Methods that include estrogen, such as birth control pills, can increase the chances of blood clots in women* with thrombophilia.

How is hereditary thrombophilia passed down?

In almost all cases, people inherit DNA differences linked to hereditary thrombophilia from one of their biological parents. The two most common DNA differences linked to hereditary thrombophilia are found in two genes: F2 and F5.

The DNA differences people can have that are linked to thrombophilia include:

  • a DNA difference in the F2 gene
  • a DNA difference in the F5 gene
  • a pair of DNA differences: one in the F2 gene and one in the F5 gene
  • two DNA differences: both differences in either the F2 or the F5 gene

If someone has one DNA difference linked to hereditary thrombophilia (either in their F2 or F5 gene), it means they have at least one parent who has hereditary thrombophilia too. It also means their brothers and sisters have a 1 in 2 chance of having it—and so does each of their children.

Here is how the inheritance works in most cases: A person has two copies of most of their genes, one from each of their parents. To have hereditary thrombophilia, they only need to inherit a hereditary thrombophilia DNA difference from one of their parents. If they inherit a hereditary thrombophilia DNA difference from both of their parents, they have an even higher chance of developing an abnormal blood clot.

What does the test offered through AncestryHealth® look at?

The test offered through AncestryHealth® looks for specific DNA differences in the F2 and F5 genes that can cause hereditary thrombophilia.

What do these genes do? Genes have the instructions for making proteins. Proteins are the molecular machines that get things done in the body.

The F5 and F2 genes both make proteins that are part of the coagulation system. This is the system that helps your blood clot at the right time, such as when you get an injury. Certain DNA differences in these genes can lead to too much of these clotting proteins, which can make abnormal blood clots more likely to happen.


*Assigned sex at birth


AncestryHealth® includes laboratory tests developed and performed by an independent CLIA-certified laboratory partner, and with oversight from an independent clinician network of board-certified physicians and genetic counselors. The test results are not diagnostic and do not determine your overall chance of developing a disease or health condition. The tests are not cleared or approved by the U.S. Food and Drug Administration. You should consult a healthcare provider before taking any action based on AncestryHealth® reports, including before making any treatment, dietary, or lifestyle changes. AncestryHealth® is not currently available in New York, New Jersey, or Rhode Island.


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