Family history matters: Preventing thrombosis across generations

May 29, 2025

Blood clots can run in families, making it critical to understand your family health history.

Venous thromboembolism (VTE), which includes deep vein thrombosis (DVT) and pulmonary embolism (PE), affects millions of people each year. While many factors contribute to blood clot formation, genetic predisposition can play a role to an individual’s risk.

The International Society on Thrombosis and Haemostasis (ISTH), which leads the World Thrombosis Day campaign, emphasizes that certain inherited clotting disorders can dramatically increase thrombosis risk. Factor V Leiden, one of the most common inherited clotting disorders, affects approximately 3-8% of people with European ancestry, but it varies significantly across different populations worldwide.

For families concerned about their thrombosis risk, the National Blood Clot Alliance (NBCA) in the United States recommends creating a comprehensive three-generation family health history that includes all known blood clot events, their circumstances and ages of occurrence.

Ann Marie O’Neill, founder of Thrombosis Ireland, suggests specific questions families should explore.

“Ask relatives if anyone has experienced unexplained leg swelling, pain or chest symptoms that required hospitalization,” she said. “Many historical blood clots may have been diagnosed under different terminology.”

Here are some actionable steps for tracking family thrombosis risk:

  • Document all known blood clot events in your extended family, including the specific diagnosis (DVT or PE), age at occurrence and triggering circumstances such as surgery, pregnancy and/or cancer.
  • Share this information with all healthcare providers, especially before situations that increase clot risk like surgery, hospitalization or pregnancy. This documentation should be updated regularly and distributed to family members.
  • Learn to recognize warning signs of blood clots. For DVT, signs and symptoms can include leg pain, swelling, warmth and/or redness. PE symptoms can include sudden shortness of breath, chest pain and/or rapid heartbeat.
  • Consider genetic counseling and testing if you have a strong family history of unexplained blood clots. Genetic testing can identify specific inherited clotting disorders that allows for personalized prevention strategies.

It is important that families with known genetic clotting disorders establish a communication plan to ensure all members understand their risk and appropriate preventive measures.

For families with identified clotting disorders, prevention strategies might include avoiding estrogen-containing contraceptives, using compression stockings during high-risk periods like long flights and receiving prophylactic anticoagulation during hospitalizations.

Healthcare providers can offer specialized guidance based on specific genetic findings, including recommendations for testing other family members who may share the same genetic risk factors. Learn more at www.worldthrombosisday.org.

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