There are two things to think about when considering your risk: the risk of having a venous thrombosis (a blood clot) and the risk of having thrombophilia (a predisposition for blood clotting).

Everyone is at risk for having a blood clot during their lifetime. The question is, how high is the risk for you at this time? Venous thrombosis isusually caused by a combination of factors.

Finding out whether you have an inherited thrombophilia and learning about other risk factors can help you determine your risk for venous thrombosis. Once you know your risk, you can make appropriate decisions about health care and lifestyle.

Step 1: Your Age-Related Risks
Step 2: Your Family and Medical History
Step 3: Your Lifestyle and Triggering Events
Step 4: Your Genetic Risks

Step 1: Your Age-Related Risks

First, start by identifying your age-related risk using the chart below. It is estimated that the age-related risks for the prothrombin mutation are approximately half of the risks for factor V Leiden, but exact data is not available.

Step 2: Your Family and Medical History

Next, ask yourself whether any of the following questions apply to you.

• Do you have a personal history of a blood clot in the veins — venous thrombosis, DVT, or PE?
  • About 25 percent (1 in 4) people who have had a blood clot in the veins have an inherited thrombophilia.
• A family history of blood clots in the veins?
  • As high as 63 percent of families with blood clots in more than one family member have an inherited thrombophilia.
• A known inherited thrombophilia mutation — factor V Leiden or prothrombin — in the family?
  • If your parent, sibling, or child has an inherited thrombophilia, you have a 50 percent (1 in 2) chance of having the same genetic risk.
  • If your uncle, aunt, grandparent, niece, or nephew has an inherited thrombophilia, you have a 25 percent (1 in 4) chance of having the same genetic risk.
  • The more distant the family member, the more your risk decreases.
• Pregnancy complications such as multiple miscarriages, preeclampsia, placental abruption, stillbirth, or a pregnancy that did not grow as expected (IUGR)?
  • Women who have an inherited thrombophilia are at increased risk for miscarriage, stillbirth, and these pregnancy-related complications.
• An active cancer or another health condition?
  • Everyone who has an active cancer has a 1 in 25 risk of having a blood clot. That risk increases when a person has an inherited thrombophilia.

Step 3: Your Lifestyle and Triggering Events

Are you concerned about any of the following? Knowing whether you have an inherited risk can change the way you evaluate these risks.

• Taking birth control pills?
  • All women have a risk of having a blood clot while taking the pill. For a woman with the factor V Leiden mutation, the risk increases 30 to 35 times. For women with more than one mutation, the risk is 100 times higher.
• Taking hormone replacement therapy?
  • All women have a risk of having a blood clot while taking HRT. For a woman with a factor V Leiden mutation, the risk increases 13 to 15 times. For women with two mutations, the risk is even higher.
• Being or becoming pregnant?
  • Blood clots are the major cause of maternal death during pregnancy.
  • All pregnant women have a risk of having a blood clot. For a pregnant woman with a factor V Leiden mutation, the risk increases 7 to 16 times. For women with two mutations, the risk is 40 times higher.
• Having surgery?
  • There is always a risk of having a blood clot during surgery or recovery. For a person with a factor V Leiden mutation the risk increases about 20 times.
• Taking long flights or car trips?
  • A person with an inherited thrombophilia has a greater risk of developing a blood clot during long distance travel (3 hours or more), but the exact amount of risk is unclear.
• Having other lifestyle risk factors like immobility, obesity, smoking?
  • Living a sedentary lifestyle, being obese, and smoking all contribute to the risk of developing cardiovascular disease including having a blood clot. It is not clear how much these risk factors increase the risk of blood clots.

Step 4: Your Genetic Risk

Understanding whether you are at risk for having thrombophilia is a complex process. To determine if you are at risk for carrying factor V Leiden or the prothrombin mutation, take our Free Risk Assessment for Thrombophilia.

The questionnaire will ask you more about your personal and family medical history, lifestyle, and triggering events. It will also provide more detailed information on why these questions are important.

The Risk Assessment will give you a personalized Benefit Index, based on medical guidelines, that explains whether genetic testing would be of benefit to you and why.