What is a hypercoagulable state?
A hypercoagulable state occurs when there is an abnormally high tendency for the blood to thicken and clot. This can be the result of environmental factors (e.g., hormones, illness including surgery, or cancer) or because of inherited blood clotting problems. Blood clotting problems like these are more likely to increase your risk of blood clots in the deep veins of the legs (deep vein thrombosis or DVT) than clots in the arteries that can cause a heart attack. A blood clot or thrombus in the veins of the legs can break off and travel through the bloodstream to block an artery in the lungs causing the life-threatening condition, pulmonary embolism.
What causes blood clotting problems?
There are several causes for blood clotting problems. You are more prone to developing blood clots after surgery (especially hip or knee), if you are immobilized for more than 4 days, or as a result of injuries from a severe accident. Cancer can lead to a hypercoagulable state: 1% to 15% of cancer patients develop blood clots in their veins.1
Hormones, including the estrogen found in hormone therapy and birth control pills, can increase your risk of developing blood clots. During pregnancy, levels of blood clotting proteins rise and blood thinning enzymes fall. In most cases, these changes are not a cause for concern. Some women inherit blood clotting problems that increase their risk for miscarriage. These inherited blood clotting problems also put you at a higher risk of blood clots or DVT when you take oral contraceptives or hormone therapy.
What is Factor V Leiden?
Some people have a higher risk of blood clotting problems because they are born with mutations (mistakes) in the genes for blood clotting proteins. The most common inherited blood clotting problem is called Factor V Leiden (FVL), so-called because it affects the Factor V (five) clotting protein. FVL occurs in about 5% of white men and women; rates are lower for Hispanics and it is rare in people of Asian or African descent.2
Women who have one defective FVL gene have a 30-fold higher risk of developing blood clots while using birth control pills,3 a 15-fold higher risk with postmenopausal hormone therapy, and a 7-fold higher risk during pregnancy compared with women without this mutation.4 While their risks are much higher relative to women without the mutation, the actual risk remains quite low.5 Women who carry two abnormal FVL genes have an even greater risk of developing blood clots.6, 7 It is likely that these women will experience at least one blood clotting event during their lifetime.6