Venous Thromboembolism - Risk Factors - Risk Factors

Risk factors for VTE include a history of a previous VTE event; surgery; medical conditions such as cancer or spinal cord injury; pregnancy; paralysis or long periods of immobilization; specific genes; and certain circumstances related to age, race, and sex. In most cases of VTE, there is more than one risk factor involved. The more risk factors you have, the greater the chance you have of developing VTE.

Read Life After for information about the risk of repeat VTE events.

Surgery

Knee and hip replacement surgery, in particular, carry a high risk for VTE, as does peripheral and coronary artery bypass surgery, surgery to remove cancer, neurosurgery, abdominal surgery, and other major operations. Clotting is one of the body\u2019s natural ways to heal the damage to your blood vessels from surgery. While you wear a cast or stay in bed to heal, your venous circulation slows because you stop moving as much as usual. This lack of movement increases the risk of blood clotting.

The risk of developing VTE is highest in the first three months after surgery and decreases with time. Ask your medical team about prevention strategies if you are scheduled for major surgery.

Other medical conditions

Certain medical conditions can increase your risk of developing a DVT. Some conditions are more closely linked to developing VTE than others and include the following:

Spinal cord injury. In addition to damaging veins deep in your body, spinal cord injury may cause paralysis, which can reduce blood flow and raise your risk of VTE. The risk is highest in the first weeks after the injury.
A broken hip or leg bone or other trauma.
Cancers such as advanced brain, breast, colon, and pancreatic cancer. Cancer chemotherapy, surgical treatment, and placement of a central venous catheter\u2014a tube inserted into a vein to deliver chemotherapy treatment or other medicine\u2014all increase the risk of VTE. Some cancers release substances that can make it easier for blood to clot. Some cancerous tumors may directly block blood flow by pressing on a vein. A central venous catheter increases the risk for VTE in arm veins, especially in children.
Heart conditions such as heart attack or congestive heart failure.
Stroke
Obesity
Varicose veins. Most varicose veins do not cause problems, but large, untreated varicose veins can lead to VTE.
Infections, such as SARS-CoV-2, the virus responsible for COVID-19. Watch our video to learn more about how COVID-19 can lead to a blood clot in the lungs or deep veins, usually in the legs.\u201d Additionally, we offer information and resources on how we are working hard to support necessary COVID-19 research.
Sickle cell disease. This condition makes the blood clot more easily and can be a risk factor for VTE.

Hormone-based medicines

Women who take birth control pills or get hormone therapy have an increased risk of clotting. Some medicines appear to put people at a higher risk than other medicines do, and the risk tends to be highest in the first few months after starting to take them. If you have other risk factors in addition to taking hormone-based medicines, keep in mind that risk for blood clots may be even higher.

Pregnancy and giving birth

Women are at higher risk for VTE during the first six weeks after giving birth to a baby. The risk is also somewhat higher than usual during pregnancy. This may be due to hormones or other factors in the blood, changes in the way blood flows through your veins, or damage to your blood vessels during delivery. If you are required to be on bed rest while you are pregnant, the lack of movement can reduce blood flow through your veins. Surgery for a cesarean delivery may also increase your risk.

Not moving for long periods

Being still slows blood flow through the veins in your arms and legs, raising your risk of deep vein thrombosis. Especially when combined with other risk factors, not moving for long periods of time\u2014such as when on bed rest in a nursing home or hospital setting, when you have a cast, or during a long flight\u2014can increase your risk. Slower blood flow can create a low-oxygen environment that makes it easier for clots to form or trap blood in places such as the veins in the legs where they have a tougher time breaking up.

Age

VTE can occur at any age, but your risk increases as you age. After age 40, the risk of VTE almost doubles every 10 years.

Family history and genetics

Heredity can affect your chances of developing VTE. Researchers have found dozens of genetic changes that can increase your risk of VTE. Some changes make your blood more likely to clot. If your parents have these genetic changes, you may have inherited them. Studies show that the risk of VTE among siblings of someone who has had VTE is more than double the risk among the general population.

Factor V Leiden is the most common known genetic risk factor for VTE. What is Factor V Leiden?

Race or ethnicity

Studies suggest that the frequency and severity of VTE may vary by a person\u2019s race and ethnicity. In the United States, African Americans have the highest rates of VTE. VTE is less common among Asian Americans and Pacific Islanders. Recent findings have revealed new genetic factors influencing a person\u2019s risk for VTE, and those appear to be more common among African Americans.

Sex

Women in their childbearing years are more likely to develop VTE than men of the same age. After menopause, women\u2019s risk is lower than men\u2019s.