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What You Need To Know About Factor V Leiden — A Blood Clotting Condition That Can Cause Miscarriages

Factor V Leiden thrombophilia is an inherited blood clotting disorder that can lead to blood clots in the legs, lungs, or other parts of the body. 

Medical term: Thrombophilia is a condition where blood is prone to clotting, even if you're not injured.

"The factor V Leiden mutation is the most common inherited risk factor for abnormal blood clotting in the United States," says Mary Jacobson, MD, and chief medical director at Alpha, an online medical platform for women. "However, it is estimated that 95% of people with Factor V Leiden never develop a clot."

Here's what you should know about factor V Leiden including risk factors, symptoms, diagnosis, and treatment.

What is the V factor?

Factor V is a protein, also known as a clotting or coagulation factor, that's needed for blood to clot properly. Everyone has the factor V protein, but some have a mutated version, causing factor V Leiden (FVL) — a condition named for the Dutch city, Leiden, where it was first discovered in 1994.

Important: Factor V Leiden is due to a specific mutation. There are other genetic mutations that can also cause clotting and bleeding conditions.

Having the factor V gene mutation makes it harder for your body to break up a clot once it's formed, causing hypercoagulability or thrombophilia. This can be a potential risk for life-threatening blockages in your blood.

People can either have one or two copies of the mutated factor V gene, which determines the likelihood of complications. 

"Inheriting one copy slightly increases your risk of developing blood clots. Inheriting two copies — one from each parent — significantly increases your risk of developing blood clots," says Jacobson.

Fast stat: Between 3% and 8% of the Caucasians in the US and Europe carry one copy of the mutated gene. Whereas, only about 0.02% of people have two copies of the mutation. 

Symptoms

"The first indication that you have the disorder may be the development of an abnormal blood clot," says Jacobson. 

While some individuals with FVL may never develop thrombosis, others may experience recurrent thrombosis before the age of 30.

According to the American Society of Hematology, blood clots may show up in other places in the body, including: 

Heart. If a blood clot forms in your heart or lungs, you may experience chest pain, upper body discomfort (in your back, neck, jaw, or arms), and shortness of breath.  

Brain. When a blood clot appears in the brain, it's known as a stroke. If this happens you may feel weakness in your face, arms, or legs, have trouble speaking or seeing, experience a sudden headache or feel dizzy. 

Arm or leg. A blood clot in the arm or leg may cause swelling or tenderness and the pain may be sudden or gradual.

Abdomen. Abdominal blood clots may cause severe abdominal pain, vomiting, diarrhea, or bloody stools. 

 Complications of factor V Potential complications:

Deep vein thrombosis (DVT). DVT occurs when a blood clot forms in one or more of the "deep veins" in the body. Though DVT can affect any part of the body, it typically occurs in the legs and can cause pain or swelling. 

Pulmonary Embolism (PE). PE is when a blood clot detaches itself from where it formed (usually in the legs) and travels through the bloodstream and into the lungs causing a blockage of blood flow to the lungs. Common symptoms of PE include shortness of breath, cough, or chest pain. 

When these conditions occur at the same time, it's referred to as venous thromboembolism or VTE. 

If you have FVL, you may experience one or more of the following: 

Developing DVT or PE before the age of 50 

Recurrent DVT or PE 

Blood clots in the brain or liver 

Having DVT or PE during or following pregnancy 

A history of unexplained pregnancy loss in the second or third trimester 

Risk factors 

If one or more people in your family are diagnosed with FVL, you should consult your doctor. 

"Determining which patients have risk factors for a thrombophilia begins with a detailed history," says Jacobson. "Pregnancy, use of estrogen-containing medications, and gynecologic surgery combined with a factor V Leiden mutation markedly increase the risk of blood clots in the lungs which can be fatal."  

"Testing for this mutation is nearly always done when a patient has a blood clot or certain pregnancy complications, including multiple first-trimester miscarriages, a miscarriage for unknown reasons after 10 weeks of pregnancy, stillbirth, unexplained severe preeclampsia, placental abruption, or a fetus with severe growth restriction," says Kate White, MD, and associate professor of obstetrics and gynecology at Boston University School of Medicine.

Diagnosis 

Although FVL may seem like a complicated disorder, it's easy to diagnose. Your doctor can confirm that you have FVL using two blood tests — factor V Leiden mutation analysis and Prothrombin 20210. 

Each test is performed at the same time to determine whether or not the factor V mutation is present and to see if you have one or two copies of the mutated gene. 

Your doctor may perform other tests to rule out additional factors, like lupus, that may be contributing to excessive clotting. 

Treatment

You can't treat the factor v mutation itself. However, your doctor may recommend that you start taking blood thinners, depending on your medical history and the severity of your symptoms. 

"Patients with factor V Leiden may require medications like blood thinners and more intensive monitoring in pregnancy and preoperatively to reduce the risk of maternal morbidity and mortality," says Jacobson. 

Although FVL cannot be prevented, there are a few things you can do to lower your risk of developing DVT or PE, including: 

Exercising regularly 

Maintaining a healthy weight 

Move around when traveling by plane, train, or vehicle (especially if the trip is four hours or longer)

Stop at least once every two hours if you plan on taking a long road trip 

Wearing compression stockings 

"Since there's no cure for these genetic mutations, the goal is to lower your chance of having risky blood clots while still letting your body make the clots that it truly needs," Jacobson says. 

Insider's takeaway 

Factor V Leiden is an inherited gene mutation that may increase your chance of developing abnormal blood clots. 

If you have a family history of blood clots, you should consider being tested for the FVL mutation — especially if you plan on becoming pregnant. 

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