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What Is Factor V Leiden?

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by Amy Spangler
July 17, 2009

I am pregnant and someone asked me if I was going to be tested for Factor V Leiden. What is this and do all mothers get tested for it?

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Factor V Leiden is not a disease, but an inherited disorder involving a genetic mutation of the factor V (F5) gene. The F5 gene plays an important role in controlling bleeding. Factor V Leiden gets its name from the Netherlands city (Leiden) where the mutant gene was first identified.

When an injury with bleeding occurs, a protein (coagulation factor V) made by the F5 gene controls the bleeding by forming a clot. Activated protein C keeps the clot from getting too big. In individuals with factor V Leiden, activated protein C is unable to inactivate the coagulation factor, so the clotting process continues unchecked, increasing the risk for abnormal clots such as deep vein thrombosis (a blood clot in a major vein) and pulmonary embolism (a blood clot in the lungs). Factor V Leiden can also increase the risk of miscarriage and complications of pregnancy such as stillbirth and the blood clots in the placenta and umbilical cord.

Despite these risks, most people with factor V Leiden never develop abnormal clots, and most women with factor V Leiden have normal pregnancies. Nonetheless, if you have a family history of factor V Leiden and plan to get pregnant, you should be tested. Knowing that you have factor V Leiden will help your health care provider ensure that you have a healthy pregnancy.

Factor V Leiden is among the more common genetic disorders affecting 3–8 percent of Caucasians in the United States and Europe. Some researchers have suggested that all women be screened for factor V Leiden before taking oral contraceptives (birth control pills) or getting pregnant. Those opposed to universal screening argue that it would deny oral contraceptives to a large group of women and prevent only a small number of deaths due to blood clots. Moreover, the risk of fatal bleeding during pregnancy from prophylactic anticoagulation therapy (treatment to prevent blood clots) is likely greater than the risk of death due to blood clots.

Factor V Leiden should not be confused with factor V deficiency. Factor V deficiency is an inherited disorder characterized by low levels of clotting factor V. Individuals with factor V deficiency have an increased risk for excessive bleeding. Fortunately, factor V deficiency is extremely rare occurring in one in one million.

Linda Addotta

I was diagnosed with Factor V late in life. It was found by accident because one of my daughters were having problems with a pregnancy. I had four successful pregnancy myself. Not knowing which of us had Factor V both my husband and myself were tested by our family doctor. My question is I was just told I have Factor V, but they didn’t say if it was Factor V deficiency or Factor V Leiden. Will the doctor have the answer on the results from the blood test or will I need further testing to determine which I have?
Amy Spangler

I found the following website http://www.fvleiden.org/ask/31.html helpful in understanding test results. It’s important that you need to ask your doctor which test was done and what the results showed. Factor V Leiden and Factor V deficiency are very different. It is unlikely that you have Factor V deficiency given that it is quite rare.
http://MSN SUE

My daughter was informed by her perinatal doctor that she has Leiden V factor which was documented in medical records from her emergency C-section for her 2nd child.

At 26 weeks into pregnancy, my daughter has just given birth to her third child – a stillborn baby boy. Needless to say, she’s quite depressed. Her first child was a preemie baby boy due to my daughter developing preeclampsia at 25 weeks and he weighed 1 lb. 10 oz. Today he is a thriving 5 year old attending kindergarten, thanks to therapy, a shunt, and now medicine for ADHD. Her second little boy who is 3 years old, was born at 30 weeks weighing 3 lb. 9 oz. due to a detached placenta. He has cerebral palsy which affected his motor skills, and he cannot walk. He receiving PT, OT and Speech, and has just undergone ligament surgery.
http://MSN SUE

My daughter was never told about her having the Leiden V factor. And now, after all these pregnancies ending in turmoil and despair, we would like some advice for her and if she should still try to have anymore children. She is only 25 years old, and has never really been able to have a normal pregnancy and have her baby with her upon delivery, etc. Should she go to see her perinatal doctor about discussing being able to have a normal pregnancy, and if this Leiden V factor has been causing all her pregnancy problems, as well as should she see a hematologist, etc. Please advise.
http://www.babygooroo.com Amy Spangler

Factor V Leiden may or may not have played a role in your daughter’s previous pregnancies. But given her previous experiences I would suggest that she ask her doctor to recommend a maternal-fetal specialist who cares exclusively for women who have had a pattern of giving birth prematurely. Hopefully a specialist can determine the likely cause or causes of the previous preterm births and advise your daughter of the likelihood of her having a similar experience with future pregnancies.
Summer

I am 30 weeks pregnant with my 11th pregnancy and have heterozygous factor V leiden and MTHFR. I have a 7 yr old with a heart defect and a healthy 3 yr old, both of which I had via c-section in the 38th week due to increased risks of clotting closer to the end of pregnancy. The hospitals in my area are really pushing to have all deliveries if possible after 39 weeks. This concerns me because I have had so many late losses and I have 2 friends with this clotting disorder lose their babies at 39 weeks. Do you know if it is standard or safer practice to deliver in the 38th week, or if this is a change in practice over the last couple of yeas? Thanks.
http://www.babygooroo.com Amy Spangler

Unfortunately, I am not an expert on factor V leiden or MTFHR (Methylene-Tetra-Hydro-Folate-Reductase). According to the Thrombophilia Awareness Project, “Almost half of the population is “MTHFR hetero” — it is nothing abnormal. The heterozygous MTHFR mutation (= 1 “abnormal” gene) does not lead to increased homocysteine levels. It is the homozygous MTHFR mutation (2 “abnormal” genes) that is associated with higher homocysteine levels. However, it is the fasting homocysteine level that counts, independent of whether the patient has the MTHFR mutation or not. If an individual’s fasting homocysteine level is normal, there is no need for vitamin B or folate therapy – even if the patient has the homozygous MTHFR mutation.”

Individuals with the homozygous form of MTHFR (Methylene-Tetra-Hydro-Folate-Reductase) are at increased risk for clotting problems. So given your pregnancy history, I am assuming you have the homozygous form of MTHFR. I urge you to talk with your doctor about your concerns. And, if necessary, get a second opinion. Hopefully others with the same condition will share their experience.
http://lempskies.blogspot.com Remembering Baby Hope

I like that this post mentions the risk of fatal bleeding from anticoagulation therapy.

I’ve had 3 live, uncomplicated births and 3 miscarriages (2 of which were 2nd trimester) and I recently found out I am heterozygous for Factor V Leiden mutation. The standard treatment for someone like me is Lovenox injections. But when reading material on the Lovenox site I found this statement:

“Human Data – There are no adequate and well-controlled studies in pregnant women.
A retrospective study reviewed the records of 604 women who used enoxaparin (Lovenox) during pregnancy. A total of 624 pregnancies resulted in 693 live births. There were 72 hemorrhagic events (11 serious) in 63 women. There were 14 cases of neonatal hemorrhage. ”

So essentially there is about a 10% chance the mother on Lovenox will hemorrhage.

My mother-in-law suffered an almost fatal brain hemorrhage while on blood thinners, so I’m very nervous about over-correcting this problem.

I’m being referred to an maternal fetal medicine specialist. I’m hoping that she’ll be willing to let me try low-dose aspirin and dietary changes to sustain the next pregnancy. It’s really frustrating that there are virtually no studies on the effectiveness of standard treatments. Especially since the treatments carry such significant risks.