The Link Between Factor V Leiden and Recurrent Miscarriages

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When your blood clots, many of the proteins in your body, among them Factor V, work together to make that happen; Factor V Leiden is a genetic variation of Factor V that affects the blood-clotting process and makes a person more likely to form blood clots.

Learn more about this genetic variation and what effect it may have on your pregnancy with this review.

Copies of the Factor V Leiden Gene

A person can have one copy of the Factor V Leiden gene and one normal copy (meaning the person is heterozygous), or a person can have two copies of the Factor V Leiden gene (the person is homozygous).

Some doctors recommend heparin for women with recurrent miscarriages who test positive for Factor V Leiden. Ask your doctor if she recommends heparin, another medication or no medication at all for you.

Protein C Resistance

The Factor V Leiden gene is also associated with a condition called activated protein C resistance. Protein C is another protein involved in the clotting process. The majority of people with activated protein C resistance also have the Factor V Leiden genetic variation.

So, many women who haven't been specifically tested for the Factor V Leiden gene may discover that they're carriers after testing positive for protein C.


About 4 percent to 7 percent of the population is heterozygous for Factor V Leiden. Around 0.06 percent to 0.25 percent of the population is homozygous for Factor V Leiden. Different ethnic groups have different rates of the Factor V Leiden mutation; it is most common in people from northern Europe.

Talk to your doctor about whether or not you're at risk.


Factor V Leiden means an increased risk of deep vein thrombosis and medically important blood clots.

Some studies have found that having the Factor V Leiden mutation means an increased risk of recurrent miscarriages, possibly because of tiny blood clots blocking the flow of nutrients to the placenta.


In pregnancy, some doctors believe in using heparin and/or low-dose aspirin to treat women who have the Factor V Leiden gene and a history of miscarriages. Currently, researchers are still studying this treatment to verify that it actually helps. Many fertility clinics recommend that patients take baby aspirin during treatment just in case they have clotting problems.

Relationship to Miscarriages

Researchers are still studying the exact nature of the relationship between Factor V Leiden (and other hereditary thrombophilias) and recurrent miscarriages.

Different genetic blood clotting disorders have different levels of relationship to miscarriage, but Factor V Leiden is one of the hereditary thrombophilias that does appear to have a role in causing miscarriages (or at least increasing risk) because women with the mutation have a higher rate of miscarriages than women without it.

Available research suggests that Factor V Leiden can play a role in miscarriages that happen after 10 weeks but it is less likely to be a factor in early miscarriages.

Many doctors do test for Factor V Leiden as a part of the recurrent miscarriage workup of tests and recommend treatment for those who test positive.

7 Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Kumar A, Misra S, Sagar R, et al. Relationship between Factor V Leiden Gene Variant and Risk of Ischemic Stroke: A Case-Control Study. Ann Indian Acad Neurol. 2017;20(3):284-288. doi:10.4103/aian.AIAN_31_17

  2. Yuksel H, Kayatas S, Boza AT, Api M, Ertekin AA, Cam C. Low molecular weight heparin use in unexplained recurrent miscarriage. Pak J Med Sci. 2014;30(6):1232-7. doi:10.12669/pjms.306.5477

  3. Jadaon MM. Epidemiology of activated protein C resistance and factor v leiden mutation in the mediterranean region. Mediterr J Hematol Infect Dis. 2011;3:e2011037. doi:10.4084/MJHID.2011.037

  4. Favaloro EJ, Mcdonald D. Futility of testing for factor V Leiden. Blood Transfus. 2012;10(3):260-3. doi:10.2450/2012.0097-12

  5. Rodger MA, Betancourt MT, Clark P, et al. The association of factor V leiden and prothrombin gene mutation and placenta-mediated pregnancy complications: a systematic review and meta-analysis of prospective cohort studies. PLoS Med. 2010;7(6):e1000292. doi:10.1371/journal.pmed.1000292

  6. Karadağ C, Akar B, Gönenç G, Aslancan R, Yılmaz N, Çalışkan E. Aspirin, low molecular weight heparin, or both in preventing pregnancy complications in women with recurrent pregnancy loss and factor V Leiden mutation. J Matern Fetal Neonatal Med. 2020;33(11):1934-1939. doi:10.1080/14767058.2019.1671348

  7. Battinelli EM, Marshall A, Connors JM. The role of thrombophilia in pregnancy. Thrombosis. 2013;2013:516420. doi:10.1155/2013/516420

Additional Reading
  • Coulam, C.B., R.S. Jeyendran, L.A. Fishel, and R. Roussev, "Multiple Thrombophilic Gene Mutations Rather Than Specific Gene Mutations Are Risk Factors for Recurrent Miscarriage." American Journal of Reproductive Immunology May 2006. 

  • Foka, Z.J., A.F. Lambropoulos, H. Saravelos, G.B. Karas, A. Karavida, T. Agorastos, V. Zournatzi, P.E. Makris, J. Bontis, and A. Kotsis, "Factor V Leiden and Prothrombin G20210A Mutations, But Not Methylenetetrahydrofolate Reductase C677T, Are Associated With Recurrent Miscarriages." Feb 2000. 

  • Jivraj, S., R. Rai, J. Underwood, and L. Regan, "Genetic Thrombophilic Mutations Among Couples With Recurrent Miscarriage." Human Reproduction May 2006. 

  • Reznikoff-Etievan, M.F., V. Cayol, B. Carbonne, A. Robert, F. Coulet, and J. Milliez, "Factor V Leiden and G20210A Prothrombin Mutations Are Risk Factors for Very Early Recurrent Miscarriage.' BJOG Dec 2001. 

  • Walker, M.C., S.E. Ferguson, and V.M. Allen, "Heparin for Pregnant Women With Acquired or Inherited Thrombophilias." The Cochrane Library 21 Jan 2003. 

  • University of Illinois - Urbana/Champaign, "Patient Resources: Factor V Leiden." Hematology Resource Page

By Krissi Danielsson
Krissi Danielsson, MD is a doctor of family medicine and an advocate for those who have experienced miscarriage.