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F5 (Factor V) and Fertility: What Your Genotype Means for Reproductive Health

Infertility can have many causes. One contributor is how the body controls blood clotting. The F5 gene helps regulate clotting through the protein Factor V. A common change in F5, known as Factor V Leiden (rs6025), can increase the tendency to form abnormal blood clots. In pregnancy, clotting problems can affect blood flow in the placenta and raise the risk of pregnancy complications, including recurrent miscarriage.

This article explains what each rs6025 genotype can mean for fertility and pregnancy, and provides practical, user friendly recommendations for diet, supplements, lifestyle, monitoring, and planning. PlexusDx does not provide medical advice. Always discuss your results with your healthcare provider before making health or treatment decisions.

How clotting changes fertility

Clotting is essential to stop bleeding, but too much clotting can block small placental blood vessels. When placental perfusion is impaired, the developing embryo or fetus may receive less oxygen and nutrients, which can contribute to miscarriage or other pregnancy problems. Factor V Leiden changes how Factor V is broken down in the clotting cascade, increasing clot stability and the risk of thrombosis in some people.

2 effect alleles (TT) — Factor V Leiden homozygous

If your genotype is TT at rs6025, you have two copies of the effect allele and are considered homozygous for Factor V Leiden. This genotype is associated with a substantially increased risk of abnormal blood clot formation compared to people without the variant. During pregnancy this can raise the risk of recurrent miscarriage and other placental complications.

Recommendations

  • Consult a specialist in thrombophilia or maternal fetal medicine before conceiving or as soon as possible in pregnancy.
  • Discuss prophylactic anticoagulation options. Low molecular weight heparin or other blood thinning strategies are sometimes recommended under medical supervision to lower clot risk during pregnancy and the postpartum period.
  • Plan enhanced monitoring in pregnancy. This may include more frequent visits, fetal growth checks, and targeted ultrasound assessments of placental and fetal well being.
  • Avoid smoking and unnecessary estrogen containing medications. Smoking and exogenous estrogens both increase clot risk.
  • Stay active and avoid prolonged immobility. Break up long periods of sitting or travel with movement and calf muscle exercises.
  • Hydration: maintain good fluid intake to reduce blood viscosity.
  • Consider dietary focus on anti inflammatory foods and omega 3 fatty acids. Discuss supplements with your provider.
  • Inform your care team of your genotype for delivery planning and postpartum thrombosis prevention.
1 effect allele (CT) — Factor V Leiden heterozygous

If your genotype is CT, you carry one copy of the effect allele. This heterozygous state increases your risk of clot formation relative to the common genotype, but the risk is typically lower than with two copies. Even so, this variation can still affect pregnancy through placental clotting and may be associated with recurrent miscarriage in some people.

Recommendations

  • Talk with your primary care provider or an obstetrician knowledgeable about thrombophilia when planning pregnancy or if you have a history of miscarriage or clotting events.
  • Individualized risk assessment may lead to watchful waiting, increased prenatal monitoring, or short term anticoagulation in pregnancy depending on personal and family history.
  • Follow lifestyle measures to lower clot risk: avoid tobacco, limit exposure to unnecessary estrogens, stay mobile during travel, and maintain healthy weight.
  • Keep well hydrated and include foods rich in omega 3 fatty acids like fatty fish, walnuts, and flaxseed.
  • Discuss the use of supplements such as prenatal vitamin with folic acid and any additional interventions with your provider.
  • If you have other risk factors for thrombosis such as obesity, recent surgery, a personal or family history of clotting, or prolonged immobility, these should be managed proactively.
0 effect alleles (CC) — No Factor V Leiden variant

If your genotype is CC, you do not carry the Factor V Leiden variant. Your clotting function is typical for this genetic site and you are not at elevated genetic risk for thrombophilia from this F5 change. This does not guarantee no risk of clotting, since non genetic factors also contribute.

Recommendations

  • Maintain general reproductive and cardiovascular health: avoid smoking, stay active, manage weight, and follow routine prenatal care.
  • Follow a balanced diet rich in leafy greens, lean proteins, whole grains, and sources of omega 3 fats.
  • Practice good hydration and avoid long periods of immobility when traveling or recovering from illness.
  • If you have personal or family history of clotting events or recurrent miscarriage, discuss further evaluation with your healthcare provider as other genetic or acquired causes may exist.

Diet, supplements, and lifestyle to support healthy pregnancies

For people with or without the Factor V Leiden variant, the following steps support overall reproductive health and reduce additional clotting risk factors.

  • Balanced diet: emphasize whole foods, vegetables, fruits, lean proteins, and whole grains. Leafy greens provide folate and other nutrients important for early pregnancy.
  • Omega 3 fatty acids: include fatty fish like salmon two times per week or discuss a fish oil supplement with your provider if intake is low. Omega 3s support healthy blood flow and reduce inflammation.
  • Maintain healthy weight: excess weight increases clotting risk and pregnancy complications.
  • Avoid tobacco: smoking increases both clotting risk and obstetric complications.
  • Limit or avoid unnecessary estrogen containing medications: combined hormonal contraceptives and some hormone therapies can raise clot risk. Discuss alternatives with your clinician.
  • Exercise: aim for regular moderate exercise such as brisk walking, swimming, or prenatal exercise classes once pregnant and cleared by your provider.
  • Hydration and mobility: drink adequate fluids and move regularly during long travel or bed rest periods.
  • Stress management and sleep: reduce chronic stress and prioritize restorative sleep, both important for fertility and overall health.

Monitoring and testing to consider

  • Preconception consultation: review family and personal clotting history. A hematology or maternal fetal medicine consult may be appropriate if you carry the variant or have recurrent pregnancy loss.
  • Pregnancy monitoring: enhanced fetal growth surveillance and placental assessment may be recommended when clotting risk is elevated.
  • Anticoagulation planning: if anticoagulation is recommended, have a clear plan for dosing, monitoring, and postpartum management.
  • Additional testing: your clinician may check other inherited or acquired thrombophilias, hormone levels, or autoimmune markers depending on your history.

Important note from PlexusDx

PlexusDx provides educational information about genetic predispositions. This content is not medical advice. Genetic results are one piece of health information and must be interpreted together with personal medical and family history. Always consult your healthcare provider, a genetic counselor, or a specialist before starting or stopping any medication, supplement, or treatment.