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What is Thrombophilia?

  • Thrombophilia is a condition that is either genetic or acquired.
  • People with thrombophilia are at a higher risk of developing blood clots including DVT (deep vein thrombosis) and PE (pulmonary emboli)
  • Pregnant women with genetic or acquired thrombophilia are at greater risk of experiencing complications including pre-term birth.
  • Rare blood clots have been associated with the Oxford Astrazeneca Covid vaccine, however professionals recommend the benefits of the vaccine outweigh the risks of thrombosis.

What is thrombophiila

Thrombophilia is a medical condition where a person has an increased risk of developing dangerous blood clots in the veins or arteries. 

When haemostasis, the normal clotting process in the blood, is altered it results in a person’s blood clotting more readily. This can lead to a thrombus (blood clot) forming in the blood vessels. A thrombus is a clump of blood cells (platelets, fibrin and other blood components) that attaches to the wall of a blood vessel. Sometimes part of the blood clot breaks off and travels towards the lungs with potentially serious consequences. 

Deep vein thrombosis (DVT) is when a blood clot forms in a deep vein, and pulmonary embolism (PE) is when a blood clot travels through the body and gets caught in one of the pulmonary arteries in the lungs, blocking blood flow to the lungs

When DVT and pulmonary embolism occur together it’s called venous thromboembolism (VTE).  

Common causes of thrombophilia

Thrombophilia is either genetic or acquired (has no link with genes). 

Genetic types of thrombophilia are “abnormalities of the genes that are responsible for making coagulation proteins” and include:  

  • Factor V Leiden, a mutation of the F5 gene
  • Prothrombin thrombophilia, a mutation of the F2 gene
  • Congenital dysfibrinogenemia, a bleeding disorder  
  • Hereditary antithrombin deficiency
  • Heterozygous protein C deficiency
  • Heterozygous protein S deficiency

Acquired thrombophilia is when non-hereditary conditions increase the risk of blood clots, such situations include:

  • Antiphospholipid syndrome (APS)
  • Cancer and some medications that treat cancer
  • Human immunodeficiency virus (HIV)
  • Prolonged bed rest following an operation, during an illness or hospital stay
  • Prolonged periods of immobility during a long journey
  • Obesity
  • Pregnancy
  • Hormone replacement therapy (HRT) and the contraceptive pill

Symptoms of thrombophilia. How do I know if I have a blood clot?

Typically, you won’t realise you have thrombophilia until you have symptoms of a blood clot. If you do experience any DVT or PE symptoms, it’s important to act quickly. The UK’s National Health Service (NHS) lists the signs to look for under urgent and emergency attention. 

Signs of a DVT in your leg or other part of your body, urgent attention is needed:

  • Throbbing or cramping pain in the calf or thigh of one leg
  • Swelling in one leg
  • Skin warm to touch or red and darkened on one leg
  • Swollen, hard or sore veins

Signs of a pulmonary embolism or other serious condition, immediate emergency attention is required:

  • Severe difficulty breathing 
  • Heart beating very fast
  • Chest pain or discomfort and coughing 
  • A person has passed out

Will thrombophilia affect my pregnancy?

The risk of thrombophilia affecting a pregnancy is higher for women with certain types of acquired and genetic thrombophilia, with increased chance of pre-eclampsia, placental abruption, miscarriage and preterm birth.  

Most women will have healthy pregnancies. However, if you are pregnant or trying to become pregnant and have genetic or acquired thrombophilia speak to your healthcare team about an appropriate plan for managing your pregnancy. 

Is it safe to take HRT for menopause if I carry a risk of blood clots?

Much of what we have been told about the link between HRT and blood clots comes from dated research when the older forms of oestrogen and synthetic progesterone were widely used in HRT. 

In fact, for menopausal women with an acquired or inherited clotting disorder Thrombosis UK tells us that transdermal oestrogen, absorbed through the skin, is safer for menopausal women to take than the oral oestrogen pill, as it does not cause blood changes that could increase the risk of a blood clot. 

“For most women, the benefits of HRT outweigh the risks. For those at risk of a blood clot, HRT is safest when oestrogen is absorbed through the skin and micronised progesterone is used.”

Can I take the oral contraceptive pill if I have a blood clotting disorder?

Oestrogen in the combined contraceptive pill can increase the risk of a blood clot. The NHS describes this risk as “very small, but your doctor will check if you have certain risk factors before prescribing the pill.” 

Is it safe to have any of the Covid vaccines if I have thrombophilia?

Jo Jerrome, chief executive of Thrombosis UK was quoted as saying: “Having a previous thrombosis or thrombophilia (sticky blood) is not a risk factor for developing the rare post-Covid-19 vaccine thrombosis and thrombocytopenia.” 

Although there have been some rare blood clots associated with the Oxford AstraZeneca vaccine, the scientific advice puts the risk-benefit strongly in favour of the vaccine. Seek medical advice if you are unsure.

How is thrombophilia diagnosed?  

Thrombophilia is usually diagnosed only after a blood clotting event. Blood tests will determine whether you have acquired or inherited hypercoagulable states and whether you are at risk of further clotting. You will need to wait around 6-8 weeks after a significant blood clotting event, and after you have stopped taking anticoagulant medication, before the tests can be carried out.

Can thrombophilia be treated?

The following recommendations should be provided by your healthcare team to treat blood clots resulting from thrombophilia:

  • Anticoagulant medication
  • Compression socks
  • Regular physical activity
  • Drinking lots of water
  • Lifestyle changes

Depending on the severity of the clot, your healthcare team may also recommend continued anticoagulant medication and regular health check-ups.

Nabta is reshaping women’s healthcare. We support women with their personal health journeys, from everyday wellbeing to the uniquely female experiences of fertility, pregnancy, and menopause. You can track your symptoms and get personalised support by using the Nabta app.

Get in touch if you have any questions about this article or any aspect of women’s health. We’re here for you. 


“Practical guidance for the prevention of thrombosis and management of coagulopathy and disseminated intravascular coagulation of patients infected with COVID-19” Thombosis UK, https://thrombosisuk.org/covid-19-thrombosis.php

“Thrombophilia” Patient, https://patient.info/allergies-blood-immune/blood-clotting-tests/thrombophilia

“Pulmonary Embolism”, Mayo Clinic https://www.mayoclinic.org/diseases-conditions/pulmonary-embolism/symptoms-causes/syc-20354647

What is Thrombophilia? Vascular Cures https://vascularcures.org/thrombophilia/

“Thrombophilia”, NHS https://www.nhs.uk/conditions/thrombophilia/

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