Reducing your risk of bloods clots
There is a lot to learn during pregnancy — how your baby develops, how your body changes, and what signs to look out for.
One possible risk during pregnancy, and for up to six weeks after birth, is developing a blood clot (also known as a venous thromboembolism or VTE).
Most women will not experience a blood clot during pregnancy – around 1-2 in every 1000 pregnant women are affected.
However, understanding your personal risk, recognising symptoms early and taking any recommended preventative treatment can significantly reduce the chance of complications.
Why is pregnancy a risk for blood clots?
During pregnancy, your blood naturally becomes “stickier” to help reduce bleeding during birth. This helpful change can also slightly increase the chance of blood forming a clot.
A blood clot that forms in a deep vein — usually in the leg — is called a deep vein thrombosis (DVT).
A blot clot or part of a clot that has broken off and travelled to the lungs – is called a Pulmonary Embolism (PE).
Some people have medical conditions or personal histories that increase the risk further. In those cases, we may recommend a once‑daily blood‑thinning medication called low molecular weight heparin (LMWH). This medicine is safe for you and your baby.
You will have a personalised blood‑clot (VTE) risk assessment at every maternity appointment and during any hospital admission.
What factors may increase my risk?
You may have a higher chance of developing a blood clot if one or more of the following apply to you:
- Age over 35
- Being overweight
- Having an emergency caesarean birth
- Reduced mobility (e.g., being unable to move around as normal)
- Severe nausea or vomiting leading to dehydration
- Certain medical or autoimmune conditions
- Known clotting disorders (that increase your clotting)
- A previous DVT or pulmonary embolism
- Smoking
Having more than one factor can increase your risk further.
How can I reduce my risk?
There are simple steps you can take to help lower your risk, including:
- Stopping smoking
- Staying active and mobile
- Maintaining a healthy weight
- Keeping well hydrated
However, some women may need medication during pregnancy and/or after birth to help prevent clots. Early risk assessment is important because starting treatment early when it is required can reduce the chance of a blood clot developing.
Early assessment of VTE risk
If you have had a previous blood clot in your leg (DVT) or lung (pulmonary embolism), or if you have a condition that increases your risk, it is important to be assessed early in pregnancy.
If you have just found out you are pregnant, a national self‑assessment tool is available to help you check if you have any risk factors that mean you may need early treatment.
If you answer “yes” to one or more of the questions, you may require LMWH treatment. You should contact your GP or your maternity service through the self‑referral booking pathway as soon as possible.
Access your Self-assessment tool
If you are reading this site through an accessibility tool and you cannot open and translate the attached risk assessment forms, you can access them and translate them through Just One Norfolk. Or alternatively please get in touch with us via email to contact.midwiferyteam@nnuh.nhs.uk or telephone via 01603 287239.
What are the signs of a venous thromboembolism?
Signs of a DVT (leg blood clot):
- Pain or tenderness in your leg
- Swelling in one leg
- Discolouration (pale, blue, or reddish‑purple skin)
- Swelling of the whole leg (if the clot is higher in the thigh veins)
If you notice these symptoms, contact your GP, midwife or maternity team immediately.
Signs of a pulmonary embolism (PE) – a medical emergency:
A PE happens when a clot moves to the lungs and can be life threatening. Symptoms include:
- Sudden shortness of breath
- Unexplained breathlessness
- Chest pain
- Fast heartbeat
- Coughing up blood‑streaked mucus
If you have symptoms of a PE, go to the Emergency Department immediately.
Learn more about the signs and symptoms of blood clots in pregnancy.
Importantly, if something doesn’t feel right, or if you have concerns about your risk factors, prescribed medication or symptoms, please contact your midwife, GP, or maternity team straight away.
We are here to support you throughout your pregnancy and after birth, and early advice or treatment can make a real difference to your wellbeing and your baby’s safety.
How is a DVT diagnosed?
The diagnosis of a DVT in pregnancy is usually confirmed by an ultrasound of the leg. This will usually show up with a blood clot in the large vein at the top of the leg. The ultrasound is the same type of scan used to check your baby’s progress and growth during pregnancy, so it is completely safe.
How is a blood clot treated?
Treatment for DVT or PE during pregnancy is similar to treatment outside pregnancy.
You will usually be given low molecular weight heparin (LMWH).
This medicine “thins” the blood to stop the clot getting bigger and allows your body to break it down naturally. It is given as a small injection under the skin.
External links
Thrombosis and pregnancy leaflet from Thrombosis UK
Treating blood clots during pregnancy leaflet from Thrombosis UK