Articles

Key takeaways

• Pregnancy increases the risk of blood clots, although they remain uncommon.
• Seek urgent medical help if you have symptoms of DVT or pulmonary embolism (PE).
• Staying active, keeping hydrated, and stopping smoking can help reduce your risk.
• Some pregnant people may need daily low-molecular-weight heparin (LMWH) injections during pregnancy and after birth.

Understanding blood clots and their symptoms

A blood clot in a deep vein is called a deep vein thrombosis (DVT). It often forms in the leg, calf, or pelvis.

Symptoms of a DVT usually appear in one leg and may include:

• Swelling
• Pain
• Tenderness
• Warmth
• Redness

While DVT is uncommon, your risk is increased throughout pregnancy and after birth. A DVT can occur at any time, including the first three months of pregnancy. The risk of blood clots is highest in the first few weeks after birth and remains increased until six weeks after birth.

Why it's important to treat DVT

It's important to treat a DVT because part of the blood clot can sometimes break off and travel in your bloodstream. If it travels to the lungs, it can cause a blockage called a pulmonary embolism (PE).

A PE is a serious condition that needs urgent medical attention and treatment. Thankfully, this is very rare during pregnancy, and getting treatment quickly makes it less likely to become life-threatening.

Symptoms of a pulmonary embolism

Symptoms of a PE can include:

• Sudden unexplained shortness of breath
• Tightness in the chest or chest pain
• Coughing up blood
• Feeling very unwell
• Collapse or loss of consciousness

A PE is a medical emergency that requires urgent assessment and treatment. Although it is uncommon in pregnancy, getting treatment quickly can be lifesaving.

You should call 999 or attend hospital immediately if you experience any of these symptoms.

General prevention strategies for everyone

There are several things you can do to help reduce your risk of getting a DVT or PE. Staying active is important.

Your midwife or doctor can advise you on safe exercise during pregnancy. Keeping hydrated by drinking normal amounts of fluids also helps. If you smoke, stopping can reduce your risk.

Compression stockings

Wearing special stockings (graduated elastic compression stockings) can help prevent blood clots. They help improve blood flow in your legs. Your healthcare team can advise whether compression stockings are recommended and ensure you have the correct size and type.

Travel and DVT risk

Long-distance travel, meaning journeys longer than four hours, carries a small risk of DVT. You can take steps to reduce your risk while travelling, including:

• Drinking plenty of water and avoiding alcohol.
• Doing simple leg exercises, such as regularly flexing your ankles.
• Walking around when it is safe to do so.
• Wearing loose clothing and comfortable shoes.
• Consider graduated elastic compression stockings if advised by your healthcare professional.

Medical treatment for those at higher risk

If you are at a higher risk of blood clots, you may be advised to start treatment. This treatment involves injections of a blood-thinning medicine called heparin. The most commonly used type in pregnancy is low-molecular-weight heparin (LMWH). This medication is safe to take during pregnancy.

Who may be offered LMWH?

You may be offered LMWH if you have one or more risk factors for developing blood clots. In many cases, LMWH is only recommended when several risk factors occur together. The number and importance of the risk factors determine whether injections are recommended from early in pregnancy, the third trimester onwards, or after birth.

• A previous DVT or PE
• Certain blood clotting disorders
• Certain medical conditions, such as heart or lung disease
• Obesity
• Prolonged immobility
• Varicose veins
• Being over 35 years of age
• Already having 3 or more children
• Multiple pregnancy
• Hyperemesis gravidarum (severe sickness during pregnancy)
• Major surgery, including some caesarean births

Your healthcare team will assess your individual risk and discuss whether treatment is recommended.

How LMWH works

This medicine is a blood thinner (also known as an anticoagulant). The dose used to prevent a blood clot is usually less than the dose used to treat one.

For most pregnant people, the benefits of LMWH are that it:

• Reduces the risk of developing a DVT or a PE.
• Reduces the risk of blood clots returning if you have had one before.

A practical guide to LMWH injections

Heparin is given as an injection under the skin (a subcutaneous injection). You will usually take it at the same time every day. You will be given pre-filled needles and syringes.

Here’s a practical guide to administering your LMWH injection:

1. Prepare – Wash your hands thoroughly. Gather your pre-filled syringe and an alcohol wipe.
2. Choose an injection site – Select an area on your abdomen or outer thigh, at least two inches from your belly button if using the abdomen. Rotate sites daily to prevent bruising and irritation.
3. Clean – Clean the chosen skin area with the alcohol wipe and let it air dry completely.
4. Inject – Pinch a fold of skin, then insert the needle straight into it. Push the plunger slowly and steadily until all the medicine is injected.
5. Withdraw – Release the pinched skin and withdraw the needle straight out. Do not rub the injection site.
6. Dispose – Immediately place the used syringe into a sharps disposal container. You will be shown how to store and get rid of them safely.

Do not stop taking LMWH without speaking to your healthcare team. They will advise you when to stop treatment, including when labour starts or before a planned birth.

Possible side effects

You may get some bruising where you inject. This bruising will usually fade within a few days.

Around 1–2 in 100 people may develop an allergic reaction. If you notice a rash after injecting, you should let your doctor know. They can change the type of heparin you are using.