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Your pregnancy and baby guide

Deep vein thrombosis (DVT) in pregnancy

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Deep vein thrombosis (DVT) is a serious condition where a blood clot forms in a deep vein in the body, usually in the leg.

Urgent advice: Call your midwife, GP or maternity unit immediately if you have:

  • pain, swelling and tenderness in one leg, usually at the back of your lower leg (calf) – the pain may be worse when you bend your foot up towards your knee
  • a heavy ache or warm skin in the affected area
  • red skin, particularly at the back of your leg below the knee

These can be signs of deep vein thrombosis. It usually happens in only one leg, but not always.

If the clot breaks off into the bloodstream, it can block one of the blood vessels in the lungs. This is called a pulmonary embolism (PE) and needs emergency treatment.

Immediate action required: Call 999 immediately if you:

  • have sudden difficulty breathing
  • have pain or tightness in your chest or upper back
  • are coughing blood

These can be signs of a blood clot in the lungs (pulmonary embolism).

PE can be fatal, but the risk of developing a PE is very small if DVT is diagnosed and treated. Read more about DVT.

DVT isn't common in pregnancy. But pregnant women at any stage of pregnancy, and up to 6 weeks after the birth, are more likely to develop DVT than non-pregnant women of the same age.

DVT doesn't always have symptoms.

During pregnancy it's common to experience swelling or discomfort in your legs, so this on its own doesn't always mean there's a serious problem.

Are you at risk?

Your risk of developing DVT during pregnancy is even greater if you:

  • or a close family member have had a blood clot before
  • are over 35
  • are obese (have a BMI of 30 or more)
  • have had a severe infection or recent serious injury, such as a broken leg
  • have a condition that makes clots more likely (thrombophilia)
  • are carrying twins or multiple babies
  • have had fertility treatment
  • are having a caesarean section
  • smoke – get support to stop smoking
  • have severe varicose veins (ones that are painful or above the knee with redness or swelling)
  • are dehydrated

Managing DVT in pregnancy

If you develop a DVT while pregnant, you'll probably need injections of a drug to stop the blood clot getting bigger so your body can dissolve it.

The drug, called heparin, doesn't affect your developing baby.

Read more about treating DVT.

The injections also reduce your risk of getting a PE and developing another clot.

You'll usually need to have the injections for the rest of your pregnancy and until at least 6 weeks after the birth of your baby. You may need to have the injections for up to 3 months in total.

Although medical treatment for DVT is essential, there are also things you can do to help yourself.

These include:

  • staying as active as you can – your midwife or doctor can advise you on this
  • wearing prescribed compression stockings to help the circulation in your legs

Travel and DVT

Travelling for longer than 4 hours (long-haul travel) increases your risk of developing DVT.

It's not known if this risk is greater during pregnancy, but to reduce the risk of DVT while you're travelling:

  • drink plenty of water
  • avoid drinking alcohol in pregnancy
  • perform simple leg exercises, such as regularly flexing your ankles – if you're on a flight, most airlines provide information on suitable exercises to do during your flight
  • if possible, walk about during refuelling stops or walk up and down the bus, train or plane (when it's safe to do so) has videos and written interviews of women talking about their experiences of having a blood clot in pregnancy.

Page last reviewed: 04/10/2019
Next review due: 04/10/2022