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Deep vein thrombosis in pregnancy

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 GP, midwife or 111 immediately if you have:

  • pain, swelling and tenderness in 1 leg, usually at the back of your lower leg (calf) – the pain may be worse when you walk
  • 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 1 leg, but not always.

If the clot breaks off into the bloodstream, it can block 1 blood vessel 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 is not common in pregnancy. But you're more likely to develop DVT at any stage of your pregnancy and up to 6 weeks after the birth than people of the same age who are not pregnant.

DVT does not always have symptoms.

During pregnancy it's common to have swelling or discomfort in your legs, so this on its own does not 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 body mass index 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 medicine to stop the blood clot getting bigger so your body can dissolve it.

The medicine, called heparin, does not 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.

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 about exercises you can do to during the 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 people talking about their experiences of having a blood clot in pregnancy

Page last reviewed: 23 April 2021
Next review due: 23 April 2024