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Deep Vein Thrombosis

Deep Vein Thrombosis

A deep vein thrombosis or DVT occurs when blood forms into a clot (also known as a thrombus), whilst still in the veins. This happens most commonly in the veins of the legs. A DVT causes pain and swelling in the affected leg and sometimes parts of a large blood clot can also travel in the veins to other parts of the body, like the lungs, and cause very serious problems.

Blood in the circulatory system shouldn’t form large clots usually but some things can make your blood more likely to clot. You’ll have a higher chance of developing a DVT if you or a family member has had a blood clot before or has a condition that makes you blood more likely to clot, or if you’re immobile for a few days, for example when unwell. Other factors like being a smoker or having severe varicose veins can also increase the risk. Being pregnant does slightly increase the likelihood of blood clots forming, although DVTs are still quite uncommon in pregnancy.


The signs of a DVT include:

  • Swelling in the affected leg
  • Redness and warmth of the affected leg
  • Pain and tenderness of the leg


A blood clot that affects the lungs is known as a pulmonary embolism (PE) and can cause breathing difficulties and pain in the chest. It may also cause a collapse and can sometimes be fatal.

If you develop any of these symptoms then contact your health provider so they can assess you.  You may need to have a special ultrasound scan of your leg if a DVT is suspected.

A confirmed DVT requires treatment with blood thinning injections. These contain a drug called low molecular weight heparin, a medication that stops blood clotting. It prevents a DVT from growing and allows it to dissolve away again into the blood stream. It doesn’t affect your baby. The injections will usually continue up until your baby is born and for 6 weeks after that. In some cases, if you’ve had a blood clot in the past, you might need to stay on treatment for longer in order to prevent more clots in the future.

Article By

Dr Emma Scott (MBChB, MRCGP) is a qualified GP and mummy to two young children. She works in a GP practice in Edinburgh and in the out of hours GP service in Livingston and she has experience in both obstetrics & gynaecology and paediatrics.

to read more articles by Dr Emma

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