Thrombosis Australia

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Pregnancy increases your risk of thrombosis

Pregnancy can increase your risk of venous thromboembolism (VTE) which includes deep vein thrombosis (DVT) and pulmonary embolism (PE). However, it is important to remember that during pregnancy the risk of thrombosis only increases by 2 per 1000 pregnancies.

Pregnancy is thought to increase the risk of VTE due to:

  • The compression of blood vessels
  • Hypercoagulability or “Sticky blood” caused by increased hormones (such as oestrogen)
Pregnancy can increase your risk of VTE by 4- to 5-fold(1).

You are also at higher risk of thrombosis in the 6-week period following pregnancy.                                                                             

Who is more at risk of thrombosis while pregnant?

Below is a list of factors that increase your risk of VTE while pregnant:

  • Multiparity (having twins or more)
  • Age over 35 years
  • Preeclampsia/eclampsia (high blood pressure causing complications)
  • Gestational diabetes
  • Current infection
  • Obesity
  • Heart disease
  • Coronary artery disease
  • Hypertension
  • Recent major surgery, or surgery during pregnancy
  • Recent injury – especially in the legs
  • Cancer
  • Hormonal therapy
  • Certain medical conditions and deficiencies – see Inherited Thrombophilias
  • Family history of or previous thrombosis
  • Being unable to move for long periods of time
  • Smoking                                                                              

What are the risk factors after pregnancy?

You are also at higher risk of VTE in the period after pregnancy.

Below is a list of factors that increase your risk of VTE after birth:

  • Emergency or elective caesarean
  • Labour lasting longer than 24 hours
  • Stillbirth
  • Preterm birth
  • Large (1L) haemorrhage after birth
  • Long periods immobile (bed rest, long-distance travel)
  • Gestational diabetes
  • Infection
  • Preeclampsia/eclampsia (high blood pressure causing complications)                                                                                          

How can reduce the risk of thrombosis during pregnancy?

Most people, including those who are predisposed to increased blood clots, have successful pregnancies.

Below is a list of things that you can do to reduce your risk of thrombosis:

  1. Keep moving:
    • It is important to remain mobile during your pregnancy, move around and stretch often.
  2. Stay hydrated:
    • Hydration helps to prevent your blood from clotting.
  3. Wear graduated compression stockings:
    • Evidence suggests wearing compression stockings can help prevent VTE in non-pregnant hospitalised patients. Ask your doctor about compression stockings to find out whether this is a good option for you.
  4. Blood-thinning medication:
    • If you are at high risk of developing VTE during your pregnancy, it may be necessary for you to take medication that prevents thrombosis. There are medications that do not cross the placenta and are suitable for breastfeeding - talk to your doctor about medication suitable for you. 

Talk to your doctor to learn the risk factors and options most suited to preventing VTE during pregnancy. 

Pregnancy and thrombosis FAQs:

Why does pregnancy increase your risk of developing thrombosis?

While you are pregnant your oestrogen levels are higher than normal – which is thought to be the cause of the increased risk of thrombosis during pregnancy. Oestrogen increases the levels of clotting factors in the blood which makes your blood more likely to clot.

How can I reduce my risk while I’m pregnant or in hospital?

See here for a list of things you can do to prevent thrombosis during pregnancy.

Am I still at risk of developing thrombosis after giving birth?

Yes. Your risk of thrombosis is increased for the 6-week period after you give birth. Other factors that may increase your risk after giving birth are listed here.                   

Learn more about thrombosis.

Download a leaflet version of this page.

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  1. Department for Health and Ageing, Government of South Australia. Thromboprophylaxis and Thromboembolic Disease in Pregnancy. South Australian Perinatal Practice Guideline 2004; Reviewed May 2018.
  2. North Metropolitan Health Service, Government of Western Australia. VTE occurring in the present pregnancy and puerperium. Clinical Practice Guideline 2004; Reviewed Feb 2019. 
  3. Department of Health, Government of Queensland. Venous Thromboembolism (VTE) prophylaxis in pregnancy and the puerperium. Maternity and Neonatal Clinical Guideline 2014; Reviewed Feb 2019.