Low-dose aspirin in pregnancy to prevent pre-eclampsia

Pre-eclampsia is a high-blood pressure condition that usually happens towards the end of pregnancy. You might not notice the symptoms of pre-eclampsia but we will pick these up during your routine antenatal visits.

If you are at greater risk of pre-eclampsia, we recommend that you take a low dose of aspirin every day. There is evidence that taking aspirin during pregnancy reduces the risk of pre-eclampsia.

If you have previously had stomach ulcers, bleeding disorders or asthma, please ask your doctor before taking aspirin.

How we assess your risk of pre-eclampsia

Pre-eclampsia happens in around 2 to 5 in every 100 pregnancies. Some people are more at risk than others.

At your first midwife appointment, we will ask you some questions. These questions tell us if you are at high or moderate risk of getting pre-eclampsia.

We ask you to take low-dose aspirin for the rest of your pregnancy if you have 1 high risk factor or 2 moderate risk factors.

High risk factors

You'll have low-dose aspirin if you have 1 or more high risk factors, which include:

  • high blood pressure, before or during pregnancy
  • problems in previous pregnancies
  • chronic kidney disease
  • any auto-immune disease, such as antiphospholipid syndrome (APS)
  • diabetes

Moderate risk factors

You'll have low-dose aspirin if you have 2 or more moderate risk factors, which include:

  • this being your first pregnancy
  • 40 years of age and over
  • obesity with a body mass index (BMI) of more than 35
  • expecting twins (or multiple births)
  • having a family history of pre-eclampsia

How to take low-dose aspirin

You should start taking low-dose aspirin between 12 to 16 weeks pregnant, ideally at 12 weeks. Low-dose aspirin started earlier than this is safe and may bring increased benefits but this has not been proven.

You should take 75 to 150mg of aspirin with food, every evening.

It does not matter if you occasionally miss a dose.

You can get a prescription for aspirin from your GP or buy it from any chemist.

We recommend you continue taking low-dose aspirin until 36 weeks of pregnancy. You should continue to take the aspirin through the whole of your pregnancy.

We continue to monitor you throughout your pregnancy. We test your blood pressure and urine at your antenatal visits to check for signs of pre-eclampsia. How frequently we monitor you at appointments will depend on your individual health.

Please note, we do not recommend taking high-dose aspirin (more than 150mg) during pregnancy.

Taking aspirin for other reasons

Sometimes, your doctor will advise you to take aspirin for other reasons. For example, if your blood test as part of the early pregnancy screening at 11 to 14 weeks shows low levels of a placental protein called PAPP-A, or if you have sickle cell disease.

Unlicensed medicine

Although we recommend that you take aspirin for this reason, it is an unlicensed use of the medicine. This means it is not officially approved as a treatment to reduce the risk of pre-eclampsia.

Many medicines recommended in pregnancy may not be licensed but are safe to use for most people.

Read our information about unlicensed medicines.

Symptoms of pre-eclampsia

The common signs of pre-eclampsia are raised blood pressure and protein in your urine.

Further symptoms can include:

  • headaches
  • visual disturbance (blurred vision or flashing lights)
  • abdominal pain
  • reduced fetal movements
  • swelling in the hands, feet and face

If you have any of these symptoms, get advice immediately by calling NHS 111 or your GP.

If you are diagnosed with pre-eclampsia

When pre-eclampsia is diagnosed, we usually admit you to hospital until you deliver your baby.

We treat high blood pressure with medicine.

Pre-eclampsia begins to improve once the baby and placenta are delivered. Delivery is usually recommended around 37 weeks but may be offered earlier in some cases.

In rarer cases (around 5 in 1,000 pregnancies) pre-eclampsia leads to more severe complications. These may start earlier and affect your health, or the growth of the baby in the womb. In these cases the baby may need to be delivered earlier.

You can read more about treatment for pre-eclampsia on the NHS website.

Information and support

Action on pre-eclampsia has information and support.

Tommy's has information about pre-eclampsia.

Resource number: 4300/VER2
Last reviewed: April 2023
Next review: April 2026

Trusted Information Creator. Patient Information Forum

Contact us

If you have any questions about taking low-dose aspirin, please speak to the team caring for you.

You can also call our pharmacy medicines helpline on 020 7188 8748 Monday to Friday, 9am to 5pm.

If you have other concerns about your pregnancy, you can call the maternity helpline on 020 7188 1723 Monday to Friday, 10am to 6pm

Do you have any comments or concerns about your care?

Contact our Patient Advice and Liaison Service (PALS)

Is this health information page useful?