Low dose aspirin (150mg) in pregnancy

You have been given this information leaflet as you have been advised to take low dose aspirin. Take 150mg once a day from 12 weeks until the birth of your baby.

What is aspirin?

Aspirin is known as an NSAID (a non-steroidal anti-inflammatory drug). Aspirin is often used to treat pain, fever, inflammation, or prevent clot formation.

There is evidence that taking low dose aspirin once a day can help increase the function and blood flow of your placenta (afterbirth). The placenta provides your baby with oxygen and nutrients to help them grow.

Why have I been advised to take aspirin?

Not everyone is recommended to take aspirin in pregnancy. You have been advised to take a low dose of aspirin during your pregnancy to reduce the risk of:

• developing hypertension (high blood pressure); and

• pre-eclampsia (high blood pressure and protein in your urine)

• giving birth to your baby prematurely (before 37 weeks)

• your baby being smaller than expected.

If any of the following apply, you will have been advised to take low dose aspirin. This is to reduce your risk of hypertension (high blood pressure) in pregnancy.

• You had hypertension (high blood pressure) during a previous pregnancy.

• You have chronic kidney disease.

• You have an auto-immune disease (for example lupus or antiphospholipid syndrome).

• You have Type 1 or 2 diabetes.

• You have chronic hypertension (high blood pressure before pregnancy).

• You have previously given birth to a baby who was smaller than expected.

• You have low Pregnancy Associated Plasma Protein (PAPP-A) screening blood test.

• You are aged 40 years or older.

Low dose aspirin may also be recommended if two or more of the following apply to you.

• This is your first pregnancy.

• There are more than 10 years between this pregnancy and the birth of your last baby.

• Your BMI is 35 or more at your booking appointment.

• There is a family history of pre-eclampsia in a first degree relative. A first degree relative includes a parent, a full sibling (sharing the same mum and dad), or a child.

• This is a multiple pregnancy (for example twins or triplets)

You may also be advised to take low dose aspirin if one or more of the following applies to you.

• You had a uterine artery Doppler ultrasound that shows high resistance. For more information, please read the Uterine artery Doppler ultrasound leaflet.

• You have a slightly higher chance of having a baby which may be smaller than expected.

• There were any concerns about how your placenta was working in a previous pregnancy.

If aspirin is recommended, your midwife or doctor will discuss this with you.

How and when do I take aspirin?

Take 150mg (2 x 75mg tablets) once a day from 12 weeks, until the birth of your baby. It is best to take in the evening either with or just after food.

Please do not worry if you forget to take a tablet, just take one when you remember. You must only take 150mg (2 x 75mg tablets) in one day.

If you think you may be in labour, you can stop taking your aspirin until this is confirmed. It will not increase your risk of bleeding during your labour.

Is low dose aspirin safe to take in pregnancy?

Low dose aspirin is not known to be harmful to you or your baby during pregnancy. In fact it is known to reduce the risk of harm by reducing the risk of:

• high blood pressure

• pre-eclampsia

• smaller babies, and

• stillbirth.

However, aspirin can affect (and be affected by) other medications. If you are taking over-the-counter medicines and / or herbal remedies, please tell your midwife or doctor.

What are the possible side effects?

• Taking low dose aspirin can cause mild indigestion. If you take your aspirin either with or just after food, it will be less likely to upset your stomach. Avoid taking aspirin on an empty stomach. If you also take indigestion remedies, take them at least two hours before or after you take your aspirin.

• There is no evidence to suggest low dose aspirin causes any increase in bleeding during pregnancy, or at the time of birth.

If you have any questions or concerns about taking low dose aspirin, please speak to your obstetrician, GP, or midwife.

What if I have any allergies?

Please tell your obstetrician, midwife, or GP if you:

• are allergic to aspirin (or other NSAIDS);

• have severe asthma;

• chronic kidney problems;

• stomach ulcers; or

• have been previously advised not to take aspirin or other NSAIDs.

As with any medicine, ask for urgent medical help if you have serious side effects, such as:

• wheezing

• swelling of the lips, face, or body

• rashes, or

• any other signs of an allergic reaction.

What can I do to help myself and my baby?

If you smoke it is very important that you stop, as it can affect placental (afterbirth) function and your baby’s growth. If you need support to stop smoking, please speak with your midwife or doctor. Maternity have a dedicated in-house stop smoking service.

You can also self-refer through One You Kent.

• One You Kent
  Telephone: 0300 123 1044
  Email

Who can I speak with if I need further information?

Please contact Maternity triage if you have any worries, concerns or further questions.

• Maternity Triage
  Telephone: 01227 206737 (Open Monday to Sunday, 24 hours a day)

Further information

If you would like more information about taking low dose aspirin in pregnancy, speak to your midwife or doctor. They will be happy to answer your questions and advise you.

• Best use of medicines in pregnancy (BUMPS)

• East Kent Hospitals. Low Pregnancy Associated Plasma Protein-A (Low PAPP-A) patient leaflet.

• East Kent Hospitals. Uterine artery Doppler ultrasound patient leaflet.

• NHS: low dose aspirin

[Web sites last accessed 19 February 2026]

Important information

The information in this leaflet is for guidance purposes only. It is not provided to replace professional clinical advice from a qualified practitioner.

This leaflet has been produced with grateful acknowledgement to East Sussex Healthcare NHS Trust.

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