• Reference Number: HEY1046/2026
• Departments: Maternity Services
• Last Updated: 31 January 2026

Introduction

You have been given this leaflet because your midwife or doctor has identified that you may benefit from taking low-dose aspirin during your pregnancy. This leaflet provides clear information to support informed decision-making, explains why aspirin has been recommended, and outlines how responsibility for prescribing and supply is managed.

Why do I need to take Aspirin in pregnancy

Some pregnant women are at risk of developing pre-eclampsia (a serious condition which usually presents as high blood pressure and protein in the urine) and intrauterine growth restriction (when the baby is smaller than usual due to not growing at a normal rate in the womb). There is evidence to suggest that taking low-dose aspirin significantly reduces these risks, particularly when started early in pregnancy.

Is Aspirin safe to take in pregnancy

Low-dose aspirin has been extensively studied and is considered safe and effective when taken as recommended.

Aspirin is not licensed specifically for preventing pre-eclampsia; however, it is strongly recommended nationally and locally because evidence clearly shows benefit. This will be explained to you, and your understanding and decision will be documented in your maternity records.

Why do I need aspirin during my pregnancy?

Not everyone is recommended to take aspirin in pregnancy. You have been advised to take aspirin because specific risk factors have been identified during your care, which increase the likelihood of pre-eclampsia or placental complications. These include reducing the risk of:

• Developing high blood pressure and/or 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 you have one of the following risk factors you will be offered aspirin during your pregnancy:

(Your midwife/doctor will indicate which risk factor(s) apply to you)

• Hypertensive diseases of pregnancy in your previous pregnancy,
• that involves: Pregnancy induced hypertension, superimposed hypertension, preeclampsia, eclampsia, HELLP
• Chronic kidney disease
• Autoimmune disease such as systemic lupus erythematosus or antiphospholipid syndrome
• Type 1 or Type 2 diabetes
• Chronic hypertension
• Blood taken during your combined screening test has shown that your level of pregnancy associated with plasma protein-A (PAPP-A) is lower than expected
• You have previously given birth to a baby who was smaller than expected
• Previous IUGR (intrauterine growth restriction) or SGA (small for gestational age) (growth <10th centile)
• You have a histology report which suggests that during a previous pregnancy your placenta did not function as well as it should have done
• Previous stillbirth
• If you have two of the following risk factors you will be offered aspirin during your pregnancy:
• (Your midwife/doctor will indicate which risk factors apply to you)
• First pregnancy
• Body mass index (BMI) > 35 at booking/first contact
• Pregnancy interval of more than 10 years
• Family history of pre-eclampsia

Multiple birth pregnancy

• ð Age 40 years or older
• ð IVF pregnancy

Your obstetrician may also advise you to take low-dose aspirin for other reasons, which they will discuss with you.

How much do I need to take?

• Dose: 150 mg once daily at night
• Start: From 12 weeks of pregnancy
• Stop: At 36 weeks of pregnancy or when you give birth, whichever happens first

How should I take it?

• Take once daily, preferable in the evening
• Take it with food
• Aim to take it the same time each day

How will I receive the prescription?

Many women who are eligible to take aspirin will be identified at their booking appointment. Your midwife is responsible for ensuring that aspirin is arranged for you, either by prescription or direct supply following your dating scan, and you will receive your full allowance to cover the remainder of your pregnancy so that treatment is not interrupted. In some cases, aspirin may be provided directly by the antenatal clinic. If additional risk factors are identified later in pregnancy, your midwife or doctor will discuss this with you promptly and ensure aspirin is arranged without delay.

Are there any contraindications to taking aspirin?

• Aspirin is not suitable for everyone. Tell your midwife or doctor if you have:
• An allergy to aspirin or other anti-inflammatory medicines (NSAIDs)
• A history of stomach ulcers or gastrointestinal bleeding
• Severe liver or kidney disease
• Asthma that worsens with aspirin
• Any significant bleeding during pregnancy
• Any bleeding disorders such as haemophilia
• If bleeding occurs during pregnancy, the decision to continue aspirin will be reviewed on an individual basis, and this decision will be clearly discussed with you.
• There is no evidence to suggest low-dose aspirin causes any increase in bleeding during pregnancy or at the time of birth.

Possible side effects

Most women have no side effects. Occasionally, aspirin may cause:

• Indigestion or stomach discomfort
• Easy bruising or bleeding
• Wheezing or breathing difficulty (rare)

If you experience any concerning symptoms, you should contact your midwife promptly for advice.

Monitoring during pregnancy

Your midwife will:

• Monitor your blood pressure and urine regularly
• Check that you have started aspirin and are taking it as advised
• Ensure that any concerns, changes in risk, or questions you have are addressed and documented

Further information

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

Useful links:

http://www.medicinesinpregnancy.org/Medicine–pregnancy/Aspirin/

http://www.nhs.uk/medicines/low-dose-aspirin/