Aspirin in pregnancy

Patient Experience

  • Reference Number: HEY1046/2022
  • Departments: Maternity Services
  • Last Updated: 12 January 2022


This leaflet has been produced to give you general information about your condition.  Most of your questions should be answered by this leaflet.  It is not intended to replace the discussion between you and your doctor/midwife, but may act as a starting point for discussion. If after reading it you have any concerns or require further explanation, please discuss this with a member of the healthcare team.

Why is aspirin given during 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 this group of women are at reduced risk of developing these conditions if they take a low dose of aspirin during their pregnancy.

Why do I need aspirin during my pregnancy?

If you have 1 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 disease during your previous pregnancy
  • Chronic kidney disease
  • Autoimmune disease such as systemic lupus erythematosus or antiphospholipid syndrome
  • Type 1 or Type 2 diabetes
  • Chronic hypertension
  • Low Pregnancy Associated Plasma Protein (PAPP-A) screening blood test
  • Previous Intrauterine growth restriction (IUGR) (either birth weight <2.5kg or <10th centile)
  • Previous stillbirth
  • Previous pre-eclampsia/eclampsia

If you have 2 of the following risk factors you will be offered aspirin during your pregnancy:

  • First pregnancy
  • Pregnancy interval of more than 10 years
  • Family history of pre-eclampsia
  • IVF pregnancy
  • Age 40 years or older
  • Multiple pregnancy
  • Body Mass index (BMI) of 35Kg/m2 or more at first contact

How much aspirin do I need to take?

Take 150mg once a day, ideally at the same time every day. You will usually be given a pack of 75mg tablets. You will need to take TWO of these tablets to achieve your 150mg dose. However, always check the strength of the preparation you are given by your GP or community pharmacy. If you take your aspirin either with or just after food, it will be less likely to upset your stomach.

When should I take?

We recommend you take 150mg of Aspirin every night from the 12th week of pregnancy until delivery of your baby. Aspirin (like many other medication) is not licensed for use in pregnancy. It does not mean it is not safe to use. When a medication is used ‘off-license’, it is used in the context of a well-reasoned medical recommendation.

What are the side effects?

  • Mild indigestion is a common side effect and is known to affect 1 in 100 people. If you take your aspirin either with or just after food, it will be less likely to upset your stomach. If you also take indigestion remedies, take them at least two hours before or after you take your aspirin.
  • As with any medicine, you should seek urgent medical assistance if you experience serious side effects such:
  1. Wheezing
  2. Swelling of the lips, face or body
  3. Rashes
  4. Severe stomach pains
  5. Vomiting blood
  6. Passing blood in your stools

There is no evidence to suggest low dose aspirin causes any increase in vaginal 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.

Are there any contraindications to taking aspirin?

If you have any of the conditions below we would not recommend taking aspirin during your pregnancy:

Allergic to aspirin (or other NSAIDS); Severe asthma; Chronic kidney problems;  Have been previously advised not to take aspirin or other NSAIDs; Active peptic ulceration; Bleeding disorders (antiplatelet dose); Children under 16 years (risk of Reye’s syndrome); Haemophilia; Severe cardiac failure. Your doctor will advise you if this applies to you.

How will I receive the prescription?

Most risk factors will be identified by your midwife at your first booking appointment. The midwife will send a letter to your doctor to request the prescription which you can collect from your doctor’s surgery.

Some risk factors may be identified later in your pregnancy, for example following an ultrasound scan. If this is the case your midwife or doctor will inform you at that time and will receive the prescription from your doctor. You will need to take Aspirin as soon as you have received the prescription if it is later than 12 weeks.

Should you require further advice on the issues contained in this leaflet, please do not hesitate to contact:

Antenatal Clinic (01482) 382623

Community Midwives (01482) 382658 / 382742


Under the General Data Protection Regulation and the Data Protection Act 2018 we are responsible for maintaining the confidentiality of any information we hold about you. For further information visit the following page: Confidential Information about You.

If you or your carer needs information about your health and well-being and about your care and treatment in a different format, such as large print, braille or audio, due to disability, impairment or sensory loss, please advise a member of staff and this can be arranged.

This leaflet was produced by the Maternity Services, Hull University Teaching Hospitals NHS Trust and will be reviewed in February 2025.

Ref: HEY1046/2020 

Further Information:

NHS website:

The Royal College of Obstetricians & Gynaecologists: leaflets/pregnancy/pi-having-a-small-baby.pdf leaflets/pregnancy/pi-pre-eclampsia.pdf

Saving babies Lives Care Bundle. NHS England 2019: a-care-bundle-for-reducing-perinatal-mortality/

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