Low dose aspirin in pregnancy

Key points about low dose aspirin in pregnancy

  • Some pregnant people are at risk of developing a serious high blood pressure condition called pre-eclampsia.
  • If you're at risk of pre-eclampsia, taking a low dose of aspirin every day during pregnancy reduces your risk and increases your chance of having a healthy baby.
  • Aspirin may also be recommended if you have had a very small baby, or heavy bleeding in a previous pregnancy caused by the placenta detaching from the womb (uterus).
  • Find out how to take it safely and possible side effects.
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Aspirin is known as an NSAID (a non-steroidal anti-inflammatory drug). Low strengths or doses of aspirin are often used to reduce blood clotting in people who have heart disease. For pregnant people who are at risk of pre-eclampsia, or at risk of having a low birth weight baby, taking low dose aspirin once a day during pregnancy can help increase blood flow in your placenta (afterbirth). Your placenta provides your baby with oxygen and nutrients during your pregnancy to help them grow. Read more below about when aspirin is given during pregnancy.

Note: Calcium has also been found to be helpful for pregnant people who are at risk of developing preeclampsia. Your obstetrician will also prescribe calcium if they believe it's needed. Read more about calcium supplements in pregnancy.

Low-dose aspirin is used from 12 weeks of pregnancy, mainly to prevent pre-eclampsia in women you are at increased risk of developing pre-eclampsia. Pre-eclampsia is a condition in pregnancy that can result in you and your baby becoming seriously ill. One of the common symptoms is high blood pressure. Read more about pre-eclampsia.

Risk factors for pre‑eclampsia

The chance of developing pre-eclampsia is higher if you have:

  • certain medical conditions such as high blood, diabetes, kidney disease, antiphospholipid antibodies or systemic lupus erythematosus (SLE)
  • had pre-eclampsia before
  • a sister or mother who had pre-eclampsia
  • had in vitro fertilisation (IVF)

Low-dose aspirin may also be recommended if you have had a previous pregnancy with foetal growth restriction (a very small baby) or heavy bleeding caused by the placenta detaching from the womb. Foetal growth restriction (FGR) is a condition in which an unborn baby (fetus) is smaller than expected for the number of weeks of pregnancy (gestational age).

  • Low dose aspirin is the coated aspirin (100 mg) tablet. 
  • The dose is 1 tablet once a day.
  • Swallow the tablet whole with a glass of water. Don't crush or chew it as this affects the special coating.
  • It doesn't matter if you take the coated aspirin tablets with or without food.

Your obstetrician will tell you how long to take aspirin for. It's usually started as early in your pregnancy as possible and continued until you are 36 to 37 weeks pregnant.

Do not take aspirin if:

  • you are allergic to aspirin.
  • you have ever had a stomach ulcer.
  • taking pain relief medicines gives you asthma symptoms.

Low dose aspirin is not known to be harmful to you or your baby during pregnancy.

  • It shouldn't cause any increase in bleeding during pregnancy or at the time of birth.
  • Taking low dose aspirin doesn't change any of your choices for pain relief in labour. You can stop taking your low dose aspirin when your baby is born.

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

Taking low dose aspirin can cause mild indigestion. It's best to take your aspirin either with or just after food, so it's less likely to upset your stomach. Avoid taking aspirin on an empty stomach. If you also take indigestion remedies, take them at least 2 hours before or after you take your aspirin.

As with any medicine, you should seek urgent medical assistance if you experience serious side effects.

Serious side effects include:

  • wheezing
  • swelling of your lips, face or body
  • rashes
  • other signs of an allergic reaction.

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Link to Māori Pharmacists website

Credits: Sandra Ponen, Healthify Pharmacist. Healthify is brought to you by Health Navigator Charitable Trust.

Reviewed by: Angela Lambie, Pharmacist, Auckland

Last reviewed: