Low Dose Aspirin

Last Update: 08 Apr 2025

Medication

Table of content

1. What is it? 2. What are the risks? 3. Breastfeeding/ chestfeeding 4. Fathers and sperm donors 5. Key points

Welcome to our fact sheet on low dose aspirin during pregnancy and breastfeeding/ chestfeeding This information is based on available published literature. It should not take the place of medical care and advice from your healthcare provider.

The HEALTHY PREGNANCY HUB team is collaborating with MotherToBaby to share information on this topic. The original version is available here (updated on February 2024).

Serene, our chatbot, can also answer your questions about medications during pregnancy.

Please note that this fact sheet is based on United States information and has been adapted for Canada, with a review by our Canadian experts. Minor differences may exist between the two countries. Always consult your healthcare professional for information tailored to your situation.

1. What is it?

What is aspirin?

Aspirin is also known as acetylsalicylic acid and has been used to reduce inflammation, fever, and pain. Aspirin can prevent blood clots and has been used to treat or help prevent conditions like heart attack and stroke. Aspirin is part of a group of drugs called non-steroidal anti-inflammatory drugs (NSAIDs).

NSAIDs, including regular and high strength aspirin, are NOT preferred pain relievers during pregnancy. In October 2020, the U.S. Food and Drug Administration (FDA) made a recommendation to avoid the use of NSAIDs, including regular strength aspirin, after 20 weeks of pregnancy, unless your healthcare provider feels it is necessary.This recommendation does not apply to low dose aspirin. More information about regular strength aspirin can be found in our fact sheet here.

What is low dose aspirin?

Low dose aspirin ranges from 60 to 150 mg daily, but the usual dose taken during pregnancy to treat or prevent certain conditions is 81 mg daily.

Sometimes when people find out they are pregnant, they think about changing how they take their medication, or stopping their medication altogether. However, it is important to talk with your healthcare providers before making any changes to how you take your medication. Your healthcare providers can talk with you about the benefits of treating your condition and the risks of untreated illness during pregnancy.

Discover our video about aspirin to prevent preeclampsia.

Learn more

2. What are the risks according to research?

I take low dose aspirin. Can it make it harder for me to get pregnant?

Low dose aspirin is not expected to make it harder to get pregnant. A study that included individuals who had one or two previous pregnancy losses found that taking low dose aspirin at least 4 days a week increased the chance of pregnancy.

Does taking low dose aspirin increase the chance of miscarriage?

Miscarriage is common and can occur in any pregnancy for many different reasons. Taking low doses of aspirin as directed by a healthcare provider is not expected to increase the chance of miscarriage. Some studies have shown that taking low dose aspirin before pregnancy might help lower the chance of miscarriage in some people who have had one or more miscarriages before 20 weeks of pregnancy.

Does taking low dose aspirin increase the chance of birth defects?

Every pregnancy starts out with a 3-5% chance of having a birth defect. This is called the background risk. Studies on the use of low dose aspirin during pregnancy have not found a higher chance of birth defects.

Does taking low dose aspirin in pregnancy increase the chance of other pregnancy-related problems?

Taking low dose aspirin as directed by a healthcare provider is not expected to increase the chance of pregnancy-related problems, such as preterm delivery (birth before week 37) or low birth weight (weighing less than 5 pounds, 8 ounces [2500 grams] at birth).

Studies have shown that low dose aspirin might improve pregnancy outcomes in some individuals by increasing blood flow to and reducing inflammation or swelling in the uterus. It may also lower the chances for preterm delivery and preeclampsia (high blood pressure and problems with organs, such as the kidneys), which can lead to seizures (called eclampsia) in individuals who have a higher risk of these complications. However, pregnant individuals should only take low dose aspirin under the direction and care of their healthcare provider.

Does taking low dose aspirin in pregnancy affect future behavior or learning for the child?

Limited information on low dose aspirin exposure during pregnancy does not suggest an increased chance for problems with physical or mental development in infants at 18 months of age. A study that looked at children up to 5 years of age who were born before 33 weeks of pregnancy and who were exposed to low dose aspirin during pregnancy did not find an effect on learning or behavior compared to children who were not exposed to low dose aspirin during pregnancy. Another study found no differences in neurodevelopmental outcomes in children between 33 and 39 months old after prenatal exposure to low dose aspirin.

3. Breastfeeding/ chestfeeding while taking low dose aspirin

Low dose aspirin gets into breast milk/ human milk in small amounts. Occasional use of low dose aspirin is not expected to increase risks to a breastfeeding/ chestfeeding infant. Regular strength aspirin (over 325 mg) is not preferred during breastfeeding/ chestfeeding. More information about regular strength aspirin can be found in our fact sheet here. Be sure to talk to your healthcare provider about all your breastfeeding/ chestfeeding questions.

Discover our fact sheet on regular strength aspirin!

Learn more

4. Fathers and sperm donors

If a male takes low dose aspirin, could it affect fertility or increase the chance of birth defects?

It is not known if low dose aspirin could affect a male’s fertility (ability to get a partner pregnant) or increase the chance of birth defects above the background risk. In general, exposures that fathers and sperm donors have are unlikely to increase risks to a pregnancy. For more information, please see the MotherToBaby fact sheet on Paternal Exposures here.  

Key points

Low-dose aspirin (60–150 mg per day, typically 81 mg) is used during pregnancy to prevent certain health problems such as preeclampsia, but only under medical supervision. Regular strength aspirin (more than 325 mg) is usually not recommended.
Studies have not shown an increased risk of miscarriage, birth defects, or other pregnancy complications with the use of low-dose aspirin.
Low-dose aspirin passes into breast milk/ human milk in small amounts and is not expected to pose a risk to a baby.
Low-dose aspirin, like other nonsteroidal anti-inflammatory drugs (NSAIDs), should be used under the supervision of a healthcare professional during pregnancy.

References

Please click here for references.

Disclaimer

HEALTHY PREGNANCY HUB provides a source of information validated by health professionals; however, this information is provided for informational purposes only and should not replace professional advice. Medical standards and practices evolve as new data becomes available, so it is imperative to consult your doctor or a qualified health professional for any questions or concerns regarding your health without delay or omission. It is the responsibility of your treating physician or any other health professional, based on their independent experience and knowledge of the patient, to determine the best way to evaluate and treat you.

HEALTHY PREGNANCY HUB does not specifically recommend or endorse any test, practitioner, treatment, product, or opinion mentioned on our platform. HEALTHY PREGNANCY HUB also does not replace the individual patient assessment based on the examination by the healthcare provider of each patient and the consideration of laboratory data and other patient-specific factors.

The use of the information available on our site is at your own risk. No person involved in the creation, production, promotion, or marketing of HEALTHY PREGNANCY HUB guarantees or represents, expressly or implicitly, anything regarding the information available on the platform, which is provided “as it is”. All warranties are expressly excluded and disclaimed, including but not limited to implied warranties of merchantability or fitness for a particular purpose, as well as any warranties arising by law or otherwise in law or from trade or usage. Any statements or representations made by any other person or entity are void.

While consulting symptoms or other medical information on our platform may guide your discussions with your healthcare professional, this information should not be used to make a medical diagnosis or determine treatment. Before making changes to your supplement or medication regimen, please discuss with your medical team or contact 811 (Canada) to ensure the relevance of these changes to your individual situation.

Credits