This sheet talks about exposure to low dose aspirin in a pregnancy or while breastfeeding. This information should not take the place of medical care and advice from your healthcare provider.

What is low dose aspirin?

Aspirin is also known as acetylsalicylic acid (pronounced uh-seet-l-sal-uh-sil-ik). It is a common prescription and over-the-counter medication that is similar to non-steroidal inflammatory (NSAIDs) like ibuprofen (Motrin®) and naproxen (Aleve®). Aspirin reduces inflammation, fever and pain. Aspirin can prevent the formation of blood clots which can make it useful in treating or preventing some conditions like heart attacks and strokes. The dosage for aspirin can range from 50 to 6000 milligrams (mg) per day depending on the condition being treated. Aspirin can also be used in combination with other medications. Low dose aspirin ranges from 60 to 150 mg daily but the usual dose taken during pregnancy is 81 mg daily.

Regular strength aspirin is NOT a preferred pain reliever during pregnancy.

Can taking low dose aspirin during pregnancy increase the chance of a miscarriage?

Taking low doses of aspirin is not thought to increase the chance of miscarriage. Some studies have shown that low dose aspirin can lower the chance of miscarriage in some women.

Most studies have looked at women who started using aspirin after becoming pregnant, but the results from a few other studies suggest that using low dose aspirin before conceiving may help improve pregnancy outcomes among women who have had one or more previous miscarriage before 20 weeks of pregnancy. These findings are similar to studies that showed improved pregnancy outcomes for women who were undergoing assisted reproduction technologies and were treated with low dose aspirin prior to implantation of the fertilized egg into the uterus.

Can taking low dose aspirin increase the chance of birth defects during pregnancy?

In every pregnancy, a woman starts out with a 3-5% chance of having a baby with a birth defect. This is called her background risk. Studies have shown that taking low dose aspirin does not increase the chance for birth defects. Some studies have shown increased risk for having a baby with a birth defect when women have taken high doses of aspirin. However, low dose aspirin is considered compatible in all trimesters of pregnancy when medically needed.

I heard that low dose aspirin can be recommended during pregnancy? Why?

For some women, it is thought that low dose aspirin could improve pregnancy outcomes by increasing blood flow and reducing inflammation or swelling in the uterus. Results from many studies have shown that the use of low dose aspirin can lower the chances for preeclampsia in women who are at high risk for this condition. Preeclampsia may be diagnosed when a woman develops dangerously high blood pressure and protein in the urine. Preeclampsia can lead to serious health problems for both mom and baby, including preterm birth and low birth weight.

Many health organizations including American Congress of Obstetrician and Gynecologists (ACOG), the World Health Organization (WHO), the American Heart Association (AHA) and the American Academy of Family Physicians (AAFP) have recommended treatment with low dose aspirin for women at high risk for preeclampsia from at least 12 weeks of pregnancy until time of delivery. Only take low dose aspirin during pregnancy if your healthcare provider recommends it. 

Are there long term effects from taking low dose aspirin in pregnancy?

There are not many studies about long term effects for children exposed to low dose aspirin during pregnancy. However, studies have not found an increased risk for problems with physical or mental development for infants at 18 months of age. Another study that looked at children up to 5 years of age who were born very early (before 33 weeks) and who were exposed to low dose aspirin during pregnancy did not find an effect on learning or behavioral skills compared to unexposed children.

Can I take low doses of aspirin while I am breastfeeding?

Regular strength aspirin is not the pain reliever of choice during breastfeeding. However, the occasional use of low dose aspirin (75 mg daily to below 300 mg daily) would not be expected to increase risks to a breastfeeding infant. Only small amounts of low dose aspirin enter the breast milk.

There is some concern with the use of high dose aspirin since this medication can lower the body’s ability to clot blood and, in some cases where infection is present, cause liver damage to the baby. These effects are not likely with low dose aspirin but aspirin eliminates from the infant body more slowly than from an adult’s body, so levels in the infant’s body could increase over time with long term use. For some women, treatment with low dose aspirin may be recommended by your healthcare provider.

What if the father of the baby is taking low doses of aspirin?

There is very limited information available about the effects of low dose aspirin on male reproduction. There was a study on men who attended an infertility clinic and were taking non-prescribed low dose aspirin for at least six months. There was a decrease in the amount and quality of sperm especially for those who used higher amounts of aspirin. Presently, it is not considered necessary for men to discontinue the use of low dose aspirin prior to pregnancy. However, men undergoing fertility treatment may want to talk with their healthcare provider about stopping aspirin if their semen analysis is abnormal. In general, exposures that fathers have are unlikely to increase risks to a pregnancy. For more information, please see the MotherToBaby fact sheet on Paternal Exposures and Pregnancy at

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