This sheet is about exposure to regular strength aspirin in pregnancy and while breastfeeding. This information is based on published research studies. It should not take the place of medical care and advice from your healthcare provider.
What is regular strength aspirin?
Aspirin, also known as acetylsalicylic acid, has been used to treat inflammation, fever, and pain. It has also been used to prevent blood clots. Aspirin belongs to the class of medications called non-steroidal anti-inflammatory drugs (NSAIDs). It is available over the counter and by prescription. A single tablet of regular strength aspirin is 325mg. This sheet will focus on the use of more than 325mg of aspirin in a 24-hour period.
Low dose aspirin is sometimes used in pregnancy for different reasons. The pregnancy information for low dose aspirin is different. MotherToBaby has a fact sheet on low dose aspirin here: https://mothertobaby.org/fact-sheets/low-dose-aspirin/.
The U.S. Food and Drug Administration (FDA) recommends not using NSAIDs after 20 weeks of pregnancy, unless your healthcare provider specifically recommends it.
I take regular strength aspirin. Can it make it harder for me to get pregnant?
Some studies suggest that using regular strength aspirin or other NSAIDs might make it harder to get pregnant. This might be more likely when NSAIDs are used over a long period of time.
Does taking regular strength aspirin increase the chance of miscarriage?
Miscarriage is common and can occur in any pregnancy for many different reasons. An increased chance of miscarriage has been reported with the use of regular strength aspirin, especially with use around the time of conception.
Does taking regular strength aspirin increase the chance of birth defects?
Birth defects can happen in any pregnancy for different reasons. Out of all babies born each year, about 3 out of 100 (3%) will have a birth defect. We look at research studies to try to understand if an exposure, like regular strength aspirin, might increase the chance of birth defects in a pregnancy.
Most studies on the use of regular strength aspirin do not show an increased chance of birth defects. A few small studies have reported an increased chance of gastroschisis (opening in the stomach wall of the fetus) with early pregnancy use of regular strength aspirin.
Does taking regular strength aspirin in pregnancy increase the chance of other pregnancy-related problems?
Regular strength aspirin is generally not recommended for use after week 20 of pregnancy.
There are some studies that suggest NSAIDs can increase the chance of other 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. Other studies have not reported these findings. There can also be an increased chance for issues such as bleeding during pregnancy, bleeding after delivery (post-partum hemorrhage), and bleeding in the brain of the newborn with the use of regular strength aspirin in pregnancy.
Some reports suggest that NSAID use in the 2nd half of pregnancy might affect the fetal kidneys and the amount of amniotic fluid (fluid that surrounds the fetus in the uterus). One study suggested that the use of NSAIDS in the 1st half of pregnancy might also affect the fetal kidneys and amount of amniotic fluid. If there is not enough amniotic fluid (called oligohydramnios), other pregnancy complications, such as poor lung development and joint contractures (joints can become stiff or unable to move), could happen. Oligohydramnios can also increase the chance that an early delivery is needed. In some cases, oligohydramnios could cause fetal demise.
Regular strength aspirin use later in pregnancy might also cause premature closure of the ductus arteriosus (an opening between the two major blood vessels leading from the heart). If the ductus arteriosus closes before it should, it can cause high blood pressure in the fetal lungs (pulmonary hypertension).
Regular strength aspirin should only be used under a healthcare provider’s supervision, particularly in the 2nd and 3rd trimesters. Your healthcare providers can closely monitor your pregnancy if you need to use regular strength aspirin after week 20.
Does taking regular strength aspirin in pregnancy affect future behavior or learning for the child?
Some studies have shown an increase in newborn bleeding, including bleeding in the brain, from the use of regular strength aspirin during pregnancy. This might affect future brain development.
Breastfeeding while taking regular strength aspirin:
Aspirin passes into breast milk and is broken down by an infant’s body more slowly than in an adult’s body. This means aspirin levels in the infant’s body could build up over time. High doses of aspirin can lower the body’s ability to clot blood (could lead to easier bruising or bleeding). Reye’s syndrome, a rare condition involving brain swelling and liver damage, can be caused by giving aspirin to an infant while they are recovering from a viral infection such as a cold, the flu, or chickenpox. The same risk has not been reported when a baby is exposed to aspirin through breast milk. If you suspect the baby has any symptoms (bleeding or bruising), contact the child’s healthcare provider. Be sure to talk to your healthcare provider about all your breastfeeding questions.
If a male takes regular strength aspirin, could it affect fertility or increase the chance of birth defects?
Studies have not been done to see if regular strength aspirin could affect men’s fertility (ability to get a partner pregnant) or increase the chance of birth defects. In general, exposures that fathers or sperm donors have are unlikely to increase risks to a pregnancy. For more information, please see the MotherToBaby fact sheet Paternal Exposures at https://mothertobaby.org/fact-sheets/paternal-exposures-pregnancy/.
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