- There is an important difference between prescribed low-dose aspirin and taking regular-strength aspirin for pain, and the guidance is not the same for both.
- For people at increased risk of preeclampsia, ACOG and the USPSTF support daily low-dose aspirin, usually started in the second trimester and continued until delivery, when a clinician recommends it.
- The FDA advises avoiding NSAIDs (which include full-dose aspirin) from about 20 weeks of pregnancy, but says this does not apply to low-dose 81 mg aspirin prescribed for certain conditions.
- Regular-strength aspirin used as a general pain reliever is usually not the preferred choice in pregnancy, especially later on.
- Do not start or stop low-dose aspirin on your own; if it was prescribed, keep taking it as directed unless your clinician says otherwise.
- MotherToBaby (1-866-626-6847) can answer questions about a specific medication exposure in pregnancy.
Aspirin is one of those medicines that means two different things in pregnancy, and confusing the two causes a lot of worry. A prescribed daily low-dose aspirin, used to lower the chance of certain pregnancy complications, is not the same as reaching for a regular-strength aspirin tablet for a headache. This article explains what leading U.S. sources say about each, so you can have a clearer conversation with the clinician who manages your pregnancy. It is general education only and is not a substitute for that conversation.
Two very different uses of “aspirin”
Aspirin is a nonsteroidal anti-inflammatory drug (NSAID), and it also thins the blood slightly by affecting platelets. In pregnancy, the word “aspirin” usually refers to one of two very different things: a small daily dose (commonly 81 mg in the U.S., often called low-dose or “baby” aspirin) taken to reduce the risk of preeclampsia in people who are at higher risk, or a regular full-strength dose taken occasionally as a pain reliever or fever reducer. Because the doses, purposes, and guidance differ, it is worth keeping them separate in your mind and in any conversation with your provider.
Low-dose aspirin under medical direction
The American College of Obstetricians and Gynecologists (ACOG) and the U.S. Preventive Services Task Force (USPSTF) support daily low-dose aspirin for pregnant people who are at increased risk of preeclampsia, a serious pregnancy condition involving high blood pressure. In this setting, low-dose aspirin is generally started in the second trimester, often between about 12 and 28 weeks and ideally before 16 weeks, and continued daily until delivery when a clinician recommends it. ACOG describes the maternal and fetal risks of low-dose aspirin in this context as low, and the evidence base as reassuring. Importantly, this is a treatment a clinician recommends after weighing your individual risk factors, such as a prior history of preeclampsia, chronic high blood pressure, certain kidney or autoimmune conditions, or carrying more than one baby. It is not something to start on your own based on general reading.
What the FDA says about NSAIDs, and the low-dose exception
Separately, the FDA advises avoiding NSAIDs from about 20 weeks of pregnancy onward unless a clinician specifically recommends them, because around this stage NSAIDs can reduce the baby’s urine output and lower the level of amniotic fluid (a condition called oligohydramnios) and can affect the developing kidneys. Later in pregnancy there is an additional concern that NSAIDs can cause a fetal blood vessel, the ductus arteriosus, to narrow or close too early. Full-strength aspirin belongs to the NSAID family, so these cautions are relevant to using regular aspirin as a pain reliever. Crucially, the FDA states that this recommendation does not apply to low-dose 81 mg aspirin prescribed for certain conditions in pregnancy. In other words, the later-pregnancy NSAID warning and prescribed low-dose aspirin are two different situations.
Regular-strength aspirin for pain
Using regular full-dose aspirin simply as a general pain or fever reliever is usually not the preferred approach in pregnancy, particularly in the later trimesters, given the NSAID concerns above and aspirin’s blood-thinning effect around the time of delivery. If you need something for pain or fever, that is a good question to bring to your clinician rather than deciding at the pharmacy shelf, because untreated fever and significant pain also deserve appropriate treatment. The choice, and the safest option for you, depends on how far along you are and your health history.
A note on old drug “categories”
Older leaflets sometimes quote the FDA’s A/B/C/D/X pregnancy letter categories. Those letter grades have been retired. The FDA now uses a narrative labeling approach, sometimes called the Pregnancy and Lactation Labeling Rule (PLLR), that summarizes the actual evidence rather than assigning a single letter. If you see a letter grade quoted for aspirin, treat it as outdated and rely on current guidance and your clinician.
The other side: untreated conditions matter too
It is worth remembering that the whole reason low-dose aspirin is recommended for some people is that preeclampsia itself is a real and serious risk. Caution about medicines is not the same as avoiding all treatment. If your clinician has recommended low-dose aspirin, its purpose is to lower a meaningful risk, and stopping it on your own could remove that protection. As always, the goal is the right treatment for your situation, which is a decision to make with your care team.
Breastfeeding
MotherToBaby reports that low-dose aspirin is generally considered compatible with breastfeeding, while higher analgesic doses are less preferred and other pain relievers are often suggested instead. If you are breastfeeding and have questions about aspirin at any dose, confirm the specifics with your clinician, especially for a newborn or a baby with health concerns.
Do not start or stop on your own
Two principles are worth holding onto. First, do not start daily low-dose aspirin in pregnancy on your own; it is recommended based on individual risk factors that your clinician assesses, and it is not right for everyone. Second, if low-dose aspirin was prescribed to you, do not stop it abruptly without discussing it with the prescriber, because it was started for a reason and the plan usually runs until delivery. Likewise, do not use full-strength aspirin as a routine pain reliever in pregnancy without checking first. The right answer is individualized.
When to call your OB or a specialist
Reach out to your obstetric provider to ask whether low-dose aspirin is appropriate for you, and promptly if you notice signs that can be associated with preeclampsia later in pregnancy, such as severe or persistent headache, vision changes, upper abdominal pain, or sudden swelling. Tell your provider about any aspirin use before a procedure or delivery because of its effect on bleeding. For a complex situation, your provider may involve a maternal-fetal-medicine specialist. For questions about a specific medication exposure, you can call MotherToBaby at 1-866-626-6847, a free service.
Frequently asked questions
Is low-dose “baby” aspirin safe in pregnancy? When a clinician recommends it for someone at increased risk of preeclampsia, ACOG and the USPSTF support daily low-dose aspirin and describe the risks as low. It should be taken as directed, not started on your own.
Why does the FDA warn about aspirin after 20 weeks? That warning is about NSAIDs used as pain relievers, including full-strength aspirin, because of concerns about amniotic fluid and the baby’s kidneys and heart. The FDA says it does not apply to prescribed low-dose 81 mg aspirin.
Can I take a regular aspirin for a headache while pregnant? Regular-strength aspirin is generally not the preferred pain reliever in pregnancy, especially later on. Ask your clinician what is appropriate rather than taking it on your own.
When is low-dose aspirin usually started and stopped? When recommended, it is generally started in the second trimester, often before 16 weeks, and continued daily until delivery. Your clinician sets the timing for your situation.
I took aspirin before I knew I was pregnant. Should I worry? Let your OB know what dose you took and when. Early exposure is a common concern, and MotherToBaby and your provider can help put a specific exposure in context.
Is low-dose aspirin okay while breastfeeding? MotherToBaby reports that low-dose aspirin is generally considered compatible with breastfeeding, while higher doses are less preferred. Confirm the details with your clinician.
This article is general education, not medical advice, and must not be used to start, stop, adjust, or taper any medication on your own. Suddenly stopping some medicines can be dangerous. Always work with the prescriber who manages your care. In an emergency call 911; for mental-health crisis call or text 988.
Sources
- American College of Obstetricians and Gynecologists (ACOG) — Low-Dose Aspirin Use During Pregnancy (Committee Opinion 743).
- U.S. Food and Drug Administration — Drug Safety Communication on avoiding NSAIDs in pregnancy at 20 weeks or later, including the low-dose 81 mg aspirin exception.
- U.S. Preventive Services Task Force (USPSTF) — Aspirin Use to Prevent Preeclampsia and Related Morbidity and Mortality.
- MotherToBaby (Organization of Teratology Information Specialists) — Aspirin fact sheet.