How low-dose aspirin can help prevent preeclampsia
June 4, 2025
You’ve likely heard of older people taking a baby aspirin every day to reduce their risk of heart attack or stroke. This is because aspirin thins the blood and helps prevent blood clots.
Generally, pregnant women are advised to avoid aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs). But for some patients with certain risk factors, taking a daily low-dose (baby) aspirin during pregnancy can help prevent or delay preeclampsia.
Preeclampsia is dangerously high blood pressure that can happen during pregnancy and in the weeks after delivery. It is a serious complication that can be life-threatening for the mother and baby. There is no effective treatment except delivery, which can result in developmental concerns for the baby if it is diagnosed before term.
Preeclampsia is thought to be related to an inflammatory reaction within the blood vessels that connect the walls of the uterus to the placenta – the tissue that nourishes the fetus. These changes happen quite early, well before any signs or symptoms can be seen. Baby aspirin can inhibit the inflammatory response, potentially preventing or delaying the onset of preeclampsia.
Taking full-strength aspirin during pregnancy can harm the baby. This is especially true during the second half of pregnancy, when these drugs can increase the risk of complications such as low amniotic fluid or heart and kidney problems in the baby.
While full-strength aspirin is generally 325 milligrams per dose, low-dose aspirin is only 81 milligrams in the U.S. The lower dose retains the anti-inflammatory properties of the drug without the potential side effects of full-strength aspirin. Research has shown that, when low-dose aspirin is started before 16 weeks of pregnancy, there can be significant reductions in severe preeclampsia.
Taking a daily low-dose aspirin does not guarantee that you will not develop preeclampsia. Women at high risk or with more than two moderate risk factors for preeclampsia should consider low-dose aspirin. Talk with your health care provider about whether taking baby aspirin might benefit your pregnancy.
Who might benefit from low-dose aspirin in pregnancy?
A lot more women than you might think! Your doctor may recommend you take baby aspirin if you have certain risk factors.
- Recommended if you have one or more high-risk factors, including:
- History of preeclampsia
- Multiple pregnancy, such as twins or triplets
- Kidney disease
- Autoimmune disease
- Type 1 or Type 2 diabetes
- Chronic hypertension
- Recommended if you have two or more moderate-risk factors, including:
- First pregnancy
- Maternal age of 35 years or older
- Body mass index greater than 30
- Family history of preeclampsia
- Limited access to health care
- Personal history factors, including some prior pregnancy complications
If you meet these criteria, your doctor may ask you to start taking daily low-dose aspirin between 12 weeks and 28 weeks of pregnancy, ideally before 16 weeks, and continue every day until delivery.
In 2023, the American College of Obstetricians and Gynecologists (ACOG) reaffirmed its 2018 Practice Advisory for this recommendation. The U.S. Preventive Services Task Force made a similar recommendation in 2021.
How do I take low-dose aspirin?
You can find low-dose aspirin sold over the counter at pharmacies and in most grocery and corner stores. You also can ask your doctor to write you a prescription if that is more affordable for you.
Many brands of low-dose aspirin are coated to be gentle on an empty stomach. If the pills cause nausea or an upset stomach, take them with food and plenty of water.
There are many brands of baby aspirin, and most have a picture of a heart on them. In the U.S., low-dose aspirin is 81 milligrams per dose. In other parts of the world, including Europe, the dose is higher. There is some evidence that 150 milligrams of aspirin a day may be more effective in preventing preeclampsia, but we’re still learning from these studies. Talk with your doctor about the dose that is best for you.
When can full-strength aspirin or another NSAID help in pregnancy?
Despite the potential risks of taking full-strength aspirin or other NSAIDs such as ibuprofen during the second half of pregnancy, there are a few situations when your health care provider may recommend it.
If you have a major injury, your health care provider will likely give you the green light to take an NSAID for a couple days to get you over the pain hump. Before 32 weeks of pregnancy, an NSAID called indomethacin might be recommended for a few select indications such as reducing the pain and inflammation of a uterine fibroid that is dying because its blood supply is no longer adequate. It might also be used along with other modalities to try to reduce contractions in very early preterm labor. If we do use indomethacin, we only use it for 48 hours to reduce the effect of the NSAID.
Who should not take baby aspirin during pregnancy?
There are some people who should never take aspirin, even if they have risk factors for pre-eclampsia. It’s a short list but an important one. You should not take aspirin, even low-dose aspirin, if you have:
- An allergy to aspirin or another NSAID
- Nasal polyps, as it may cause life-threatening breathing complications
- Aspirin- or NSAID-induced asthma
- History of gastrointestinal bleeding or ulcers
- A platelet-related bleeding disorder, such as Von Willebrand disease
Preeclampsia may not cause noticeable signs until your blood pressure spikes. Some women may have a headache, shortness of breath, swelling of the hands and face, pain under their lower right ribs, or vision changes. If you have signs of preeclampsia, notify your health care provider immediately.
Preeclampsia is a medical emergency for you and your baby. Taking a daily low-dose aspirin if you are at a high or moderate risk for preeclampsia is a simple way to help reduce the risk.
To talk with an expert about taking low-dose aspirin during pregnancy, make an appointment by calling 214-645-8300 or request an appointment online.
