PERINATOLOGY.comInformation for you about your pregnancy
Patient Handout

Low-Dose Aspirin in Pregnancy

Helping lower the chance of preeclampsia

Preeclampsia is high blood pressure in pregnancy that can also affect the liver, kidneys, brain, placenta, or other organs.

For some people, 81 mg of aspirin each day can lower the chance of preeclampsia.

This is called low-dose aspirin. Take it only if your care team tells you to.

About 15% lower risk

In higher-risk pregnancies, aspirin lowered the chance of this problem by about 15%. Your own benefit depends on your risk.

Dose81 mg each day
Start12 to 28 weeks
Best startBefore 16 weeks
StopAt delivery

Who should take low-dose aspirin?

Your doctor will usually recommend it if you have one high-risk factor:

  • preeclampsia in a past pregnancy.
  • twins or more babies.
  • high blood pressure before pregnancy.
  • type 1 or type 2 diabetes.
  • kidney disease.
  • lupus or APS (an immune blood-clotting problem).

Who else may benefit?

Aspirin may also be used if you have two or more other risk factors:

  • first pregnancy.
  • BMI over 30 before pregnancy.
  • mother or sister had preeclampsia.
  • age 35 or older.
  • IVF pregnancy.
  • more than 10 years since a prior pregnancy.
  • some problems in a past pregnancy.
  • lower income.

Black patients may also be offered aspirin because social and health conditions can raise their risk of preeclampsia.

When should I start and stop?

Start: between 12 and 28 weeks. If possible, start before 16 weeks.

Stop: Keep taking it until delivery unless your care team says to stop.

Is low-dose aspirin safe?

Low-dose aspirin has been well studied. It is safe for the right patient when prescribed by a care team.

Studies did not show a clear rise in serious bleeding.

Low-dose aspirin alone usually does not keep you from having an epidural.

Tell your care team before taking it if...

  • you are allergic to aspirin or similar pain medicine.
  • aspirin has caused an asthma attack.
  • you have active bleeding or a stomach ulcer.
  • you have a bleeding problem or serious liver disease.
  • you take a blood thinner.

What should I remember?

  • Aspirin lowers risk. It cannot prevent every case.
  • Take your other medicines as directed.
  • Keep all prenatal and blood pressure visits.
  • Do not take extra aspirin for pain unless your doctor says to.
Call your care team right away for a bad headache that will not go away, new vision problems, strong pain high in the belly, trouble breathing, or very high blood pressure.
Medical references
  1. American College of Obstetricians and Gynecologists (ACOG) and Society for Maternal-Fetal Medicine (SMFM). Low-Dose Aspirin Use for the Prevention of Preeclampsia and Related Morbidity and Mortality. Practice Advisory. December 2021; reaffirmed October 2022.
  2. Society for Maternal-Fetal Medicine. ACOG-SMFM Practice Advisory: Low-Dose Aspirin Use for the Prevention of Preeclampsia and Related Morbidity and Mortality.
  3. U.S. Preventive Services Task Force. Aspirin Use to Prevent Preeclampsia and Related Morbidity and Mortality: Preventive Medication. September 28, 2021. Grade B.
  4. ACOG. Low-Dose Aspirin Use During Pregnancy. Committee Opinion No. 743.

Evidence note: The USPSTF pooled analysis found RR 0.85 for preeclampsia, RR 0.80 for preterm birth, RR 0.82 for small-for-gestational-age/fetal growth restriction, and RR 0.79 for perinatal mortality in higher-risk pregnancies.