June 1, 2026
Benefits of Low-Dose Aspirin
A new study led by physician-researchers at Beth Israel Deaconess Medical Center suggests that low-dose aspirin may reduce preterm births in extreme heat climates. Increased heat exposure during pregnancy was associated with higher odds of preterm birth, but not among those who took low-dose aspirin starting early in pregnancy.
Low-dose aspirin is already a proven intervention for reducing preeclampsia risk. It has been routinely recommended by the American College of Obstetricians and Gynecologists (ACOG) and the U.S. Preventive Services Task Force (USPSTF) in women at high risk of preeclampsia. More specifically, low dose aspirin should be initiated at 12 weeks of gestation if a patient has at least on high-risk factor (history of preeclampsia, chronic hypertension, multifetal gestation, diabetes, renal disease, autoimmune disease) or more than one moderate-risk factor (first pregnancy, age ≥35-years-old, IVF, obesity, previous adverse pregnancy outcome, more than 10-year pregnancy interval, family history of preeclampsia, sociodemographic characteristics).
International guidelines lack consensus on the optimal aspirin dose for preeclampsia prevention. A randomized control trial addressing aspirin dosing (ASPRE Trial) found that 150 mg aspirin was associated with a significant risk reduction in preterm delivery due to preeclampsia. Most European studies have used 150 mg; however, in the United States, the most readily available dose over 100 mg is 162 mg (2 tabs of aspirin 81 daily). Neither ACOG nor SMFM (Society for Maternal-Fetal Medicine) have yet to endorse a higher dose of aspirin for the prevention of preeclampsia; however, emerging evidence from newer studies in the United States increasingly supports 162 mg as the optimal dose for preeclampsia prevention.
-Michelle Nguyen, MD
References:
Meltzer GY, Duttweiler LP, Saleem S, et al. Aspirin and preterm birth among pregnant people with increased heat exposure: secondary analysis of a randomized clinical trial. JAMA Netw Open. 2026;9(5):e2611402. https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2848672
ACOG Committee Opinion #743: Low-Dose Aspirin Use During Pregnancy. https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2018/07/low-dose-aspirin-use-during-pregnancy
ACOG Practice Advisory: Low-Dose Aspirin Use for the Prevention of Preeclampsia and Related Morbidity and Mortality. https://www.acog.org/clinical/clinical-guidance/practice-advisory/articles/2021/12/low-dose-aspirin-use-for-the-prevention-of-preeclampsia-and-related-morbidity-and-mortality
Rolnik DL, Wright D, Poon LC, et al. Aspirin versus placebo in pregnancies at high risk for preterm preeclampsia. N Engl J Med. 2017;377(7):613-622. https://www.nejm.org/doi/full/10.1056/NEJMoa1704559
Jones Pullins ME, Boggess KA. Aspirin dosage for preeclampsia prophylaxis: an argument for 162-mg dosing. American Journal of Obstetrics & Gynecology MFM. 2025;7(1):101620. https://www.ajogmfm.org/article/S2589-9333(25)00021-7/abstract
