What are the current recommendations regarding aspirin for the prevention of preeclampsia?
Low-dose aspirin reduces the risk of preeclampsia, preterm birth, and fetal growth restriction. This has been consistently shown in multiple systematic reviews and randomized trials.
Modern U.S. guidelines (ACOG & SMFM) recommend low-dose aspirin 81 mg daily for individuals at increased risk of preeclampsia, starting between 12–28 weeks (ideally before 16 weeks) and continuing until delivery.
U.S. (ACOG / SMFM) Recommendation
- 81 mg aspirin daily
- Begin: 12–28 weeks (best before 16 weeks)
- Continue until delivery
High-risk indications with one or more of the fiollowing:
- History of preeclampsia
- Multifetal gestation
- Chronic hypertension
- Type 1 or type 2 diabetes
- Chronic kidney disease
- Autoimmune disease (SLE, antiphospholipid syndrome)
Moderate-risk factors more than one of the following:
- First pregnancy
- Age ≥ 35
- Family history of preeclampsia
- Interpregnancy interval > 10 years
- BMI > 30 kg/m²
- Socioeconomic risk or African American race (as risk markers, not biology)
- Personal history of SGA infant or previous adverse pregnancy outcome.
- In vitro fertilization
International Recommendations
NICE (UK) recommends 75–150 mg daily from 12 weeks until delivery for individuals with high-risk or multiple moderate-risk factors. (The historical 75 mg dose corresponds to the older UK tablet strength.)
Canadian guidelines similarly support low-dose aspirin in high-risk pregnancies.
References ▼1. Duley L, et al. Antiplatelet agents for preventing pre-eclampsia and its complications. Cochrane Database Syst Rev. 2007; CD004659. PMID: 17443552
2. SOGC Clinical Practice Guideline – Hypertensive disorders of pregnancy. J Obstet Gynaecol Can. 2008.
3. American College of Chest Physicians. Antithrombotic Therapy and Prevention of Thrombosis, 9th ed. Chest. 2012;141:e691S–736S.
4. NICE Clinical Guideline 107 – Hypertension in pregnancy. 2010–2011 updates.
5. NICE guideline: Hypertensive disorders during pregnancy (updated).
Updated U.S. guidance:
ACOG Committee Opinion No. 743 (reaffirmed 2023): Low-dose aspirin use during pregnancy.
SMFM Consult Series #52 (2018).
Low-Dose Aspirin Use for the Prevention of Preeclampsia and Related Morbidity and Mortality Practice Advisory December 2021. 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 Accessed 11/29/2025