Is it safe to take aspirin (acetylsalicylic acid) during pregnancy?

Aspirin Use During Pregnancy

Regular-dose aspirin should be avoided during pregnancy, especially in the third trimester, while low-dose aspirin (81-100 mg daily) is recommended only for specific high-risk women to prevent preeclampsia. 1, 2

Safety of Aspirin in Pregnancy

Regular-Dose Aspirin

• Regular-dose aspirin is contraindicated during pregnancy, particularly during the last trimester
• The FDA label explicitly warns that aspirin use during the last 3 months of pregnancy may cause problems in the unborn child or complications during delivery 1
• Women should always consult a healthcare professional before using any aspirin during pregnancy

Low-Dose Aspirin (81-100 mg daily)

• Low-dose aspirin is considered safe and beneficial ONLY for specific high-risk populations 3, 4
• It should be initiated between 12-16 weeks gestation (optimally before 16 weeks) and continued until delivery 2, 3
• Recent evidence suggests that initiating low-dose aspirin even before 11 weeks gestation may not increase the risk of maternal, fetal, or neonatal adverse events 5

Indications for Low-Dose Aspirin in Pregnancy

High-Risk Factors (single factor sufficient for recommendation):

• History of preeclampsia, especially early-onset requiring delivery before 34 weeks
• Multifetal gestation
• Chronic hypertension
• Type 1 or type 2 diabetes
• Renal disease
• Autoimmune diseases (particularly systemic lupus erythematosus)
• History of preeclampsia 2, 3, 4

Moderate-Risk Factors (more than one factor needed for recommendation):

• First pregnancy
• Maternal age ≥35 years
• BMI >30
• Family history of preeclampsia
• Sociodemographic risk factors 3, 4

Important Contraindications

• History of aspirin allergy
• Bleeding disorders
• Active peptic ulcer disease 2

Clinical Algorithm for Aspirin Use in Pregnancy

1. Assess risk factors for preeclampsia at first prenatal visit
2. If high-risk (any single high-risk factor): Recommend low-dose aspirin (81 mg daily)
3. If moderate-risk (multiple moderate risk factors): Consider low-dose aspirin
4. If low-risk (no high-risk factors and fewer than two moderate-risk factors): Do NOT recommend aspirin
5. When to start: Between 12-16 weeks gestation (optimally before 16 weeks)
6. When to stop: Continue until delivery
7. Contraindications: Do not use if history of aspirin allergy, bleeding disorders, or active peptic ulcer disease

Important Caveats

• Low-dose aspirin has NOT been proven beneficial for prevention of early pregnancy loss, fetal growth restriction, stillbirth, or preterm birth in women without high-risk factors for preeclampsia 3, 4, 6
• The safety profile of low-dose aspirin (≤100 mg daily) differs significantly from regular-dose aspirin 6
• While recent evidence suggests early initiation (before 11 weeks) may be safe 5, most guidelines still recommend starting between 12-16 weeks gestation 2, 3
• Always consult with an obstetrician before starting any medication during pregnancy, including aspirin