Can pregnant women take aspirin (acetylsalicylic acid)?

Aspirin Use During Pregnancy

Low-dose aspirin (81-150 mg daily) is recommended for pregnant women at high risk of preeclampsia, starting at 12-16 weeks of gestation and continuing until delivery, but should generally be avoided during the last trimester unless specifically indicated for preeclampsia prevention. 1, 2

Indications for Low-Dose Aspirin in Pregnancy

High-Risk Conditions (Aspirin Recommended)

• History of preeclampsia
• Multifetal gestation
• Chronic hypertension
• Type 1 or type 2 diabetes
• Renal disease
• Autoimmune diseases (especially SLE and APS)
• Multiple moderate risk factors

Moderate Risk Factors (Consider Aspirin if ≥2 Present)

• First pregnancy
• Maternal age ≥35 years
• BMI >30 kg/m²
• Family history of preeclampsia
• Sociodemographic risk factors 1, 3

Dosing and Timing

• Dose:
  • 81-100 mg daily (US guidelines) 1, 3
  • 150 mg daily (European guidelines) 4
• Timing: Start between 12-16 weeks of gestation (optimally before 16 weeks) 5, 1
• Duration: Continue until delivery 1

Special Populations

Systemic Lupus Erythematosus (SLE)

• All SLE patients should receive low-dose aspirin (81-100 mg daily) starting in the first trimester 5
• Should be combined with hydroxychloroquine if possible 5

Antiphospholipid Syndrome (APS)

• For obstetric APS: Combine low-dose aspirin with prophylactic-dose heparin/LMWH 5
• For thrombotic APS: Combine low-dose aspirin with therapeutic-dose heparin/LMWH 5
• Continue prophylactic anticoagulation for 6-12 weeks postpartum 5

Diabetes (Type 1 or 2)

• Low-dose aspirin (100-150 mg/day) recommended starting at 12-16 weeks 5
• In the US, 81 mg tablets are commonly available (two tablets may be used) 5

Safety Considerations

Contraindications and Cautions

• FDA notes that aspirin should generally be avoided during the last 3 months of pregnancy unless specifically directed by a doctor 2
• Low-dose aspirin (≤100 mg daily) is considered safe during pregnancy with minimal risk of serious maternal or fetal complications 6, 3
• Decision regarding discontinuation prior to delivery should be made by the obstetrician and anesthesiologist based on the patient's specific situation 5

Ineffective Uses

• Low-dose aspirin is NOT recommended for:
  • Prevention of early pregnancy loss in the absence of high-risk factors
  • Prevention of fetal growth restriction without other risk factors
  • Prevention of stillbirth or preterm birth without other risk factors 3, 7

Monitoring

• Regular blood pressure monitoring
• Assessment of proteinuria
• Fetal growth monitoring
• Monitoring for any bleeding complications

Key Pitfalls to Avoid

1. Starting too late: Aspirin should be initiated before 16 weeks for optimal effectiveness 8, 4
2. Inadequate dosing: Some evidence suggests doses >100 mg may be more effective 4
3. Stopping prematurely: Continue until delivery unless complications arise
4. Missing high-risk patients: Systematically screen all pregnant women for preeclampsia risk factors
5. Using for unproven indications: Not effective for preventing pregnancy loss, fetal growth restriction, or preterm birth in low-risk women

Remember that while aspirin is generally contraindicated in the third trimester of pregnancy according to FDA labeling, the specific exception for preeclampsia prevention is supported by multiple guidelines and should be continued until delivery in high-risk women.