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

Aspirin Use During Pregnancy

Low-dose aspirin (81-150 mg daily) is safe and recommended during pregnancy only for women at high risk of preeclampsia, starting at 12-16 weeks gestation and continuing until delivery, but regular-dose aspirin should be avoided, especially in the third trimester. 1, 2

Indications for Low-Dose Aspirin

Low-dose aspirin is specifically indicated for women with:

High-Risk Factors:

• Type 1 or type 2 diabetes 3, 1
• History of preeclampsia 1, 4
• Chronic hypertension 1, 4
• Autoimmune diseases 1, 4
• Renal disease 1, 4
• Multifetal gestation 1, 4

Moderate Risk Factors (when multiple factors present):

• First pregnancy 1, 4
• Age ≥35 years 1, 4
• BMI >30 kg/m² 1, 4
• Family history of preeclampsia 1, 4

Dosage and Timing

• For women with diabetes: 100-150 mg daily (in the US, 81 mg tablets are commonly available) 3, 1
• For other high-risk women: 81-100 mg daily 1, 4
• Start between 12-16 weeks gestation (optimally before 16 weeks) 1, 4
• Continue daily until delivery 1, 4

Safety Considerations and Contraindications

• Low-dose aspirin during pregnancy is generally considered safe when used appropriately 4, 5
• Regular-dose aspirin should be avoided during pregnancy, especially in the third trimester, due to potential complications during delivery 2, 1
• Contraindications include:
  • History of aspirin allergy 1
  • Bleeding disorders 1
  • Active peptic ulcer disease 1

Risks and Complications

Recent evidence shows increased risks with aspirin use during pregnancy:

• Higher incidence of intrapartum bleeding (2.9% vs 1.5% in non-users) 6
• Increased postpartum hemorrhage (10.2% vs 7.8%) 6
• Higher risk of postpartum hematoma (0.4% vs 0.1%) 6
• Potential increased risk of neonatal intracranial hemorrhage 6

Important Clinical Considerations

• Low-dose aspirin should be discontinued prior to delivery based on the obstetrician and anesthesiologist's assessment 1
• The FDA warns that aspirin use during the last 3 months of pregnancy may cause problems in the unborn child or complications during delivery 2
• In the absence of high-risk factors for preeclampsia, evidence does not support using low-dose aspirin for prevention of early pregnancy loss, fetal growth restriction, stillbirth, or preterm birth 4, 5

Common Pitfalls to Avoid

• Starting aspirin too late (after 16 weeks) may reduce effectiveness 1
• Using regular-dose aspirin instead of low-dose formulations 1, 2
• Continuing regular-dose aspirin into the third trimester 2
• Prescribing aspirin for all pregnant women without risk stratification 1, 7
• Failing to consider the increased bleeding risks, particularly with vaginal deliveries 6