Is it safe to take baby (acetylsalicylic acid) aspirin during pregnancy due to the risk of hemorrhaging?

Low-Dose Aspirin During Pregnancy: Hemorrhage Risk Assessment

Low-dose aspirin (81-100 mg daily) during pregnancy does NOT significantly increase the risk of maternal hemorrhage and is considered safe when appropriately indicated, though there is a small increased risk of bleeding complications at delivery that must be weighed against substantial benefits in high-risk women. 1, 2

Maternal Hemorrhage Risk: The Evidence

Postpartum Hemorrhage

• No significant increase in postpartum hemorrhage risk across 9 trials involving 22,760 women (RR 1.02,95% CI 0.96-1.09) 1
• Five trials examining blood loss found no evidence that low-dose aspirin affected the amount of bleeding at delivery 1
• However, one 2021 Swedish population study of 313,624 women found a modest increase in postpartum hemorrhage among aspirin users (10.2% vs 7.8%; adjusted OR 1.23,95% CI 1.08-1.39), with this risk primarily in vaginal deliveries but not cesarean sections 3

Placental Abruption

• No increased risk of placental abruption in pooled analysis of 11 RCTs with 23,332 women (RR 1.17,95% CI 0.93-1.48) 1, 2
• This finding contradicts earlier concerns from the 1990s that had limited aspirin recommendations 1

Antepartum Bleeding

• No association with bleeding complications during the antepartum period (adjusted OR 1.22,95% CI 0.97-1.54) 3

Fetal and Neonatal Hemorrhage Risk

Intracranial Hemorrhage in Neonates

• No increased risk in pooled analysis of 6 studies with 22,158 neonates (RR 0.84,95% CI 0.61-1.16) 1, 2
• One Swedish study reported increased neonatal intracranial hemorrhage (0.07% vs 0.01%; adjusted OR 9.66,95% CI 1.88-49.48), though absolute numbers were extremely small 3

Perinatal Mortality

• No harm demonstrated: pooled analysis of 22,848 pregnancies showed RR 0.92 (95% CI 0.76-1.11) 1, 2
• When limited to high-risk women, the estimate approached statistical significance for benefit (RR 0.81,95% CI 0.65-1.01) 1

Clinical Decision Framework

When Benefits Clearly Outweigh Risks (Recommend Aspirin)

High-risk factors (presence of any one warrants aspirin 81 mg daily starting 12-28 weeks, optimally before 16 weeks): 4, 5

• History of preeclampsia, especially early-onset (<34 weeks)
• Chronic hypertension
• Type 1 or 2 diabetes
• Renal disease
• Autoimmune disease (e.g., lupus, antiphospholipid syndrome)
• Multifetal gestation

Consider Aspirin (Multiple Moderate-Risk Factors)

Moderate-risk factors (≥2 factors warrant consideration): 4, 5

• First pregnancy
• Maternal age ≥35 years
• BMI >30
• Family history of preeclampsia
• Low socioeconomic status
• Prior adverse pregnancy outcome

When NOT to Use Aspirin

• Low-risk women without indications (no proven benefit for preventing early pregnancy loss, fetal growth restriction, stillbirth, or preterm birth in this population) 4, 5
• Aspirin desensitization therapy for aspirin-exacerbated respiratory disease must be discontinued before pregnancy due to unacceptable fetal risks 2

Important Caveats and Risk Mitigation

Timing Considerations

• Start between 12-28 weeks gestation (optimally before 16 weeks for maximum preeclampsia prevention) 4, 5
• Continue daily until delivery 4, 5
• Some sources suggest discontinuing 1-2 weeks before planned delivery to reduce bleeding risk, though this is not universally recommended 6

First Trimester Concerns

• Possible increased risk of gastroschisis with first trimester exposure (OR 2.37,95% CI 1.44-3.88), though the American College of Chest Physicians notes this estimate has "questionable validity" due to significant study bias 1, 2
• Meta-analyses of randomized trials failed to establish increased miscarriage risk (RR 0.92,95% CI 0.71-1.19) 1, 2

Long-Term Safety

• No adverse developmental effects at 18-month follow-up in the largest trial (CLASP), including gross motor development, height, weight, or hospital visits 1, 2
• No increased cryptorchidism in male infants exposed in utero 1, 2

The Bottom Line on Hemorrhage Risk

The U.S. Preventive Services Task Force concluded with "moderate certainty that the magnitude of net benefit is substantial" for high-risk women, finding that harms of low-dose aspirin use in pregnancy are "no greater than small." 1, 2 The modest increase in postpartum bleeding observed in one large observational study 3 is outweighed by the proven reductions in preeclampsia, preterm birth, and intrauterine growth restriction in appropriately selected high-risk patients. 1, 2

The FDA label cautions against aspirin use in the last 3 months of pregnancy unless directed by a physician 7, but this reflects concerns about high-dose aspirin rather than the low-dose prophylactic regimen supported by current obstetric guidelines.