BACKGROUND AND PURPOSE:

• In the EAGeR Trial (Effects of Aspirin on Gestation and Reproduction), preconception-initiated low-dose aspirin therapy did not decrease the risk of pregnancy loss
  • ‘Intention-to-treat’ results could be impacted by nonadherence
• Naimi et al. (Annals of Internal Medicine, 2021) re-analyzed EAGeR data, estimating per protocol effects of preconception-initiated low-dose aspirin on pregnancy loss and live birth

METHODS:

• Prospective cohort study based on EAGeR trial
• Participants
  • Women aged 18 to 40 attempting pregnancy
• 1 or 2 previous pregnancy losses
• Intervention
  • Low-dose aspirin: 81 mg
  • Placebo
• Study design
  • Adherence to intervention was assessed by measuring pill bottle weights at regular intervals during follow-up
  • Outcomes were determined using pregnancy tests and medical records
• Primary outcome: Live birth
• Secondary outcomes
  • hCG-detected pregnancies
  • Pregnancy losses

RESULTS:

• 1227 women
  • Aspirin group: 615
  • Placebo: 613
• Compared to placebo, adherence to low-dose aspirin over the entire follow-up period was associated with
  • Increased hCG-detected pregnancies: Relative risk (RR) 1.12 (95% CI, 1.02 to 1.23)
  • Fewer pregnancy losses: RR 0.69 (95% CI, 0.50 to 0.95)
  • Increased live births: RR 1.33 (95% CI, 1.08 to 1.64)
• Delayed postconception initiation of low-dose aspirin therapy led to a reduction in the estimated effects especially for pregnancy loss
  • 6 weeks after conception: RR 0.70 (95% CI, 0.47 to 1.04)
  • 10 weeks after conception: RR 0.93 (95% CI, 0.65 to 1.33)
• Live birth: Effects were greater if treatment initiated before conception and continued throughout pregnancy vs starting aspirin >6 weeks
• Effects were obtained if participants adhered at a minimum of 4 days per week

CONCLUSION:

• In this study based on the EAGeR RCT, women with 1 to 2 previous losses who were adherent in their use of low dose aspirin for at least 4 days per week had an increase in live births greater than 30% vs placebo in subsequent pregnancy
• In addition, the authors conclude

Our study is the first to our knowledge to shed light on the optimal timing of LDA therapy, suggesting maximum benefits by initiating treatment before and early in pregnancy

Learn More – Primary Sources:

The Effect of Preconception-Initiated Low-Dose Aspirin on Human Chorionic Gonadotropin–Detected Pregnancy, Pregnancy Loss, and Live Birth

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