Aspirin Reduces Risk for Preeclampsia, but Who Should Be Treated?

A meta-analysis found a significant decrease in the rate of preeclampsia, but the benefits of treatment are small and the risks unclear.

The poorly understood etiology of preeclampsia seems to involve inflammation, placental damage, prostaglandin imbalance, and activation of platelets and the clotting system. Some early trials suggested that antiplatelet agents might prevent or delay preeclampsia, but subsequent larger studies suggested that the benefits were modest at best. Investigators have now combined unpublished individual patient data from 31 primary-prevention trials in which more than 32,000 pregnant women at risk for preeclampsia were randomized to receive one or more antiplatelet agents (primarily aspirin), a placebo, or no treatment.

Antiplatelet agents were associated with a 9% to 10% reduction in relative risk for each of four major outcomes (preeclampsia, delivery before 34 weeks’ gestation, stillbirth or infant death before hospital discharge, and small infant for gestational age) and a composite outcome including all of the above plus maternal death. Only the reductions in preeclampsia, preterm delivery, and the composite outcome were statistically significant. The groups did not differ significantly in any other maternal outcomes, including potential adverse effects of antiplatelet therapy (e.g., perinatal hemorrhage). Need for assisted ventilation was a significant 21% lower among infants whose mothers received antiplatelet agents. Outcomes did not differ significantly by dose of aspirin or timing of treatment, or in any prespecified subgroup of women.

Comment: This meta-analysis was strengthened by returning to individual patient data and standardizing outcome definitions. But the potential long-term risks of antiplatelet therapy remain unclear, and even this large study was unable to identify a high-risk subgroup in which the benefit of treatment is substantial. Editorialists suggest that risks and benefits be weighed for each individual patient.

— Bruce Soloway, MD

Published in Journal Watch General Medicine June 26, 2007

Citation(s):
Askie LM et al. Antiplatelet agents for prevention of pre-eclampsia: A meta-analysis of individual patient data. Lancet 2007 May 26; 369:1791-8.
[Medline abstract] (Free)
Roberts JM and Catov JM. Aspirin for pre-eclampsia: Compelling data on benefit and risk. Lancet 2007 May 26; 369:1765-6.