Effects of aspirin consumption during pregnancy on pregnancy outcomes: meta-analysis.

Background: We assessed the effects and safety of aspirin treatment during pregnancy on fetal and neonatal outcomes.

Methods: We searched MEDLINE (1966-2001), EMBASE (1980-2000), TOXLINE (1994-2000), EB M Cochrane Database of Systematic Reviews (1991-2000), Reproductive Toxicology (2001), teratology texts, and bibliographies of all the included studies. We looked for published randomized controlled studies reporting aspirin treatment to improve outcomes of moderate- and high-risk pregnancies. The key words used to search for articles about exposure to aspirin were salicylic acid, pregnancy, and pregnancy complications; key words used to search for outcome were neonatal diseases and abnormalities. Based on our search strategy, 1904 citations were identified; their titles and abstracts were reviewed by one reviewer. Of these citations, 182 papers were selected for detailed review. Two reviewers independently determined whether a study should be included in the final analysis. In cases of disagreement, the decision was based on the assessment of a third reviewer.

Results: Data were extracted independently by each reviewer. We calculated the pooled relative risk (RR) or weighted mean difference and 95% confidence intervals (CI), assuming a random-effect model. Thirty-eight studies met the inclusion criteria. The risk for miscarriage did not differ between women treated with aspirin andplacebo (seven studies; RR, 0.92; 95% CI, 0.71-119). Women who took aspirin had a significantly lower risk of preterm delivery than did those treated with placebo (22 studies; RR, 0.92; 95% CI, 0.86-0.98). There was no significant difference in perinatal mortality (20 studies; RR, 0.92; 95% CI, 0.81-1.05) and in the rate of small-for-gestational-age infants (12 studies; RR, 0.96; 95% CI, 0.87-1.07) among offspring of mothers treated with aspirin and those of mothers treated with a placebo.

Conclusion: For women with moderate- and high-risk pregnancies, aspirin treatment seemed to have a small but significant effect on reducing the rate of preterm deliveries, but did not reduce the rate of perinatal death.