Background: --Pregnancy-induced hypertension (PIH), defined as either isolated hypertension after the 20th week of gestation or hypertension with proteinuria (preeclampsia), occurs in 5% to 15% of pregnancies and is associated with maternal and neonatal morbidity. Previous clinical trials with small numbers of patients have suggested that aspirin in doses of 60 to 150 mg/d during the second and third trimesters reduces the risk of PIH and improves maternal and neonatal outcomes.
Objective: --We performed a meta-analysis of the six published controlled trials to estimate more precisely (1) the magnitude of protection of aspirin from PIH; (2) the effect of aspirin on severe low-birth-weight infants, cesarean section, and perinatal mortality; and (3) the risk of adverse effects.
Methods: --We critically and independently evaluated study methods, assigned a quality score to each trial, and abstracted quantitative outcomes data. For each outcome, both relative risk (RR) and the number needed to be treated were calculated.
Results: --Among 394 subjects from six trials, the RR of PIH among women who took aspirin was 0.35 (95% confidence interval [CI], 0.22 to 0.55) and the number needed to be treated was 4.4, meaning that between four and five high-risk women would need to be treated with aspirin to prevent one case of PIH. Aspirin reduced the risk of severe low birth weight among newborns by 44% (RR = 0.56; 95% CI, 0.36 to 0.88) and reduced the risk of cesarean section by 66% overall (RR = 0.34; 95% CI, 0.25 to 0.48), although the specific indications for cesarean section were generally not described. There was no effect on fetal and neonatal death (RR = 0.88; 95% CI, 0.32 to 2.46), and there were no maternal or neonatal adverse effects associated with taking aspirin.
Conclusion: --This meta-analysis suggests that low-dose aspirin reduces the risks of PIH and severe low birth weight, with no observed risk of maternal or neonatal adverse effects.