A meta-analysis of low-dose aspirin for the prevention of pregnancy-induced hypertensive disease.
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.


CONCLUSIONS
--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.
Imperiale
T F
TF
Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, Ohio.
Petrulis
A S
AS
D001241:Aspirin / Q000008:administration & dosage* / Q000009:adverse effects; D002585:Cesarean Section / Q000706:statistics & numerical data; D002986:Clinical Trials as Topic; D005260:Female; D006801:Humans; D006973:Hypertension / Q000517:prevention & control*; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D015201:Meta-Analysis as Topic; D011225:Pre-Eclampsia / Q000517:prevention & control; D011247:Pregnancy; D011249:Pregnancy Complications, Cardiovascular / Q000517:prevention & control*; D011256:Pregnancy Outcome
D001241:Aspirin