A randomised trial of low dose aspirin for primiparae in pregnancy

Objective To investigate whether low dose aspirin medication given to primiparous women provides benefit in preventing pre-eclampsia or intrauterine growth retardation.
Design Randomised double-blind controlled trial of low dose aspirin and placebo in pregnancy.
Population Residents of the parishes of Kingston and St Andrew, Jamaica; 6275 primiparae enrolled between 12 and 32 weeks of gestation.
Main outcome measures Hypertensive disorders of pregnancy (including pre-eclampsia and eclampsia), preterm delivery, and low birthweight. In addition, to assess whether enrolment early, rather than late had more beneficial effect. Possible adverse effects on the woman and her infant were monitored.
Results Of enrolled primiparae, 97% were followed throughout pregnancy. There were no differences between those on aspirin and those on placebo in the development of hypertensive disorders (e.g. for a rise in diastolic pressure of 25 mmHg the odds ratio [OR] was 1.02 [95% CI 0.86–1.211; for proteinuric pre-eclampsia OR 1.15 [95% CI 0.92–1.44]; eclampsia OR 0.82 [95% CI 0.44–1.531); except for oedema which was significantly less prevalent in those on aspirin (OR 0.85 [95% CI 0.75–0.961). Women on aspirin were not significantly less likely to deliver preterm (OR 0.93 [95% CI 0–79-1.091) or have a larger fetus (mean birthweight difference 18 g [95% CI -9 to 451). They were, however, significantly more likely to suffer from bleeding disorders antenatally, intrapartum and postpartum; for postpartum haemorrhage OR 1.40 (95% CI 1.13–1-73).
Conclusions This trial shows that low dose aspirin has no consistent beneficial effect in primiparae.