• Acetylsalicylic acid;
  • aspirin;
  • Doppler;
  • intrauterine growth restriction;
  • meta-analysis;
  • pre-eclampsia;
  • pregnancy;
  • prevention;
  • uterine artery

Objective  To study the effect of aspirin in the prevention of pre-eclampsia in high-risk women.

Design  Randomised, double-blinded, placebo-controlled trial.

Setting  Maternity clinics in ten Finnish hospitals participating in the PREDO Project.

Sample  A total of 152 women with risk factors for pre-eclampsia and abnormal uterine artery Doppler velocimetry.

Methods  Participants were randomised to start either aspirin 100 mg/day or placebo at 12 + 0 to 13 + 6 weeks + days of gestation. Because of the limited power of this trial, we also conducted a meta-analysis of randomised controlled trials that included data on 346 women with abnormal uterine artery Doppler flow velocimetry, and aspirin 50–150 mg/day started at or before 16 weeks of gestation.

Main outcome measure  Pre-eclampsia, gestational hypertension and birthweight standard deviation (SD) score. Outcome measures for the meta-analysis were pre-eclampsia, severe pre-eclampsia, preterm (diagnosed <37 + 0 weeks of gestation) and term pre-eclampsia.

Results  From the 152 randomised women, 121 were included in the final analysis. Low-dose aspirin did not reduce the rate of pre-eclampsia (relative risk [RR] 0.7, 95% CI 0.3–1.7); gestational hypertension (RR 1.6, 95% CI 0.6–4.2); early-onset pre-eclampsia (diagnosed <34 + 0 weeks of gestation) (RR 0.2, 95% CI 0.03–2.1); or severe pre-eclampsia (RR 0.4, 95% CI 0.1–1.3); and the results were not statistically significant in an intention-to-treat analysis. However, our meta-analysis, including the current data, suggested that low-dose aspirin initiated before 16 weeks of gestation reduces the risk of pre-eclampsia (RR 0.6, 95% CI 0.4–0.8) and severe pre-eclampsia (RR 0.3, 95% CI 0.1–0.7).

Conclusions  Our trial showed no statistically significant effect of aspirin in preventing pre-eclampsia in high-risk women. However, our meta-analysis suggested that aspirin may reduce the incidence of pre-eclampsia.