Low-dose aspirin initiated in early pregnancy is an efficient method of reducing the incidence of preeclampsia and IUGR.

Objective: To compare the effect of early administration of aspirin on the risk of preterm and term preeclampsia. Method: A systematic review and meta-analysis of randomized controlled trials were performed. Women who were randomized to low-dose aspirin or placebo/no treatment at or before 16 weeks of gestation were included. The outcomes of interest were preterm preeclampsia (delivery <37 weeks) and term preeclampsia. Pooled relative risks (RR) with their 95% confidence intervals (CI) were computed. Results: The search identified 7,941 citations but only five trials on a combined total of 556 women fulfilled the inclusion criteria. When compared to controls, aspirin initiated ≤16 weeks of gestation was associated with a major reduction of the risk of preterm preeclampsia (RR 0.11, 95% CI 0.04–0.33) but had no significant effect on term preeclampsia (RR 0.98, 95% CI 0.42–2.33). Conclusion: Low-dose aspirin administrated at or before 16 weeks of gestation reduces the risk of preterm but not term preeclampsia.