Poon LC, et al. – This article was written with the objective to investigate whether there are differences in the impact of aspirin on the incidence of preterm– preeclampsia (PE) in the ASPRE trial in subgroups characterized by maternal characteristics and medical and obstetrical history. The beneficial impact of aspirin in the prevention of preterm preeclampsia may not apply in pregnancies with chronic hypertension. There was no proof of heterogeneity in the aspirin impact in subgroups characterized by maternal characteristics and obstetrical history.