The original trial of low-dose aspirin in high-risk patients indicated no effect of aspirin on outcome. In this study, the overall incidence of preeclampsia was not significantly different in the aspirin and placebo treated groups (20% versus 23%, p = 0.31). This was also true in the individual high-risk groups (p≥0.05). In addition, there was no difference in the concentrations of sFlt1, sEng and PlGF between women who were in the aspirin treatment group and those in the placebo group (p≥0.05). Formal tests for interaction between treatment group and the markers were not significant. For these reasons, aspirin treated and placebo groups were combined for these analyses.