Mid-trimester uterine artery Doppler for aspirin discontinuation in pregnancies at high risk for preterm pre-eclampsia : Post-hoc analysis of StopPRE trial

Objective: To assess whether aspirin treatment can be discontinued in pregnancies with normal uterine artery pulsatility index (≤90th percentile) at 24-28 weeks. Design: Post-hoc analysis of a clinical trial. Setting: Nine maternity hospitals in Spain. Population or Sample: Pregnant individuals at high risk of pre-eclampsia at 11-13 weeks and normal uterine artery Doppler at 24-28 weeks. Methods: All participants received treatment with daily aspirin at a dose of 150 mg. Participants were randomly assigned, in a 1:1 ratio, either to continue aspirin treatment until 36 weeks (control group) or to discontinue aspirin treatment (intervention group), between September 2019 and September 2021. In this secondary analysis, women with a UtAPI >90th percentile at 24-28 weeks were excluded. The non-inferiority margin was set at a difference of 1.9% for the incidence of preterm pre-eclampsia. Main outcome measures: Incidence of preterm pre-eclampsia. Results: Of the 1611 eligible women, 139 were excluded for UtAPI >90th percentile or if UtAPI was not available. Finally, 804 were included in this post-hoc analysis. Preterm pre-eclampsia occurred in three of 409 (0.7%) women in the aspirin discontinuation group and five of 395 (1.3%) women in the continuation group (−0.53; 95% CI −1.91 to 0.85), indicating non-inferiority of aspirin discontinuation. Conclusions: Discontinuing aspirin treatment at 24-28 weeks in women with a UtAPI ≤90th percentile was non-inferior to continuing aspirin treatment until 36 weeks for preventing preterm pre-eclampsia.