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

Abstract 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.