Placental growth factor at 24–28 weeks for aspirin discontinuation in pregnancies at high risk for preterm preeclampsia: Post hoc analysis of StopPRE trial

Introduction This study aims to evaluate the safety of discontinuing aspirin treatment at 24–28 weeks in women at high risk after first‐trimester combined screening for preeclampsia (PE) and normal placental growth factor (PlGF) levels at 24–28 weeks of gestation. Material and Methods This is a post hoc analysis of the StopPRE trial, conducted at nine Spanish maternity hospitals from September 2019 to September 2021. In the StopPRE trial, all high‐risk single pregnancies identified during first‐trimester screening for PE were treated with 150 mg of daily aspirin. Out of 1604 eligible women with a soluble fms‐like tyrosine kinase‐1 to PlGF ratio (sFlt‐1/PlGF) ≤38 at 24–28 weeks, 968 were randomly assigned in a 1:1 ratio to either continue aspirin until 36 weeks (control group) or discontinue it (intervention group). In this secondary analysis, only women with PlGF ≥100 pg/mL at 24–28 weeks were included. As in the StopPRE trial, the non‐inferiority margin was set at a 1.9% difference in preterm PE incidence between the groups. Results Among the 13 983 screened pregnant women, 1984 (14.2%) were deemed high‐risk for preterm PE, of which 397 (20.0%) were ineligible, 636 declined participation, and 32 were excluded. Ultimately, 919 women with PlGF >100 pg/mL were randomized and included in this analysis. Preterm PE occurred in 0.9% of the intervention group (4 out of 465) and 1.5% of the control group (7 out of 454), indicating non‐inferiority of aspirin discontinuation. There were no significant differences between the groups in adverse pregnancy outcomes before 37 weeks, at