This study aimed to optimize the strategy of aspirin to prevent preeclampsia, by exploring whether aspirin discontinuation at 28 weeks of gestation to prevent preterm PE is not inferior to 36 weeks of gestation. We will include pregnant women with normal NT scan who meet at least one high-risk factor or at least two medium-risk factors. During 12-16 weeks of gestation, the mean arterial pressure (MAP) and placental growth factor (PlGF) are measured, then initiating aspirin 100mg qn. At 24-27+6 weeks of gestation, the patients were 1:1 randomly divided into two groups, sFlt-1 and PlGF were detected at the same time. The experimental group discontinue aspirin at 28 weeks of gestation, and the control group receive aspirin until 36 weeks of gestation. The incidence of preterm PE in the two groups was compared by non-inferiority test, and the non-inferiority threshold was 2%.
