Screening for Preeclampsia in Norway With Aspirin Discontinuation at 24-28 Weeks

Study population Around 3500 pregnant women attending a routine ultrasound scan at 11-14 weeks at St. Olavs hospital, Trondheim, Norway. Study period Dec 2023 - Jul 2025 Screening Patient history, blood pressure, uterine artery mean PI and PlGF will be plotted in the FMF algorithm for screening for preeclampsia in the first trimester. Standardized blood pressure will be measured by trained personnel. Ultrasound scans will be performed by FMF certified doctors and midwives working at the Center for Fetal Medicine in Trondheim. Placenta growth factor (PLGF) will be analyzed with Kryptor technology at Center for Laboratory Medicine, St. Olavs hospital. Prophylaxis Women with high risk for preterm preeclampsia (risk \> 1:100) will be offered aspirin prophylaxis 150 mg x 1 from 11-14 weeks to 36 weeks. Women will be offered to participate in a randomized controlled trial (RCT). Study design and participants in the RCT A single center, open label, randomized, noninferiority trial conducted at St. Olavs hospital, Trondheim Norway from Dec 2023 to Jul 2025. The investigators will include around 300 women 18 years or older with a singleton live fetus, gestational age between 24 and 28 weeks, high risk of preterm preeclampsia (\>1/100) in the first trimester screening, aspirin treatment with a dose 150 mg per day initiated at 16+6 weeks of gestation or less until randomization with a adherence of at least 50% and low SFlt-1/PlGF ratio (Kryptor technology with cut-off 66). Randomization and masking Between 24 and 28 weeks of gestation, participants will be randomly designed, with a computer-based system in a 1:1 ratio, to continue aspirin (control group) or discontinue aspirin (intervention group). This is an open-label study without masking of patients or providers. Follow-up Both groups will have visits every 4 weeks between randomization and 36 weeks, and standard antenatal care after 37 weeks until delivery. Treatment adherence will be assessed by patient self-report and tablet count, and fetal growth and Doppler will be assessed at the scheduled visits between randomization and 36 weeks (at 24, 28, 32 and 36 weeks), and according to clinical judgement by obstetricians at the outpatient clinic of the hospital. Women will have a telephone/video link follow-up 1-2 months after birth