Use of low-dose aspirin lowers the risk for preeclampsia among women determined to be at high risk during first-trimester screening, according to a study presented at a meeting of the Fetal Medicine Foundation and published in the New England Journal of Medicine.

Over 1,700 high-risk women with singleton pregnancies were randomised to receive 150-mg aspirin or placebo daily from 11–14 weeks' gestation until 36 weeks. Women were determined to be at high risk (>1 in 100) based on an algorithm that incorporated maternal factors (e.g., age, obstetric history) and biomarkers (e.g., mean arterial pressure, uterine-artery pulsatility index). A tenth of participants had a prior pregnancy with preeclampsia.

The primary outcome — delivery with preeclampsia before 37 weeks' gestation — occurred in 1.6% of the aspirin group versus 4.3% of the placebo group. Aspirin's benefits were seen regardless of obstetric history or magnitude of risk at screening. Adverse events did not differ between the groups.