Abstract-Preeclampsia is a pregnancy-specific syndrome that causes substantial maternal and fetal morbidity and mortality. The etiology is incompletely understood, and there is no clinically useful screening test. Current metabolomic technologies have allowed the establishment of metabolic signatures of preeclampsia in early pregnancy. Here, a 2-phase discovery/validation metabolic profiling study was performed. In the discovery phase, a nested case-control study was designed, using samples obtained at 15Ϯ1 weeks' gestation from 60 women who subsequently developed preeclampsia and 60 controls taking part in the prospective Screening for Pregnancy Endpoints cohort study. Controls were proportionally population matched for age, ethnicity, and body mass index at booking. Plasma samples were analyzed using ultra performance liquid chromatography-mass spectrometry. A multivariate predictive model combining 14 metabolites gave an odds ratio for developing preeclampsia of 36 (95% CI: 12 to 108), with an area under the receiver operator characteristic curve of 0.94. These findings were then validated using an independent case-control study on plasma obtained at 15Ϯ1 weeks from 39 women who subsequently developed preeclampsia and 40 similarly matched controls from a participating center in a different country. The same 14 metabolites produced an odds ratio of 23 (95% CI: 7 to 73) with an area under receiver operator characteristic curve of 0.92. The finding of a consistent discriminatory metabolite signature in early pregnancy plasma preceding the onset of preeclampsia offers insight into disease pathogenesis and offers the tantalizing promise of a robust presymptomatic screening test. Key Words: preeclampsia Ⅲ metabolomics Ⅲ biomarkers Ⅲ screening Ⅲ hypertension P reeclampsia (PE) affects 5% of nulliparous pregnancies and globally afflicts Ϸ4 million women annually. It remains a leading cause of maternal death throughout the world and is responsible for significant baby morbidity and mortality. 1 Furthermore, PE has healthcare implications for the women later in life with an increased risk of hypertension, coronary artery disease, stroke, and type 2 diabetes mellitus. 2 Although the precise etiology of the disease is unclear, accumulating evidence suggests that the disease results from complex interaction between a poorly perfused placenta, because of defective remodeling of the uteroplacental arteries in early pregnancy, and a maternal response to placentalderived triggers, which results in widespread vascular endothelial cell dysfunction. 1,3,4 Widespread plasma alterations precede the clinical onset of PE, and there is intense interest in the identification of predictive biomarkers. 5 Numerous candidate biomarkers have been proposed for prediction of disease, including placental hormones, angiogenic factors, and lipids. 3,6 -8 To date, none (nor any combination) has emerged with the requisite specificity and sensitivity to be of clinical use. 5 Consequently, clinicians are unable to offer either targeted surveil...