358: Relationship between 1st trimester fetal fraction of cell-free DNA from maternal plasma and preeclampsia in a large general pregnancy population

We analyzed the Non-invasive Examination of Trisomy (NEXT) Study database to investigate whether the fetal cell-free DNA (cfDNA) fraction in maternal plasma at 10-4 weeks of gestation is different in pregnancies in which preeclampsia subsequently develops from pregnancies without this complication. A secondary analysis of the NEXT database, which prospectively enrolled 18,955 subjects to compare the performance of first trimester combined screening to cfDNA analysis (Harmony Prenatal Test), was performed. The analysis population included 15,715 subjects with live births and known pregnancy outcomes. Fetal fraction (FF) were compared between patients with either preeclampsia (PE) or ‘no pre-eclampsia’ (NP). FF was corrected for maternal weight and gestational age at blood draw. The incidence of PE among patients with live born pregnancies was 3.2%. The mean percentage of fetal cfDNA was 11.04 % in NP patients compared to 10.06 % in PE patients (p< 0.0001). There was no difference in the FF in patients with PE delivering at <34 weeks (53 patients) compared to the entire group of PE patients (504). At a single measurement of FF during the 1st trimester, there is a statistically significant reduction in FF in patients destined to develop PE versus those that do not develop this complication. Additional studies are warranted to determine if FF may be used as one among a panel of biomarkers and biometrics for the prediction of preeclampsia.