820: Elevated plasma S100 protein levels in preterm gestations with histologic chorioamnionitis

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Histologic chorioamnionitis (HCA) is an inflammatory process that may be clinically silent and linked with preterm birth. S100 proteins are inflammatory markers which have been identified in amniotic fluid of mothers affected by HCA. We explored the relationship of S100A8 and S100A12 levels in mother-baby pairs with HCA compared to unexposed controls. We hypothesized that S100 protein expression levels are increased in mother-baby pairs affected by HCA. This is a prospective observational cohort of singleton or uncomplicated twin gestations from 230/7 to 346/7 weeks with preterm labor or preterm premature rupture of membranes (PPROM). Exclusion criteria included any maternal inflammatory disorder. Maternal peripheral blood was obtained within 24 h peripartum and venous umbilical cord blood samples were obtained at delivery. Diagnoses of maternal (M-HCA) or fetal (F-HCA) or the absence of HCA (Ctrl) were determined by placental examination per Redline HCA definitions (Redline 2012). S100A8 and S100A12 levels were measured by commercial ELISA. Data were analyzed using appropriate statistical methods. S100 protein levels were determined in plasma samples from 41 mother-baby pairs (7 M-HCA, 22 F-HCA, 12 Ctrl). Demographic data, PPROM incidence and gestational age at delivery were similar between groups. In F-HCA, S100A8 levels were increased 2-fold in maternal blood (p< .05) and 4-fold in cord blood (p< .001) relative to Ctrl. In F-HCA, maternal and cord blood S100A8 levels were similar, but in M-HCA, maternal levels were higher (p=.01). Cord blood S100A12 levels were 4-fold higher with F-HCA vs. Ctrl (p< .0001). In contrast, maternal S100A12 levels were similar across conditions. Fetal HCA is associated with elevated S100A8 and S100A12 levels in maternal and neonatal plasma. Our data suggest that maternal S100A8 blood levels may uniquely identify fetal HCA, a diagnosis that currently depends on postpartum placental analysis. Studies to establish the utility of S100A8 as a biomarker of HCA in a more extensive population are planned.