Elevated neutrophil-lymphocyte ratios in extremely preterm neonates with histologic chorioamnionitis.

Histologic chorioamnionitis (HCA) is a placental inflammation linked to preterm birth and adverse neonatal outcome. The neutrophil-lymphocyte ratio (NLR) can identify various inflammatory disorders, however its utility in HCA is not clear. Our goal was to examine NLR values and HCA diagnoses in at-risk pregnancies and neonates. We retrospectively analyzed the EHR of mothers and preterm (<33 wk GA) neonates with or without HCA (identified by placental histology). The NLR was calculated from complete blood counts in laboring women and in their neonates (0–24 h of life). In 712 consecutive gestations, 50.8% had HCA (26.5% fetal HCA). The neonatal NLR (0–12 h, 13–24 h) predicted fetal HCA better than chance alone (p = 0.01 and 0.002, respectively). Early NLR elevation in preterm neonates is consistent with a diagnosis of fetal HCA. The NLR may identify preterm neonates at risk for HCA-related complications.