Background: Chorioamnionitis is a recognized risk factor of preterm delivery; however, controversy still persists concerning the relationship between maternal inflammation and neonatal morbidity and mortality. Objective: To determine the incidence of clinical chorioamnionitis and its relationship to morbidity and mortality among very-low-birth-weight (VLBW) infants. Methods: This was a retrospective analysis of prospectively collected data of VLBW neonates ≤32 weeks' gestational age (GA) admitted to collaborating units in the Spanish SEN1500 Network between January 2008 and December 2011. Clinical chorioamnionitis was defined by obstetricians based on clinical findings, and neonatal outcomes were compared between exposed and non-exposed infants by multivariate logistic regression analysis. Results: During the study period, 11,464 VLBW newborns were admitted to our units and 10,026 were ≤32 weeks' GA. Among them, 8,330 (83.1%) had complete data and were included. Of these, 1,480 (17.8%) were exposed to maternal clinical chorioamnionitis. The incidence was higher at lower GA and, after adjusting for confounding factors, exposed infants had higher risks of early-onset neonatal sepsis (EONS) (10.0 vs. 2.8%; aOR 3.102; 95% CI 2.306-4.173; p < 0.001) and necrotizing enterocolitis (NEC) (11.2 vs. 7.7%; aOR 1.300; 95% CI 1.021-1.655; p < 0.033), but lower risks of patent ductus arteriosus (PDA) (43.2 vs. 34.9%; aOR 0.831; 95% CI 0.711-0.971; p < 0.02) and late-onset bacterial sepsis (LONS) (36.6 vs. 32.5%; aOR 0.849; 95% CI 0.729-0.989; p < 0.035). There were no differences in mortality between the groups. Conclusions: The incidence of maternal clinical chorioamnionitis is inversely related to GA at delivery, and in VLBW infants ≤32 weeks' GA it is associated with higher risks of EONS and NEC, but lower risks of PDA and LONS. We did not found differences in survival.

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