Predictive value of clinical chorioamnionitis in extremely premature infants

Clinical chorioamnionitis and histological chorioamnionitis are important risk factors for neonatal complications and neurodevelopmental impairment in premature infants. It is unclear, however, whether a diagnosis of clinical chorioamnionitis is sufficient to establish a diagnosis of histological chorioamnionitis. The aim of this study was to evaluate the predictive value of clinical chorioamnionitis in the diagnosis of histological chorioamnionitis in extremely premature infants.

This study was a secondary analysis of data from the Neonatal Research Network in Japan, a population-based cohort study aimed at identifying the clinical characteristics and morbidity of very low-birthweight infants. Data for extremely premature infants <28 weeks' gestational age from 2003 to 2007, were used. Subset analysis investigated positive predictive value by gestational age.

Of the 2470 infants analyzed, 786 were diagnosed with clinical chorioamnionitis and 1129 with histological chorioamnionitis. The positive predictive value of clinical chorioamnionitis for histological chorioamnionitis was 86.6% (681/786; 95% confidence interval [CI]: 84.4-88.6%), sensitivity was 60.3% (681/1129; 95%CI: 58.8-61.7%), and specificity was 92.2% (1236/1341; 95%CI: 90.9-93.3%). In subset analysis, the positive predictive value was particularly high at 23 weeks of gestation (89.1%; 115/129), with sensitivity of 65.3% (115/176) and specificity of 89.6% (120/134).

The finding that clinical chorioamnionitis is a useful predictor of histological chorioamnionitis provides important insights into the relationship between these two diagnoses, and has important implications in determining the appropriate timing of delivery of extremely premature infants.