Association between placental histological chorioamnionitis and respiratory distress syndrome in preterm infants: a retrospective cohort study.

OBJECTIVE: To evaluate the independent association between placental histological chorioamnionitis (HCA) and respiratory distress syndrome (RDS) in preterm infants and explore whether this association varied by gestational age and histological stage. The incremental predictive value of HCA beyond gestational age and birth weight was also assessed. METHODS: This single-center retrospective cohort study included 689 preterm infants born at <34 weeks of gestation between June 2020 and June 2025 with definitive placental histopathological findings; 392 were HCA-negative and 297 were HCA-positive. Multivariable logistic regression assessed the association between HCA and RDS after adjustment for gestational age, birth weight, premature rupture of membranes, antenatal corticosteroid exposure, and maternal C-reactive protein. An HCA × gestational-age-group interaction was tested. Three exploratory models were compared: HCA alone, gestational age plus birth weight, and gestational age plus birth weight plus HCA. Model performance was evaluated using AUC, DeLong and likelihood-ratio tests, reclassification indices, calibration, and 1,000 bootstrap resamples. RESULTS: Overall, 271 infants (39.33%) developed RDS. RDS incidence was lower in the HCA-positive group than in the HCA-negative group (31.99% vs. 44.90%, P < 0.001). The incidences of RDS in stage I, II, and III HCA were 26.32%, 30.61%, and 55.56%, respectively (P = 0.004). Among infants born at <32 weeks, RDS incidence was lower in the HCA-positive group (33.81% vs. 52.94%, P = 0.001), whereas no significant difference was observed at 32-<34 weeks (30.38% vs. 38.74%, P = 0.093). After adjustment, HCA remained associated with lower odds of RDS (adjusted OR = 0.654, 95% CI: 0.472-0.906, P = 0.011), but the interaction with gestational-age group was not significant (P = 0.184). HCA alone showed poor discrimination (AUC=0.566). Adding HCA to gestational age and birth weight increased the AUC from 0.824 to 0.829, but the difference was not significant (P = 0.218). Bootstrap-corrected AUCs were 0.821 and 0.825. CONCLUSION: Placental HCA was independently associated with lower odds of RDS, but this observational association does not establish a causal protective effect. Gestational-age- and stage-specific findings were exploratory. HCA alone had poor discrimination, and its incremental predictive contribution beyond gestational age and birth weight was modest.