Association of histological chorioamnionitis and fetal inflammatory response with pathogen distribution in neonatal umbilical cord blood cultures

Objective To investigate the association between different severity grades of histological chorioamnionitis (HCA), concurrent fetal inflammatory response (FIR), and pathogen distribution profiles in umbilical cord blood culture (UCBC), and to provide clinical evidence for early clinical intrauterine infection. Methods A retrospective 1:2 propensity score-matched case-control study was conducted. We systematically retrieved archived inpatient electronic medical records, placental pathological slides, and historical UCBC test data of neonates delivered at Women’s Hospital, School of Medicine, Zhejiang University between January 2021 and December 2024. All placental sections were re-reviewed by two senior pathologists in a double-blind manner according to the 2016 Amsterdam Placenta Workshop criteria. Subjects were screened strictly based on predefined inclusion and exclusion criteria. Neonates with positive UCBC results were assigned to the case group ( n = 81), while UCBC-negative neonates without clinical intrauterine infection manifestations served as matched controls ( n = 162). Matching confounders included gestational age (± 7 days), birth weight (± 250 g), delivery mode, and maternal gestational week (± 1 week). Baseline perinatal and pathological indicators were compared between the two groups. Univariate analysis followed by multivariate logistic regression was performed to screen independent risk factors for positive UCBC. Stratified subgroup analyses were further implemented to compare pathogen spectrum differences under distinct HCA severity and FIR status. Results The incidence rates of moderate or severe HCA, FIR, clinical chorioamnionitis, maternal prenatal temperature ≥ 38.0℃, maternal prenatal pathogenic infection, and maternal pregnancy complicated by cervical incompetence in the UCBC positive group were significantly higher than in the UCBC negative group ( P < 0.05), and the maternal age was older ( P < 0.05). Multivariate logistic regression analysis identified that FIR(OR = 6.253, 95% CI: 2.704–14.458, P < 0.001) and prenatal pathogenic infection (OR = 5.904, 95% CI: 2.819–12.368, P < 0.001) were independent risk factors for positive UCBC. A total of 86 pathogenic strains were isolated from 81 positive UCBC specimens (5 cases of polymicrobial infection), including 51 Gram-positive strains (59.3%), mainly Enterococcus faecalis (14.0%), Group B Streptococcus (7.0%) and Streptococcus mitis (7.0%); 35 Gram-negative strains (40.7%), mainly Escherichia coli ( E. coli ) (29.1%). Among the 81 cases with positive UCBC, 36 (44.4%) exhibited normal placental pathology or mild HCA, and 45 (55.6%) presented moderate or severe HCA; no statistically significant intergroup difference was observed ( P > 0.05). For the 25 cases with E. coli infection, 11 (44.0%) showed normal placental pathology or mild HCA, while 14 (56.0%) had moderate or severe HCA, with no significant difference between groups ( P > 0.05). Of the 45 cases with moderate or severe HCA, 40 (88.9%) were complicated with FIR, among which E. coli infection was the predominant pathogen (13/40). All cases with polymicrobial infection or Listeriosia monocytogenes ( L. monocytogenes ) infection were pathologically confirmed as moderate or severe HCA combined with FIR. Conclusion FIR and maternal prenatal infectious pathogens are independent predictors of positive UCBC. Moderate or severe HCA concurrent with FIR was prone to occur in cases infected with E. coli , L. monocytogenes , or polymicrobial pathogens, indicating that intrauterine inflammatory reactions induced by these bacteria are severe and warrant close clinical vigilance.