Objective To explore the risk factors for histologic chorioamnionitis (HCA) in patients with preterm premature rupture of membranes (PPROM) based on clinical characteristics and inflammatory indicators.

Methods A retrospective analysis was conducted on the clinical data of 108 patients with PPROM. According to the postpartum pathological results, they were divided into HCA group (32 cases) and non-HCA group (76 cases). The clinical characteristics and laboratory indicator levels of the two groups were compared. Logistic regression analysis was used to screen the risk factors for HCA in patients with PPROM. Receiver operating characteristic (ROC) curves were plotted to analyze the predictive efficacy of independent risk factors and a combined model for the occurrence of HCA in patientswith PPROM.

Results The gestational age at membrane rupture in the HCA group was shorter than that in the non-HCA group. The proportions of patients with a rupture-to-delivery interval≥24 h, concurrent vaginal infection, prenatal fever, positive group B Streptococcus (GBS), and severe amniotic fluid contamination were all higher in the HCA group than those in the non-HCA group. The levels of C-reactive protein (CRP), neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and monocyte-to-lymphocyte ratio (MLR) were all higher in the HCA group than in the non-HCA group, with statistically significant differences (P < 0.05). The results of multivariate Logistic regression analysis showed that a rupture-to-delivery interval≥24 h, prenatal fever, and an elevated NLR were independent risk factors for the occurrence of HCA in patients with PPROM(P < 0.05). The ROC curves showed that the areas under the curves (AUC) for predicting the occurrence of HCA in patients with PPROM by rupture-to-delivery interval, prenatal fever, and NLR were 0.817, 0.735, and 0.840, respectively, with sensitivities of 75.00%, 71.88%, and 84.38%, respectively. The AUC predicted by the combined model was 0.906, with a sensitivity of 86.80%, and its predictive efficacy was significantly better than that of individual indicator (P < 0.05).

Conclusion A rupture-to-delivery interval≥24 h, prenatal fever, and an elevated NLR are independent risk factors for the occurrence of HCA in patients with PPROM. Clinically, these indicators can be monitored to early identify the risk of HCA occurrence, thereby guiding the use of antimicrobial agents or the selection of the delivery timing.