Vaginal microbial ecology in abnormal uterine bleeding: compositional alterations and pathophysiological impact as early predictors of secondary infection

Background Abnormal uterine bleeding (AUB) is a common gynecological condition that may disrupt the vaginal acidic environment and self-cleaning mechanisms, thereby predisposing patients to secondary vaginal infections. However, the predictive value of routine morphological and functional parameters for subsequent infection remains unclear. Objective To study the current status of vaginal microecology morphology and function in patients with AUB, and to analyze its impact on secondary infections and its significance for early warning. Methods A prospective study included 128 AUB patients (April 2021–April 2023) without initial vaginal infection. Vaginal secretions were collected for morphological and functional analysis. Patients were followed for 6 months and divided into infected (n=51) and non-infected (n=77) groups. Comparisons and ROC curve analysis were performed to evaluate predictive value. Results In the infected group, vaginal bacteria concentration was higher. Proportions of abnormal pH, H 2 O 2 secretion, positive leukocyte esterase, high Nugent score, and more leukocytes in vaginal secretions were higher, while the proportion of gram - positive bacteria was lower. Vaginal microbiota density grade I + IV, abnormal pH, H 2 O 2 secretion, positive leukocyte esterase, Nugent score, and leukocyte count were positively correlated with secondary infection, and gram - positive bacteria were negatively correlated. The combined prediction of secondary infection had an AUC of 0.902, with 88.24% sensitivity and 76.62% specificity. Conclusion The vaginal microecology of AUB patients is unbalanced, and the incidence of secondary infection is high, which may be related to the concentration of vaginal flora I+IV, the dominant bacteria being Gram-positive bacteria, abnormal H 2 O 2 secretion, Nugent score, abnormal pH value, positive leukocyte esterase, and leukocyte count in vaginal secretions. The combined prediction of secondary infection of patients has certain reference value.