Risk factors of chronic endometritis in women who have undergone hysteroscopy: a prospective nested case–control study

There is limited research on risk factors for chronic endometritis regarding reproductive history and clinical symptoms. Thus, this nested case-control study identified risk factors for chronic endometritis in women who have undergone hysteroscopy. Endometrial tissue sections were obtained from 502 women with intrauterine disorders who underwent hysteroscopy. Chronic endometritis was diagnosed via CD138 immunostaining. The women were divided into two groups: 271 women without chronic endometritis and 231 women with chronic endometritis. The prevalence of chronic endometritis was 46%. Univariate logistic regression revealed that prolonged menstruation and intermenstrual bleeding were associated with chronic endometritis, and subsequent multivariate logistic regression analyses showed that these were further independently associated. With univariable logistic regression, the gravidity and abortion history were correlated with chronic endometritis; however, no significant correlation was found with the adjusted odds ratio (OR) of 0.74 (95% confidence interval [CI] 0.46-1.19) or 0.76 (95% CI 0.58-1.11), respectively. No significant correlation was found between caesarean section history and the rates of chronic endometritis. No significant difference was found in all other variables between the three groups with > 5, ≤ 5 plasma cells and in a unknown group. Prolonged menstruation and intermenstrual bleeding were risk factors associated with chronic endometritis. Chronic endometritis should be considered and CD138 immunohistochemical examination should be recommended in women with these symptoms.