Objectives We sought to determine whether the relationship between a history of vaginal douching and pelvic inflammatory disease (PID) is mediated by endometrial infection with one or more novel bacterial vaginosis (BV)-associated organisms among Atopobium vaginae, the BV-associated bacterium 1 (BVAB1), neathia (Leptotrichia) amnionii and Sneathia sanguinegens.
Methods We first conducted log-binomial regression analyses to identify risk factors for endometrial infection in 535 adolescent and adult women with clinically suspected PID in the PID Evaluation and Clinical Health (PEACH) study. We then examined whether endometrial infection by the BV-associated organisms mediated the association between a history of vaginal douching and histologically confirmed PID using inverse probability weighted marginal structural models.
Results Vaginal douching was significantly associated with endometrial infection with one or more of the targeted BV-associated organisms (relative risk (RR) 1.21, 95% CI: 1.08 to 1.35). The total effect estimate suggested that vaginal douching increased the risk of endometritis by 24% (RR 1.24, 95% CI: 1.03 to 1.49). The controlled direct effect of this association was attenuated with endometrial infection by one or more BV-associated organisms (adjusted RR (aRR) 1.00, 95% CI: 0.57 to 1.74) and endometrial infection by all four BV-associated organisms (aRR 0.95, 95% CI: 0.53 to 1.70) as intermediate variables.
Conclusions Endometrial infection with one or more of the novel BV-associated organisms partially mediated the relationship between vaginal douching and histologically confirmed endometritis in the PEACH study. Frequent vaginal douching may confer risk for endometritis through increasing the risk of endometrial infection by novel-BV-associated organisms. Other potential pathways should be explored.
- pelvic inflammatory disease
- bacterial vaginosis
- epidemiology (general)
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Handling editor Anna Maria Geretti
Contributors All authors have seen and approved the manuscript, have contributed significantly to the work, and do not have conflicts of interest to report.
Funding This work was supported by the National Institute of Allergy and Infectious Diseases at the National Institutes of Health [R01AI073940 to C.L.H.]
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval University of Pittsburgh Institutional Review Board (IRB number: 0608052).
Provenance and peer review Not commissioned; internally peer reviewed.
Data availability statement Data are available upon reasonable request with approval from the corresponding author at the contact provided.