Bacterial Vaginosis-Associated Bacteria and Uterine Fibroids: A Nested Case-Control Study

Background Reproductive tract infections are hypothesized to influence uterine fibroid development, yet few studies have investigated the common condition of bacterial vaginosis (BV). The literature is currently limited to data using self-report of BV. Methods We conducted a nested case-control study of 200 women (100 cases and 100 controls) from a large study of 23- to 35-year-old African American women, 1310 of whom were fibroid-free and prospectively followed up for 5 years to identify incident fibroids with standardized ultrasound examinations. We used quantitative polymerase chain reaction, an objective molecular method, to assess 9 BV-associated and 4 Lactobacillus species from vaginal swab specimens. We used hierarchical logistic regression to compute odds ratios and 95% confidence intervals to examine associations between bacterial species (both individually and grouped as (1) "optimal" Lactobacillus and (2) BV-associated species) with fibroid incidence and number. We also examined vaginal imbalance (quantitatively more BV-associated bacteria than optimal Lactobacilli). Results Contrary to our hypothesis, we found no increase in fibroid incidence or number among women with more BV-associated bacteria. High imbalance (only BV-associated bacteria, no optimal Lactobacillus bacteria) was actually inversely associated with fibroid incidence (odds ratio, 0.38; 95% confidence interval, 0.17-0.81). Conclusions This is the first study of ultrasound-detected incident fibroids and molecular vaginal bacterial assessment. We found no evidence that BV-associated bacteria increase the risk of fibroid incidence or number.