Few microorganisms associated with bacterial vaginosis may constitute the pathologic core: a population-based microbiologic study among 3596 pregnant women.

Objective: To evaluate the association between various microorganisms isolated from the genital tract in pregnant women with bacterial vaginosis.
Study Design: A cross-sectional population-based study among pregnant women addressed at their first antenatal visit before 24 full gestational weeks from the referring area of the Department of Obstetrics and Gynecology at Odense University Hospital, Denmark, from November 1992 to February 1994. The main outcome measures were prevalence of various microorganisms and statistical estimates of interactions (crude, adjusted, and relative odds ratios) between the microorganisms isolated from the lower genital tract in pregnant women with and without clinical diagnosis of bacterial vaginosis.
Results: Three thousand five hundred ninety-six (3596) pregnant women were asked to participate. Of the 3596 pregnant women 3174 (88.4%) agreed to participate before 24 full gestational weeks. After controlling for the presence of other microorganisms, strong associations between Gardnerella vaginalis, anaerobic bacteria, Mycoplasma hominis, and present bacterial vaginosis were found. Similarly Lactobacillus spp. were found to be associated with the absence of bacterial vaginosis. The combination of G. vaginalis and anaerobic bacteria and/or M. hominis was found in 59.6% of the cases with bacterial vaginosis and in 3.9% of the cases without bacterial vaginosis (odds ratio 36.4, 95% confidence interval 27.8 to 47.8). The crude odds ratio was found to be as high as 74.8 (95% confidence interval 32.3 to 174.1) when the combination of G. vaginalis, M. hominis, anaerobic bacteria, and no Lactobacillus spp. was associated with bacterial vaginosis.
Conclusion: There is a microbial foundation for bacterial vaginosis, and it is possibly due to an intermicrobial interaction in which the microorganisms G. vaginalis, anaerobic bacteria, and M. hominis are dominating, indicating that these constitute the pathologic core of bacterial vaginosis.