Analysis of the prevalence of bacterial vaginosis and Chlamydia trachomatis infection in 6083 pregnant women at a hospital in Otaru, Japan.

Aim: Our aims were to evaluate the prevalence of bacterial vaginosis (BV), Chlamydia trachomatis (C. trachomatis) infection and Mobiluncus spp. infection among pregnant women in Otaru, Hokkaido, Japan according to the month and year of the first prenatal visit, and to evaluate their risk factors.
Methods: Six thousand and eighty-three pregnant women who were seen consecutively at our hospital between 1993 and 2000, were enrolled in the study. Vaginal and endocervical swabs were subjected to Gram stain and detection of C. trachomatis. Univariate and multivariate methods were used to investigate the association between each infection and potential risk factors including age, gravidity, parity, history of dilatation and curettage (D & C), and history of natural abortion.
Results: The annual rate of BV increased from 13.6% in 1993 to 21.4% in 2000. The annual rate of C. trachomatis infection was relatively constant. The prevalence of bacterial vaginosis, C. trachomatis infection and Mobiluncus spp. infection over the 8-year period was 18.2%, 4.2%, and 4.1%, respectively. The prevalence of the three infections was significantly higher among teenagers and among women with a history of D & C. The prevalence of C. trachomatis and Mobiluncus spp. infections was significantly higher among women with no history of delivery. BV was not associated with parity on multivariate analysis. The monthly prevalence of BV was significantly higher in May than in December, and the monthly prevalence of C. trachomatis infection was high in August.
Conclusion: The differences in the annual and monthly infection patterns between BV and C. trachomatis infection suggest that the etiologies of the two infections differ.