How Bacterial Vaginosis (BV) is Acquired
BV is primarily associated with sexual activity, though the exact mechanism of acquisition remains incompletely understood. Women who have never been sexually active are rarely affected 1.
Key Risk Factors for Acquisition
Sexual Activity-Related Factors
- Multiple sex partners - consistently associated with BV acquisition 1
- New sex partner with BV history - increases risk 3.6-fold 2
- Receptive oral-vulvovaginal sex - shows dose-response relationship with increasing episodes 2
- Unprotected intercourse - may neutralize vaginal acidity through ejaculate, allowing replacement of protective Lactobacillus with BV-associated bacteria 3
Non-Sexual Risk Factors
- Douching - disrupts normal vaginal flora 1
- Lack of vaginal lactobacilli - absence of protective bacteria 1
The Biological Mechanism
BV develops when normal hydrogen peroxide-producing Lactobacillus species in the vagina are replaced by high concentrations of anaerobic bacteria (including Prevotella, Mobiluncus, Gardnerella vaginalis, and Mycoplasma hominis) 1.
Important caveat: While BV is strongly associated with sexual activity, it is not classified as exclusively a sexually transmitted disease 4. The exact causative pathogen has never been identified, and whether BV results from acquisition of a sexually transmitted pathogen remains unclear 1, 5.
Evidence for Sexual Transmission
Recent research provides compelling evidence for sexual transmission:
- Women who acquire BV are more likely to have extravaginal colonization (oral cavity, anal) with BV-associated bacteria before vaginal infection develops 6
- Detection of specific bacteria (G. vaginalis, Leptotrichia/Sneathia) in oral or anal samples predicts subsequent vaginal BV 6
- Male partner treatment reduces BV recurrence rates 7, 8
Clinical Pitfall
Partner treatment is NOT routinely recommended - treatment of male sex partners has not been shown to prevent BV recurrence in standard practice 1, 4, though recent trials suggest this may warrant reconsideration 7, 8.