Can Bacterial Vaginosis Be Transmitted Between Female Sexual Partners?
Yes, bacterial vaginosis (BV) can be transmitted between female sexual partners, and the evidence strongly supports sexual transmission as the predominant mode of BV acquisition in women who have sex with women (WSW).
Evidence for Sexual Transmission Between Women
The research evidence demonstrates clear patterns of sexual transmission:
Partner Concordance Studies
Multiple studies show striking concordance of BV between female sexual partners. In monogamous lesbian couples, when one partner has BV, the other partner is 19.7 times more likely to also have BV 1. Among 11 index women with BV in monogamous relationships, 72.7% had partners who also had BV, compared to only 10% when the index woman did not have BV 1.
Prospective Cohort Data
A large prospective cohort study of 298 women who have sex with women found that incident BV was strongly associated with:
- Having a new sexual partner (adjusted hazard ratio [AHR] 2.51) 2
- Having a partner with BV symptoms (AHR 3.99) 2
- Receptive oral-vulvovaginal sex (AHR 3.52) 2
Importantly, women enrolled with their BV-negative partner had a 74% reduced risk of developing BV (AHR 0.26), and these couples maintained concordant normal vaginal flora throughout follow-up 2.
Dose-Response Relationships
The evidence shows clear dose-response patterns consistent with sexual transmission:
- Increasing number of female sexual partners correlates with higher BV prevalence (OR 1.6 for ≥11 partners vs 1-5 partners) 3
- BV prevalence of 36-47.3% has been documented in WSW populations 4, 3
- Use of shared sexual accessories is independently associated with BV (OR 2.37) 4
Mechanisms of Transmission
The data suggest transmission occurs through:
- Exchange of vaginal fluids during sexual contact 4
- Sharing of sexual accessories without adequate cleaning between partners 4
- Oral-genital contact, particularly receptive oral sex 2, 5
Detection of BV-associated bacteria (BVAB) in women without BV predicted subsequent BV development weeks to months later, indicating that bacterial colonization precedes clinical disease 5.
Clinical Implications
Important Caveats
While the CDC guidelines from 1993-2002 state that "routine treatment of sex partners is not recommended" 6, 7, these guidelines were developed primarily based on heterosexual partnerships and male partner treatment studies. These recommendations do not adequately address female-to-female transmission.
The guideline evidence explicitly notes that treatment of male sex partners does not affect recurrence rates 6. However, this finding cannot be extrapolated to female partners, given the fundamental biological differences—women can harbor the same BV-associated organisms in their vaginal microbiota, while men do not have an equivalent reservoir.
Practical Recommendations for WSW
Given the strong epidemiological evidence:
Screen both partners when one presents with BV symptoms or diagnosis
Consider treating both partners when BV is diagnosed, particularly in monogamous relationships with recurrent BV, though this is not yet reflected in formal guidelines
Counsel patients about sexual transmission risk and protective measures:
- Avoid sharing sex toys, or clean thoroughly between partners
- Consider barrier methods during oral-genital contact
- Avoid sexual contact during active treatment
Monitor for concordant symptoms in regular female partners
Key Takeaway
The epidemiological evidence from multiple high-quality prospective and cross-sectional studies provides compelling support that BV is sexually transmitted between women 2, 5, 3, 1. The high concordance rates, dose-response relationships with sexual behaviors, and reduced risk when partnered with BV-negative women all point to sexual transmission as the primary mode of acquisition in WSW populations. This represents an important gap between current CDC guidelines (which focus on heterosexual transmission) and the emerging evidence specific to female same-sex partnerships.