A new study suggests a key to preventing recurrences of bacterial vaginosis (BV) in women might be to treat their male partners.

A healthy vagina has a balance between many types of bacteria, and the “helpful” bacteria keeps the “less helpful” bacteria in check. Sometimes the “less helpful” bacteria grow too fast, and this imbalance can result in a common condition known as bacterial vaginosis. Many people with BV don’t have symptoms but those who do might experience an unusual vaginal discharge or fishy odor, vaginal itching, or burning when they pee.

It isn’t clear exactly why BV develops or why it often comes back after treatment. Douching, having a copper IUD or even new sex partners have been mentioned as possibly associated. But research published in the New England Journal of Medicine offers more evidence that BV is strongly linked with sexual activity. (A note on douching: it isn’t clear if women develop BV because of douching or if they douche because they are already have BV and are trying to get relief from symptoms.)

Study Shows Impact of Treating Male Partners

The study was done with couples in which a woman was diagnosed with BV, had a male partner, and was in a relationship where she and her partner only had sex with each other. Eighty-one couples were assigned to a group where both partners were treated—the woman with oral antibiotics and the male with both oral antibiotics and an antibiotic cream applied to the skin of the penis. Eighty-three additional couples were in a group where only the woman was treated. (The current standard of care with BV only involves treating the partner who is diagnosed.)

In the group where both partners were treated, BV recurred in 35% of the women, compared to 63% in the group where only the woman received treatment. This  difference was so striking that the study stopped early so all participants could take advantage of treatment.

Is BV and STI?

Linking BV to sexual activity has been gaining traction, but does that mean it should be considered a sexually transmitted infection, or STI? Like relationships themselves, it’s complicated.

Patty Cason, RN, MS, FNP-BC, a board-certified family nurse practitioner specializing in reproductive and sexual health, suggests we think of BV as sexually “associated”: “It’s long been known the bacteria linked with BV are found on the penis, often below the foreskin, and that’s predictive of a partner’s risk of BV. These are naturally occurring bacteria, however, unlike the infections we classify as STIs. This exchange of bacteria that leads to BV can occur even in couples where both partners have only been sexual with each other.”

Ms. Cason says she’s excited about the new data because previously we lacked evidence that treating male partners changes the recurrence rate in women. She says treating partners is likely beneficial but adds, “There’s still much about BV we don’t know, and this includes why it occurs in the first place. In my practice, though, I’ve rarely seen a case in someone who has never had sex.” Ms. Cason says the aspect of BV and “sexual association” is complex and may go beyond a simple exchange of organisms: “The vagina is naturally acidic, semen less so, and the presence of semen can alter the vaginal pH in a way that makes the environment more welcoming for the bacteria that cause BV.”

Learn more about BV, including prevention, diagnosis, and current treatment options.