Recognizable? Discharge that's different from what you're used to, a smell that suddenly stands out, or just the feeling that something isn't quite right. If this sounds familiar, you're definitely not the only one. Bacterial vaginosis, often shortened to BV, is one of the most common causes of altered vaginal discharge in women of reproductive age. Worldwide, BV is estimated to affect approximately 23 to 29 percent of women.
A disrupted balance
BV is not an infection with one clear culprit. It's a disruption of the balance in the vaginal microbiome.
Normally, the vaginal flora is dominated by lactobacilli. These are bacteria that produce, among other things, lactic acid, contributing to an acidic vaginal environment. That acidic environment helps maintain the balance and makes it harder for certain unwanted bacteria to overgrow.
With BV, the number of lactobacilli decreases. At the same time, other bacteria, particularly anaerobic ones, get more room to grow. Think of species such as Gardnerella vaginalis, Prevotella, Atopobium, and Mobiluncus. So it's not about one bacterium suddenly causing everything, but rather a shift in the composition of the vaginal flora.
What you might notice, and what you might not
The most well-known signs of BV are thin, gray-white discharge and a noticeable, sometimes fishy odor. That odor can be more noticeable around or after sex, but can also stand out at other times.
When diagnosing BV, doctors don't just look at symptoms. They may also check the vagina's acidity, the odor of the discharge, and, when examined under a microscope, whether vaginal cells covered in bacteria are visible. These are part of what's known as the Amsel criteria, a method used in practice to identify BV. Important to know: not everyone with BV has symptoms. About half of women with BV notice little to nothing. As a result, BV is sometimes discovered by chance, for example during an examination for another reason.
Why does BV develop?
The precise cause of BV still isn't fully understood. That's also why BV can sometimes be frustrating: you can have symptoms, get treated, and still find that the balance becomes disrupted again later.
Research does show that various factors are associated with a higher likelihood of BV. Think of vaginal douching, smoking, antibiotic use, hormonal fluctuations, menstruation, and sexual activity. A new partner or multiple sexual partners are also mentioned in studies as factors that may be associated with BV. That doesn't mean BV is "your own fault." Nor does it mean BV is always caused by sex. The vaginal flora is a dynamic ecosystem that can change due to many different internal and external factors.
Is BV an STI?
BV is generally not seen as an STI in the classic sense of the word. With an STI, there's often a specific pathogen that's transmitted from one person to another. With BV, it's different: it's about a broader disruption of the vaginal flora, in which multiple bacterial species can be involved.
At the same time, sexual activity can indeed influence the vaginal balance. Semen, for instance, has a different pH value than the vagina, and contact with a partner can also affect which bacteria are present. Research shows that BV occurs more often in women with a new partner or multiple partners, and that partner-related factors may play a role in recurrent BV.
So it's better to think of BV as a condition where sex and partners can influence the vaginal balance, without BV being the same thing as a classic STI.
Why it's worth involving a doctor
BV symptoms can resemble other vaginal complaints, such as a yeast infection or an STI. Think of changed discharge, odor, itching, or irritation. This can sometimes make it difficult to assess yourself what exactly is going on.
A doctor can help distinguish between BV, a yeast infection, an STI, or another cause. This can be done through, for example, a physical exam, pH measurement, microscopic examination, or a lab test.
That's not just reassuring in terms of knowing where you stand. Research has also linked BV to increased susceptibility to certain infections and, during pregnancy, to adverse pregnancy outcomes such as preterm birth. This doesn't mean everyone with BV will experience serious consequences, but it does mean persistent or recurring symptoms deserve to be taken seriously.
Why BV sometimes comes back
BV can be stubborn. The standard treatment often consists of antibiotics, such as metronidazole or clindamycine. That treatment can work well, but in some women, the symptoms return. Various studies describe high recurrence rates, sometimes affecting more than half of women within a year of treatment. That doesn't mean you're doing anything wrong. Researchers believe recurrent BV may be related to, among other things, the difficulty of restoring a lactobacilli-dominant flora, biofilms in which bacteria can hide, or renewed disruption of the vaginal balance. This is exactly why it's important not to ignore recurring symptoms or keep trying to solve them yourself indefinitely. If symptoms keep coming back, it's a good idea to have things checked again.
