BV stands for bacterial vaginosis, a common vaginal condition caused by an imbalance in the bacteria that naturally live in the vagina. It affects roughly 23 to 29 percent of women of reproductive age worldwide, making it the most frequent cause of abnormal vaginal discharge. Despite how common it is, BV is widely misunderstood and often confused with yeast infections.
What Happens Inside the Vagina During BV
A healthy vagina is home to a community of bacteria dominated by a type called Lactobacilli. These bacteria produce lactic acid, which keeps the vaginal environment slightly acidic (a pH below 4.5) and inhospitable to harmful microbes. BV develops when Lactobacilli are suddenly overtaken by a mix of other bacteria that normally exist in small numbers, including species like Gardnerella vaginalis, Atopobium vaginae, Prevotella, and Mobiluncus.
This bacterial takeover shifts the vaginal pH above 4.5, creating a more alkaline environment. The exact trigger for this shift remains unknown. Researchers understand what BV looks like at a microbial level but have not pinpointed why the balance tips in the first place. BV is not considered a sexually transmitted infection, though sexual activity can play a role in disrupting the bacterial balance.
Symptoms and How BV Feels
Many people with BV have no symptoms at all. When symptoms do appear, the most recognizable one is a thin, grayish, sometimes foamy vaginal discharge with a distinct fishy smell. The odor is often more noticeable after sex. Some people also experience mild itching or burning during urination, though these symptoms are less common than the discharge itself.
BV is frequently confused with yeast infections, but the two look and feel quite different. Yeast infections produce thick, white, clumpy discharge (often compared to cottage cheese) with no strong odor, and tend to cause more intense itching and irritation. BV discharge, by contrast, is thinner, grayish, and characterized by that fishy smell. If you’re unsure which you’re dealing with, the distinction matters because they require different treatments.
Risk Factors
Several behaviors increase the likelihood of developing BV. Douching is one of the most well-established risk factors because it directly disrupts the vaginal bacterial balance. Having new or multiple sexual partners and not using condoms also raise the risk. The CDC identifies these three factors as the primary behaviors that upset normal vaginal flora.
BV can recur frequently. Some people deal with repeated episodes even after successful treatment, which suggests that the underlying vulnerability in their vaginal microbiome persists beyond any single course of treatment.
How BV Is Diagnosed
Doctors typically diagnose BV using a set of clinical signs known as the Amsel criteria. A diagnosis requires at least three of the following four findings:
- Thin, milklike discharge that coats the vaginal walls smoothly
- Clue cells visible under a microscope (vaginal cells covered in bacteria, giving them a stippled appearance)
- Vaginal pH above 4.5
- Fishy odor when the discharge is exposed to a chemical solution in the office
A lab-based method called the Nugent scoring system can also confirm the diagnosis. This involves examining a vaginal swab under a microscope and scoring the types of bacteria present on a scale of 0 to 10. A score of 0 to 3 indicates normal flora, 4 to 6 falls into an intermediate zone that can be hard to interpret, and 7 to 10 confirms BV. In practice, many clinicians rely on the Amsel criteria during a routine office visit rather than sending samples to a lab.
Treatment
BV is treated with prescription antibiotics, available in both oral and vaginal forms. Treatment typically lasts five to seven days. Most people see symptoms resolve within a few days of starting medication, though it’s important to complete the full course.
The challenge with BV is recurrence. A significant number of people experience BV again within months of treatment. This has led to growing interest in longer-term management strategies, including extended courses of vaginal antibiotics and probiotics, though the evidence for probiotics remains mixed.
Why Untreated BV Matters
For many people, BV is a nuisance rather than a serious health threat. But leaving it untreated carries real risks, particularly during pregnancy. One study found that pregnant women with BV had a preterm birth rate of 22.7 percent (delivery before 34 weeks) compared to 6.2 percent in women without BV. Babies born to mothers with BV also had lower birth weights, higher rates of respiratory distress, and were more likely to need intensive care after delivery.
Outside of pregnancy, untreated BV increases susceptibility to sexually transmitted infections. The disrupted vaginal environment makes it easier for infections like HIV, chlamydia, and gonorrhea to take hold. BV can also increase the risk of pelvic inflammatory disease, a condition that can affect fertility if left untreated. These complications are why treatment is recommended even when symptoms feel manageable.