Bacterial Vaginosis (BV) is a common condition resulting from an imbalance in the bacteria within the vagina. A healthy vaginal environment is typically dominated by Lactobacillus species, which produce lactic acid to maintain a low pH. BV occurs when these protective bacteria are significantly reduced, allowing an overgrowth of other types of bacteria, such as Gardnerella vaginalis and Prevotella species. BV’s presence does not always align with a person’s experience of symptoms, raising the question of whether this imbalance can occur unnoticed.
The Prevalence of Asymptomatic BV
Bacterial Vaginosis is frequently a silent infection, occurring without discomfort or noticeable signs. Studies indicate that a significant majority of individuals diagnosed with BV, potentially as high as 84% in some populations, may not report any symptoms. This high rate of asymptomatic presentation emphasizes why BV is often difficult to detect without specific screening.
For many, the bacterial shift may be temporary, resolving naturally as the body re-establishes the dominance of Lactobacillus without medical intervention. This ability of the vaginal microbiome to self-correct contributes to undiagnosed or untreated instances. However, the lack of symptoms does not mean the condition is benign, especially when considering potential long-term risks.
Common Symptoms When BV is Noticeable
When bacterial overgrowth triggers a noticeable reaction, the clinical signs include an unusual vaginal discharge that is typically thin, milky, or grayish-white in color. This discharge often coats the vaginal walls uniformly, giving it a homogeneous appearance.
A strong, unpleasant “fishy” odor is caused by the release of volatile amines produced by the anaerobic bacteria. This odor often becomes more pronounced after sexual intercourse or during menstruation, as blood or semen can increase the vaginal pH, further triggering the release of these amines. While less common than with other types of vaginal infections, some individuals may also report mild burning during urination or irritation around the outer vaginal area.
Diagnosis and Screening for BV
Because BV frequently presents without complaints, healthcare providers rely on specific clinical and laboratory methods for identification. Diagnosis is often based on the Amsel criteria, which require the presence of at least three out of four specific findings. These criteria involve observing the characteristic thin, homogeneous discharge, measuring an elevated vaginal pH above 4.5, and performing a “whiff test” to detect the amine odor after adding potassium hydroxide to a discharge sample.
The most definitive criterion involves microscopic examination of a wet mount slide to identify “clue cells”—vaginal epithelial cells obscured by a layer of adherent bacteria. For a more objective and standardized assessment, the Gram stain-based Nugent scoring system is considered the gold standard. This method assigns a score from 0 to 10 by quantifying the relative abundance of protective Lactobacillus versus BV-associated bacteria, with a score of 7 to 10 confirming the diagnosis. Newer molecular tests, such as Polymerase Chain Reaction (PCR), are also increasingly used to detect the DNA of bacteria associated with BV, offering a highly sensitive way to screen for the presence of the causative organisms.
Health Risks Associated with Untreated BV
Even without noticeable discomfort, the underlying microbial imbalance can lead to several health complications. The loss of protective Lactobacillus species disrupts the natural barrier function of the vaginal environment, making the reproductive tract more susceptible to other infections. This disruption significantly increases the risk of acquiring sexually transmitted infections (STIs), including HIV, chlamydia, and gonorrhea.
BV-associated bacteria can also facilitate the ascent of pathogens into the upper reproductive tract, potentially leading to Pelvic Inflammatory Disease (PID). PID is a severe infection of the uterus, fallopian tubes, or ovaries that can result in long-term complications, such as chronic pelvic pain and infertility.
For pregnant individuals, untreated BV carries risks related to adverse pregnancy outcomes. The condition is associated with an elevated likelihood of preterm birth and the risk of delivering a low birth weight infant. BV has also been linked to premature rupture of membranes and postpartum endometritis. Screening is sometimes recommended for specific populations, such as pregnant individuals with a history of preterm labor.