Bacterial vaginosis is the most common vaginal infection in women of reproductive age, affecting roughly 29% of women in the United States at any given time. That translates to about 21 million women, based on national survey data. Despite those numbers, nearly half of all cases produce no noticeable symptoms, which means millions of women have BV without knowing it.
Prevalence in the US and Worldwide
A nationally representative study using data from the CDC found that 29.2% of US women aged 14 to 49 tested positive for BV. That makes it more common than yeast infections, which tend to get more attention. The high rate is partly explained by how many cases fly under the radar: in one clinical study, 48% of women who tested positive for BV reported no symptoms at all.
Globally, the picture is surprisingly consistent. A large systematic review found BV prevalence ranging from 23% to 29% across every major world region. Europe and Central Asia had the lowest rate at 23%, while South Asia had the highest at 29%. North America fell at 27%. Sub-Saharan Africa, often assumed to have far higher rates, came in at 25% in general population studies. BV is not concentrated in any one part of the world; it is genuinely everywhere.
Significant Racial and Ethnic Disparities
Within the US, the averages mask a stark disparity. Black women have a BV prevalence of 51.6%, more than double the rate among white, non-Hispanic women at 23.2%. Mexican American women fall between the two at 32.1%. These gaps are among the largest documented disparities in reproductive health, and researchers believe they reflect a combination of factors including differences in vaginal microbiome composition, socioeconomic stressors, and unequal access to care rather than any single biological cause.
How Age Affects Your Risk
BV is overwhelmingly a condition of the reproductive years. Women who are still menstruating and perimenopausal women have similar rates, around 10 to 11% in studies using strict lab-based diagnostic criteria. After menopause, prevalence drops significantly to about 6%. That decline holds regardless of whether a woman uses hormone replacement therapy (5.4% with HRT vs. 6.3% without). The shift in vaginal bacteria that comes with lower estrogen levels after menopause appears to make BV less likely, not more, which surprises many people.
BV During Pregnancy
Prevalence in pregnant women ranges widely depending on the population studied, from about 12% to 49% globally. In one hospital-based study, 19% of pregnant women were diagnosed with BV over a one-year period. The concern during pregnancy is not the infection itself but what it can trigger. In that same study, 29 of the 55 women with BV delivered prematurely, compared to just 6 premature births among the 240 women without BV. That’s a dramatic difference.
BV during pregnancy has been linked to preterm birth, premature rupture of membranes, miscarriage, and postpartum uterine infections. The disruption to the normal vaginal bacterial balance appears to allow inflammation that can weaken the membranes surrounding the fetus. This is one reason prenatal screening for BV is a topic of ongoing clinical discussion, particularly for women with a history of preterm delivery.
What Increases Your Risk
BV develops when the balance of bacteria in the vagina shifts away from the protective species (primarily lactobacilli) toward a mix of other organisms. Several behaviors are consistently linked to that shift. Douching is one of the strongest risk factors because it directly disrupts the vaginal environment. Having new or multiple sexual partners also increases risk, as does not using condoms. BV is not classified as a sexually transmitted infection, but sexual activity clearly plays a role in triggering it.
Other contributing factors include antibiotic use (which can wipe out protective bacteria along with harmful ones), smoking, and using scented soaps or products in the vaginal area. Some women develop BV repeatedly without an obvious trigger, which points to individual differences in vaginal microbiome resilience.
Recurrence Is Extremely Common
One of the most frustrating aspects of BV is how often it comes back. More than 50% of women who are successfully treated experience a recurrence within three to six months. Within a full year, recurrence rates climb as high as 69%. This is not a failure of treatment so much as a reflection of how difficult it is to permanently restore the vaginal bacterial balance once it has been disrupted.
For many women, BV becomes a recurring cycle that significantly affects quality of life. The odor, discharge, and discomfort can cause embarrassment, anxiety about sexual relationships, and a sense of helplessness when infections keep returning despite following treatment correctly. The high recurrence rate has driven substantial interest in alternative and supplemental approaches, including vaginal probiotics and longer courses of treatment, though no strategy has solved the problem definitively.
BV Raises the Risk of Other Infections
Beyond the symptoms themselves, BV creates vulnerability to other infections. The disrupted vaginal environment makes it easier for sexually transmitted infections to take hold. Prospective studies have shown that women with BV face higher odds of acquiring HIV, herpes (HSV-2), chlamydia, gonorrhea, and trichomoniasis. BV is also implicated in pelvic inflammatory disease, which can cause chronic pain and fertility problems if untreated.
The mechanism is straightforward: the lactobacilli that normally dominate a healthy vagina produce lactic acid and other compounds that create a hostile environment for incoming pathogens. When BV reduces those protective bacteria, the vaginal lining becomes more susceptible to infection and inflammation. This is one reason public health experts view BV not just as a nuisance condition but as a meaningful factor in STI transmission at the population level.
Why Many Cases Go Undiagnosed
With nearly half of BV cases producing no symptoms, many women never seek testing and never receive a diagnosis. Even among women who do have symptoms, the signs can be subtle or mistaken for something else. The hallmark is a thin, grayish-white discharge with a fishy odor, particularly noticeable after sex. But discharge alone is common and can have many causes, so women often dismiss it or treat it with over-the-counter yeast infection products that do nothing for BV.
Clinicians diagnose BV using either a bedside evaluation (looking for at least three of four clinical signs including elevated vaginal pH, characteristic discharge, fishy odor on a chemical test, and the presence of “clue cells” under a microscope) or a lab-based scoring system that examines the types of bacteria present in a vaginal sample. The lab method is considered the gold standard for research studies but is less practical in everyday clinical settings, where the bedside approach is more common. Neither method is routinely performed at annual exams unless a woman reports symptoms, which contributes to the large number of undetected cases.