Bacterial vaginosis is caused by an imbalance of the organisms (flora) that
naturally exist in the
vagina. Normally, about 95% of vaginal flora are
lactobacillus bacteria. (These types are unique to humans, different from the
lactobacillus in yogurt.) These lactobacilli help keep the vaginal
pH level low and prevent overgrowth of other types of
organisms. Women with bacterial vaginosis have fewer lactobacillus organisms
than normal and more of other types of bacteria. Experts do not yet understand what causes this imbalance.
specific cause isn't known, a number of health and lifestyle factors have been
linked to bacterial vaginosis. For more information, see the What Increases
Your Risk section of this topic.