Bacterial vaginosis is caused by an imbalance in your vagina’s normal bacteria.
When the pH level in your vagina is unbalanced, certain normal bacteria can overgrow, leading to bacterial vaginosis.
Bacterial vaginosis is not a sexually transmissible infection (STI).
Anything that changes the balance of the bacteria in your vagina can cause bacterial vaginosis. Sometimes sex with a new person, or increased sexual activity, can lead to bacterial vaginosis. At the same time, many people who have never had sex will get bacterial vaginosis.