A normal, healthy vagina is home to a variety of different bacteria. However, in Bacterial Vaginosis (BV) the balance is disturbed, and an overgrowth of some of these bacteria occurs. It’s not entirely clear why this happens. The most common symptom is a change in vaginal discharge, which may become white-grey in colour and may have a fishy smell. However, many women with BV do not have any symptoms at all (up to half of cases).