Bacterial vaginosis

Bacterial vaginosis (BV) is an imbalance of the usual bacteria found in a woman’s vagina. It causes an abnormal vaginal discharge which can smell fishy and unpleasant.

The vagina

The vagina is a tube of muscle that runs from the cervix (the opening of the womb) to the vulva (the external sexual organs). Some types of bacteria are always present in the vagina to keep it healthy.

If a woman has BV, the usual balance of bacteria changes. The vagina will have:

• less lactobacilli (lactic acid bacteria),
• an overgrowth of other types of bacteria, and
• a higher pH (the measure of acidity and alkalinity), making it more alkaline.

How common is bacterial vaginosis?

Bacterial vaginosis is the most common cause of abnormal vaginal discharge. In the UK, around 12-30% of women may be affected. Among pregnant women, this figure may be around 20%.

The cause of BV is not fully understood, although some factors make it more likely. While BV is not a sexually transmitted infection (STI), it is more common among people who are sexually active. Other factors that contribute to BV include smoking and using certain hygiene products.

Outlook

BV can appear and disappear without any reason, and around half of all women with BV are asymptomatic (do not have any symptoms). If there are no symptoms, treatment is not necessary. Where there are symptoms, antibiotics may be recommended.

Treatment is effective in up to 90% of BV cases, although it is quite common for BV to reoccur. Around 25% of women will have BV again within one month and will need to be treated with antibiotics again.

BV has been linked to a number of other conditions. It may increase the risk of having some STIs, such as gonorrhoea. Pregnant women with BV may also be at increased risk of developing complications, such as a preterm birth (when a baby is born before the 37th week of the pregnancy).