Bacterial vaginosis (BV) is a common yet poorly understood condition, in which the balance of bacteria inside the vagina becomes disrupted.
BV doesn't usually cause any vaginal soreness or itching, but often causes unusual vaginal discharge. If you have the condition, your discharge may:
- develop a strong fishy smell, particularly after sexual intercourse
- become white or grey
- become thin and watery
BV isn't serious for the vast majority of women, although it may be a concern if symptoms of BV develop in pregnancy and you have a history of pregnancy-related complications.
Around half of women with bacterial vaginosis have no symptoms.
When to seek medical advice
See your GP or visit a sexual health or genitourinary medicine (GUM) clinic if you notice any abnormal discharge from your vagina, especially if you're pregnant. It's important to get this checked to rule out other infections and prevent complications.
Your doctor will ask about your symptoms and may examine your vagina. In some cases, a small sample of the vaginal discharge will be taken using a plastic loop or swab, so it can be examined for signs of BV.
Read more about diagnosing bacterial vaginosis.
Why it happens
The vagina naturally contains a mix of many different bacteria. In cases of BV, the number of certain bacteria increases, affecting the balance of chemicals in the vagina.
What leads to these changes in the levels of bacteria is not clear. BV isn't classified as a sexually transmitted infection (STI), but you're at a higher risk of developing the condition if you're sexually active.
Women with BV may be able to pass the condition to other women they have sex with, although it's not clear how this happens.
There's no evidence to suggest the bacteria causing BV can affect male sexual partners.
There are also a number of other factors that can increase your risk of developing BV, including:
BV is more common in women who use a coil for contraception and those who perform vaginal douching (cleaning out the vagina).
Read more about the causes of bacterial vaginosis.
BV can usually be successfully treated using a short course of antibiotic tablets or an antibiotic gel you apply inside your vagina.
In most cases, you'll be prescribed antibiotic tablets to take twice a day for five to seven days.
However, it's common for BV to return. More than half of women successfully treated with BV find their symptoms return, usually within three months. Women who have frequent episodes of BV may be referred to a GUM specialist.
Read more about treating bacterial vaginosis.
If BV develops in pregnancy, it may increase the risk of pregnancy-related complications, such as premature birth or miscarriage. However, this risk is small and appears more significant for women who have had these complications in a previous pregnancy. BV causes no problems in the vast majority of pregnancies.
As a precaution, you should contact your GP or GUM clinic if you're pregnant and you begin to have vaginal discharge (although discharge can be a normal part of pregnancy).
Bacterial vaginosis can also increase your risk of getting some STIs.
Read more about the complications of bacterial vaginosis.
The causes of BV aren't fully understood, so it's not possible to completely prevent it. However, you may be able to lower your risk of developing the condition if you avoid:
- using scented soaps, perfumed bubble bath and antiseptic bath liquids
- using vaginal deodorant
- vaginal douching
- using strong detergents to wash your underwear
These can upset the natural bacterial balance in your vagina, making it more likely that you'll develop BV.