Bacterial vaginosis (BV) is a common yet poorly understood condition in which the balance of bacteria inside the vagina becomes disrupted.

BV does not cause any vaginal soreness or itching, but it often causes unusual vaginal discharge. If you have the condition, your discharge may:

  • develop a strong fishy smell, particularly after sexual intercourse
  • become a white or grey colour
  • become thin and watery

BV is not 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. In these cases, the condition does not pose any threat to your health or pregnancy.

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 are pregnant. It is important to get this checked to rule out other infections and prevent complications.

Your doctor will ask you about your symptoms and they 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.

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 is not classified as a sexually transmitted infection (STI), but you are at a higher risk of developing the condition if you are sexually active.

Women with BV may be able to pass the condition to other women they have sex with, although it is not clear how this happens.

There is no evidence to suggest that 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 using scented soaps or bubble baths, having an intrauterine device (IUD) fitted and using vaginal deodorant. BV is more common in women who use a coil for contraception and those who perform vaginal douching (cleaning out the vagina).

Treating bacterial vaginosis

BV can usually be successfully treated using a short course of antibiotic tablets or an antibiotic gel that 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 is common for BV to recur. More than half of women successfully treated with BV will find their symptoms return, usually within three months. Women who have frequent episodes of BV may be referred to a genitourinary medicine (GUM) specialist.


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 in women who have had these complications in an earlier pregnancy. BV causes no problems in the great majority of pregnancies.

As a precaution, you should contact your GP or GUM clinic if you are 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.

Preventing bacterial vaginosis

The causes of bacterial vaginosis are not fully understood, so it is 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 will develop BV.

This information has been sourced from NHS Choices.

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