Bacterial vaginosis (BV) is a common condition in which occcurs due to disruption of the balance of bacteria inside the vagina becomes disrupted.

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).


BV does not usually 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

Bacterial vaginosis (BV) can be treated successfully with antibiotics.
There is currently no evidence that probiotics, such as those found in some yoghurts, are of any benefit in treating or preventing BV.


Metronidazole is the most common and preferred antibiotic treatment for BV. It is available in three forms:

  • tablets to be taken twice a day for five to seven days
  • a single larger-dose tablet you take only once
  • a gel that you apply to your vagina once a day for five days

In most cases, metronidazole tablets taken over five to seven days are recommended, as they are considered to be the most effective treatment. These can be taken if you have symptoms of BV while you are pregnant.
If you are breastfeeding, metronidazole gel is usually recommended as the tablets can affect your breast milk.
Occasionally an alternative antibiotic may be recommended instead of metronidazole, such as clindamycin cream applied to the inside of the vagina once a day for seven days. This cream may be prescribed if you have had a reaction to metronidazole in the past, for example.

Whichever course of antibiotics you are prescribed, it is important to finish the course, even if you have started to feel better. This will help reduce the risk of symptoms persisting or recurring.

Side effects

Metronidazole can cause nausea, vomiting and a slight metallic taste in your mouth. It is best to take it after eating food. Contact your doctor if you start vomiting when you take the drug. They may recommend trying an alternative form of treatment.
Do not drink alcohol while taking metronidazole and for at least 48 hours after finishing the course of antibiotics. Drinking alcohol while taking this medicine can cause more severe side effects.

Further treatment

In some women, the first course of treatment does not effectively treat BV.
If your initial treatment has been unsuccessful, your doctor will need to check that you took the medicine correctly. If you did, you may be prescribed one of the different options described above.
If you have an intrauterine device (IUD) that your doctor thinks may be contributing to your BV, they may recommend having it removed and using an alternative form of contraception.

Vaginal pH correction treatments

Vaginal pH correction treatments are a relatively new way of treating BV. These usually involve applying a gel to the inside of your vagina that changes the acid balance, making it a less hospitable environment for harmful bacteria. Most vaginal pH correction treatments are available over the counter from pharmacists.
However, it is not clear how effective these treatments are for treating the condition. Some studies have suggested they may help treat BV, whereas others suggest they are either ineffective or less effective than treatment with antibiotics.

Referral to a specialist

If you have repeated episodes of BV in a short space of time, your doctor may recommend that you are referred to a genitourinary medicine (GUM) specialist for further investigation and treatment.
If you are pregnant, you may be referred to your midwife or obstetrician (a specialist in pregnancies). They will be able to discuss treatment options with you.


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.

Can I pass it on to my partner?

There’s no evidence that the bacteria causing bacterial vaginosis (BV) will affect male sexual partners.
However, some evidence suggests that women with BV may be able to pass the condition on to female sexual partners.

Things to avoid during treatment

While you are being treated for bacterial vaginosis (BV), there are some things you should avoid to reduce the chances of treatment being unsuccessful.
For example, you should avoid cleaning the inside of your vagina (douching) or using antiseptics, scented soaps and bubble baths in the bath.