Bacterial vaginosis

Bacterial vaginosis is a condition that is caused by an imbalance in the natural bacteria in the vagina. It is a common cause of abnormal vaginal discharge.

Symptoms of bacterial vaginosis

Often there are no symptoms associated with bacterial vaginosis.

When symptoms do occur, they most commonly include:

  • a thin vaginal discharge that is white or grey; and
  • discharge that has an unpleasant odour (often described as a strong fishy odour, especially noticeable after intercourse).

Other symptoms include:

  • vaginal discomfort (itching or irritation);
  • pain during intercourse; and
  • burning during urination.


The exact cause of bacterial vaginosis is not known. The problem is thought to be due to an imbalance in the types of bacteria that are normally found in the vagina – an overgrowth of ‘bad’ bacteria (anaerobic bacteria) and not enough ‘good’ bacteria (lactobacilli).

Risk factors

It is thought that sexual activity with a new sexual partner or multiple partners can increase your risk of bacterial vaginosis. Having a female sex partner may also increase the risk of bacterial vaginosis. However, it is possible to have bacterial vaginosis if you are not sexually active.

Frequent douching (using a cleanser or water to clean inside the vagina) and having an IUD (intra-uterine device) are other factors that can increase your chances of getting bacterial vaginosis.


A vaginal swab can be taken to test the vaginal discharge.

The sample is examined under a microscope to look for:

  • ‘clue cells’ — vaginal cells covered with bacteria that are a diagnostic sign of bacterial vaginosis; and
  • an overgrowth of anaerobic bacteria.

Testing the acidity of the vagina also helps with diagnosis – a pH higher than 4.5 makes a diagnosis of bacterial vaginosis more likely.

Bacterial vaginosis treatment

Your doctor may prescribe antibiotics such as metronidazole or clindamycin for bacterial vaginosis. Either an antibiotic vaginal cream or gel, or oral antibiotics (tablets) can be used.

Treating male sex partners is not usually required, but spread between female sex partners is possible.

Unfortunately, recurrence of symptoms is common, usually within 3 to 6 months of treatment.

Complications associated with bacterial vaginosis

It’s important to treat bacterial vaginosis because it can be associated with other problems.

  • Women with bacterial vaginosis who have a hysterectomy or dilation and curettage (D and C) have a higher risk of infection following surgery.
  • Pregnant women with bacterial vaginosis are at risk of premature delivery and having a baby with a low birth weight.
  • You are more susceptible to sexually transmitted infections (STIs) if you have bacterial vaginosis.


Avoid douching — douching is not necessary as the vagina is self-cleaning. Douching can actually increase your chances of getting a vaginal infection.

See your doctor if you are concerned about an unpleasant vaginal discharge or vaginal discomfort. You may need treatment for bacterial vaginosis.

Last Reviewed: 25 January 2012


1. Bacterial vaginosis (revised June 2010). In: eTG complete. Melbourne: Therapeutic Guidelines Limited; 2011 Nov. (accessed Jan 2012).
2. Mayo Bacterial vaginosis (last updated 15 Sep 2010). (accessed Jan 2012).
3. Centers for Disease Control and Prevention. Bacterial vaginosis – CDC fact sheet (updated 28 April 2010). (accessed Jan 2012).


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