Also called

  • BV


  • Bacterial vaginosis can cause a watery, white or grey vaginal discharge with a strong smell.
  • Bacterial vaginosis may develop soon after sex with a new partner.
  • An antibiotic known as metronidazole is used to treat the infection.

About bacterial vaginosis

Bacterial vaginosis (BV) is caused by an imbalance of the bacteria normally present in the vagina. In women with BV, the normal healthy bacteria (in particular, lactobacilli) are replaced by an overgrowth of other mixed bacteria. The exact cause of BV is unknown.

Symptoms of BV

Symptoms of BV may include: 

  • watery, white or grey discharge from the vagina
  • a strong or unusual odour from the vagina, often described as a ‘fishy smell’.

Bacterial vaginosis may occur at the same time as sexually transmissible infections (STIs).

How BV is spread

Although it is not clear how BV is transmitted, it is more common in women who are sexually active. It sometimes develops soon after intercourse with a new partner. Women who have female sexual partners may be at higher risk than women who have sex with only male partners. 

Research has not conclusively found a link between BV and specific sexual practices or acts. However, recent evidence supports the use of condoms to reduce the risk of this infection.

Diagnosis of BV

Diagnosis is made based on signs and symptoms and lab tests. During a medical examination, your doctor may notice: 

  • copious vaginal discharge
  • odour from the vagina
  • decreased acidity of the vaginal fluid on pH testing.

Treatment for BV

If you have no symptoms, treatment is usually not required as this condition is self-limiting (will go away by itself).

Seek treatment if: 

  • you are about to have a medical procedure that could allow bacteria into the uterus – for example, insertion of an IUD, or termination of pregnancy
  • you are pregnant – BV can cause early onset of labour. Talk to your GP, obstetrician or midwife about treatment for BV if you are pregnant
  • the symptoms of BV are affecting your quality of life and you are avoiding sex because of it.

Antibiotics are used to treat BV

An antibiotic called metronidazole can be used to treat the infection. If your doctor prescribes metronidazole you will need to: 

  • Take the antibiotic twice a day for seven days. 
  • Take the tablets after meals – this can reduce the nausea and upset stomach that is sometimes associated with metronidazole.
  • Avoid drinking alcohol during treatment.

Your doctor can prescribe a vaginal cream (such as clindamycin) if you are unable to take metronidazole. Clindamycin is applied to the vagina for seven nights.

Recurrences of BV

Even after treatment, about half of the women with BV will get the condition back within six to 12 months. Treating the male partner of an infected woman does not seem to reduce the risk of recurrence, but further research is being done in this area.

Prevention of BV

Most cases of BV appear to be associated with sexual activity. Condoms have been shown to protect against infection, and safe sexual practices are recommended for all women, regardless of the gender of their partners.

Where to get help

More information

Reproductive system - female

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Fertility, pregnancy and childbirth

Content Partner

This page has been produced in consultation with and approved by: Melbourne Sexual Health Centre

Last updated: June 2020

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