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Always tell your doctor if you have vaginal bleeding when you are pregnant

Bacterial vaginosis in pregnancy: What you need to know

Your body goes through a whole host of changes when you’re pregnant - and not all of them are welcome. Bacterial vaginosis, a vaginal infection caused by an imbalance of bacteria in the vagina, can be common when you’re expecting a baby1. Although it's not normally dangerous, it has been linked to pregnancy complications. So here's what you need to know about it.

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What is bacterial vaginosis?

Our bodies contain an array of good bacteria that help keep us healthy. The vagina is colonised by bacteria called lactobacilli which help to keep everything in check and prevent harmful pathogens from getting inside.

Sometimes, however, the balance of these bacteria can change - and bacteria other than lactobacilli can overgrow in the vagina, causing symptoms like unusual discharge. This is called bacterial vaginosis or BV.

Bacterial vaginosis is the most common vaginal infection in women between the ages of 15 to 442. It's common among pregnant women, possibly because of the hormonal changes that take place.

Dr Krishna Vakharia, a GP and clinical director of, says: “Bacterial vaginosis doesn't usually cause problems during pregnancy, but there is a link between BV and some pregnancy complications.”

Research shows that bacterial vaginosis can lead to premature labour and birth if left untreated3. It has also been linked to low birthweight, a problem associated with an increased risk of infant mortality, developmental problems in childhood, and poorer health in later life4. Therefore, it's important to get checked out and treated if you notice any changes to your vagina during pregnancy.

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What are the symptoms of bacterial vaginosis?

Often, there are no symptoms of bacterial vaginosis. Some women may notice a change in the normal secretions from the vagina.

"This discharge will usually be white or grey, thin or watery and have a strong, unpleasant fishy smell. You may also experience itching, burning, or irritation in the vaginal area," says Vakharia.

It can be challenging to differentiate between normal changes in vaginal discharge during pregnancy and bacterial vaginosis. When you’re pregnant, it’s normal to have more discharge than you normally would. This helps to prevent any infections from travelling up the vagina and into the womb, protecting the foetus5. However, there are some key differences.

"Normal pregnancy discharge is usually thin, white, and odourless or has a mild, slightly sweet smell. It should not be accompanied by itching, burning, or unusual discomfort," says Vakharia.

Symptoms of Bacterial vaginosis

A thin white or grey discharge.

A strong, fishy smell.

Itching or irritation in your genital area.

Burning when you urinate.

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What to do if you think you have bacterial vaginosis in pregnancy

If you think you have bacterial vaginosis you should make an appointment with your GP. Make sure you tell the doctor or nurse if you are pregnant, think you might be pregnant, or are breastfeeding.

More often than not, doctors will diagnose and treat based on the symtpoms. Rarely, if the diagnosis is not clear, the doctor may carry out an examination to check your vagina and use a swab to collect a sample to test. This only takes a couple of minutes and may be slightly uncomfortable, but isn’t normally painful. Sometimes, a diagnosis can be made straight away using a piece of paper that changes colour depending on the pH - alkaline/acid balance - of your vagina.

Treatment for bacterial vaginosis

Bacterial vaginosis is treated with antibiotics. An antibiotic cream or gel to use in the vagina may be given instead of antibiotic tablets by mouth.

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Further reading

  1. Chee et al: Vaginal microbiota and the potential of Lactobacillus derivatives in maintaining vaginal health.

  2. March of Dimes: Bacterial vaginosis and pregnancy.

  3. Shimaoka et al: Association between preterm delivery and bacterial vaginosis with or without treatment.

  4. Hillier et al: Association between bacterial vaginosis and preterm delivery of a low-birth-weight infant.

  5. Tommy’s: Discharge in pregnancy.

Article history

The information on this page is peer reviewed by qualified clinicians.

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