Bacterial vaginosis (BV) in pregnancy: signs and treatment

Bacterial vaginosis, or BV, is one of the most common causes of unusual vaginal discharge, and one of the least talked about. It isn’t usually serious, but in pregnancy it’s worth getting treated, because there’s a small chance it can lead to complications. Treatment is simple, and in most pregnancies BV causes no problems at all.

What is BV?

BV is caused by an imbalance of the bacteria that normally live in the vagina. It isn’t a sexually transmitted infection (STI), but sex can trigger it or pass it on. The NHS advises avoiding vaginal washes, douches and perfumed products, which can upset the balance.

Signs of BV

discharge with a strong fishy smell, especially after sex
discharge that changes colour or consistency, often becoming greyish-white, thin and watery

BV doesn’t usually cause soreness or itching. Half of people with BV don’t have any symptoms at all, which is why it often goes unnoticed.

BV, thrush or trichomoniasis?

All three can change your discharge, but there are some differences:

BV: a fishy smell, with thin, watery, greyish-white discharge. Usually no itching or soreness.
Thrush: thick, white discharge like cottage cheese that doesn’t usually smell, with itching and soreness.
Trichomoniasis: a sexually transmitted infection that can cause yellow-green discharge, which may be frothy or smell fishy, along with soreness or pain. In pregnancy it can cause a baby to be born early or with a low birthweight, so it needs testing and treating, and partners need treating too.

Discharge with pelvic pain or bleeding can be a sign of chlamydia or gonorrhoea, and blisters or sores can be genital herpes. You can’t reliably tell these apart yourself, so get any change checked rather than guessing.

Why does BV matter in pregnancy?

The NHS says BV causes no problems in most pregnancies, but treatment is recommended because of the small chance of complications, such as premature birth or miscarriage. Contact your GP or midwife if your discharge changes while you’re pregnant.

BV isn’t routinely tested for in pregnancy in the UK. If you have BV but no symptoms, UK guidelines say there isn’t enough evidence to treat it routinely, but your midwife or doctor may discuss it with you if you have other risks for premature birth.

How is BV treated in pregnancy?

BV is treated with antibiotics, prescribed by a GP or sexual health clinic. Let your midwife know too. Treatments used in pregnancy include:

Metronidazole tablets, usually twice a day for 5 to 7 days. This is the usual first choice. The single large dose that’s sometimes used outside pregnancy is avoided, because the manufacturer recommends against it in pregnancy.
Metronidazole gel, put into the vagina at night for 5 nights.
Clindamycin cream, put into the vagina at night for 7 nights. It isn’t usually used in the first 3 months of pregnancy. It can weaken condoms and diaphragms during treatment and for 3 days afterwards.

If you’re breastfeeding, a gel or cream may be suggested instead of tablets, because metronidazole may change the taste of breast milk. Finish the whole course, even if your symptoms clear quickly. Male partners don’t usually need treatment, but female partners may.

When BV keeps coming back

BV often comes back, sometimes within a few months. Repeat episodes are usually treated with more antibiotics. If you get it more than 4 times in a year, you may be offered an antibiotic gel to use regularly for several months to stop it coming back. In pregnancy, your GP or sexual health clinic will advise on what’s suitable.

How to help prevent BV

Wash your genital area with water and plain soap, and have showers rather than baths if you can.
Don’t use vaginal deodorants, washes or douches.
Avoid perfumed soaps, bubble baths and antiseptic liquids in the bath.
Avoid strong detergents for washing underwear.
Don’t smoke.

Where to get checked

Your GP, midwife or a sexual health clinic can check you. Sexual health clinics often offer walk-in appointments and can usually give results faster than a GP surgery.

Questions people ask

Do I need treatment if I’m pregnant?

If you have symptoms, yes. The NHS advises getting BV treated in pregnancy because of the small chance of complications.

Is metronidazole safe in pregnancy?

Metronidazole is widely used in pregnancy. The bumps service says it isn’t known to cause birth defects, stillbirth, low birthweight or premature birth. Some studies found miscarriage may be more common after taking it in early pregnancy, but it isn’t clear whether this is caused by the medicine or the infection. UK guidelines recommend tablets twice a day for 5 to 7 days in pregnancy, rather than a single high dose. Your doctor will talk you through the options.

Did my partner give me BV?

BV isn’t classed as a sexually transmitted infection, but sex can trigger it or pass it on. It’s caused by a change in the balance of bacteria in the vagina.

Can BV affect my baby?

Most pregnancies aren’t affected. There’s a small chance of complications such as premature birth, which is why symptomatic BV is treated in pregnancy.

When to get help

Call your midwife if you have discharge that smells unpleasant, is green or yellow, makes you itchy or sore, or comes with pain when you wee. Contact your midwife or doctor straight away if you have any vaginal bleeding while you’re pregnant. If you think your waters have broken, call your maternity unit straight away.