Date: October 2022, Version 4

Quick read

It is very important to correctly treat an infection in pregnancy. Metronidazole may be recommended for some types of infection where the benefits of treatment are thought to outweigh the possible risks.

What is it?

Metronidazole (Flagyl®) is used to treat a number of infections, including skin infections, dental infections, and bacterial vaginosis. It is also used to eradicate a type of stomach bacteria called Helicobacter pylori, which can cause stomach ulcers.


What are the benefits of taking metronidazole in pregnancy?

Metronidazole treatment can reduce unpleasant symptoms and prevent serious complications from an infection, including some pregnancy problems.


Are there any risks of taking metronidazole in pregnancy?

Metronidazole use in pregnancy has been well studied and is not known to cause birth defects, stillbirth, low birth weight, or preterm delivery. Although some studies have shown that miscarriage might be more common in women taking metronidazole in early pregnancy, it is unclear if the increased risk might be caused by the infections that metronidazole was being used to treat.


Are there any alternatives to taking metronidazole in pregnancy?

Possibly, although alternative antibiotics may not work as well as metronidazole for some types of infection. A doctor or midwife will be able to discuss why a particular antibiotic is advised as the best treatment.

No treatment

What if I prefer not to take medicines in pregnancy?

It is important that an infection in pregnancy is well-treated as it can lead to very unpleasant symptoms, as well as serious complications for both mother and baby.

A doctor will only prescribe medicines when necessary and will be happy to talk about any concerns.

Will I or my baby need extra monitoring?

As part of routine antenatal care in the UK, women are invited for a very detailed scan at around 20 weeks of pregnancy to check the baby’s development. No further monitoring is required for women taking metronidazole.

Are there any risks to my baby if the father has used metronidazole?

There is no evidence that metronidazole used by the father can harm the baby through effects on the sperm.

Who can I talk to if I have questions?

If you have any questions regarding the information in this leaflet, please discuss them with your health care provider. They can access more detailed medical and scientific information from

How can I help to improve drug safety information for pregnant women in the future?

Our online reporting system (MyBump Portal) allows women who are currently pregnant to create a secure record of their pregnancy, collected through a series of questionnaires. You will be asked to enter information about your health, whether or not you take any medicines, your pregnancy outcome and your child's development. You can update your details at any time during pregnancy or afterwards. This information will help us better understand how medicines affect the health of pregnant women and their babies. Please visit the MyBump Portal to register.

General information
Sadly, miscarriage and birth defects can occur in any pregnancy.

Miscarriage occurs in about 1 in every 5 pregnancies, and 1 in every 40 babies are born with a birth defect. This is called the ‘background risk’ and happens whether medication is taken or not.

Most medicines cross the placenta and reach the baby. For many medications this is not a problem. However, some medicines can affect a baby’s growth and development.

If you take regular medication and are planning to conceive, you should discuss whether your medicine is safe to continue with your doctor/health care team before becoming pregnant. If you have an unplanned pregnancy while taking a medicine, you should tell your doctor as soon as possible.

If a new medicine is suggested for you during pregnancy, please make sure that the person prescribing it knows that you are pregnant. If you have any concerns about a medicine, you can check with your doctor, midwife or pharmacist.

Our Bumps information leaflets provide information about the effects of medicines in pregnancy so that you can decide, together with your healthcare provider, what is best for you and your baby.