(Date of issue: November 2015. Version: 3)

This factsheet has been written for members of the public by the UK Teratology Information Service (UKTIS). UKTIS is a not-for-profit organisation funded by Public Health England on behalf of UK Health Departments. UKTIS has been providing scientific information to health care providers since 1983 on the effects that medicines, recreational drugs and chemicals may have on the developing baby during pregnancy.

What is it?

Nitrofurantoin (Macrobid®) is an antibiotic that is used to treat and prevent urinary tract infections (UTIs), including kidney infections.

Is it safe to take nitrofurantoin in pregnancy?

Taking nitrofurantoin in pregnancy is not known to be harmful to a developing baby in the womb. However, not enough information is available yet to be able to say it is definitely safe. When deciding whether to take nitrofurantoin during pregnancy it is therefore important to weigh up how necessary nitrofurantoin is to your health against any possible risks to you or your baby, some of which might depend on how many weeks pregnant you are.

Kidney infection in pregnancy can be serious and can lead to premature labour. For some women treatment with nitrofurantoin in pregnancy to treat or prevent kidney infection might be the best option. Your doctor is the best person to help you decide what is right for you and your baby.

This leaflet summarises the scientific studies relating to the effects of nitrofurantoin on a baby in the womb. 

What if I have already taken nitrofurantoin during pregnancy?

If you have taken any medicines it is always a good idea to let your doctor know that you are pregnant so that you can decide together whether you still need the medicines that you are on and to make sure that you are taking the lowest dose that works.

Can taking nitrofurantoin in pregnancy cause my baby to be born with birth defects?

A baby’s body and most internal organs are formed during the first 12 weeks of pregnancy. It is mainly during this time that some medicines are known to cause birth defects.

Studies of over 9,000 babies born to women who took nitrofurantoin in early pregnancy have provided no strong evidence that use of nitrofurantoin increases the risk of the baby having a birth defect overall, or of any specific birth defect.

Can taking nitrofurantoin in pregnancy cause miscarriage?

No studies have assessed rates of miscarriage following use of nitrofurantoin in early pregnancy.

Can taking nitrofurantoin in pregnancy cause stillbirth?

A large study of around 6,000 pregnant women found no evidence of a link between stillbirth and use of nitrofurantoin in pregnancy.

Can taking nitrofurantoin in pregnancy cause preterm birth or my baby to be small at birth (low birth weight)?

A large study of around 6,000 pregnant women found no evidence of a link between use of nitrofurantoin in pregnancy and preterm birth or low birth weight in the baby.

Can taking nitrofurantoin in pregnancy cause learning and behavioural problems in the child?

A baby’s brain continues to develop right up until the end of pregnancy. It is therefore possible that taking certain medicines at any stage of pregnancy could have a lasting effect on a child’s learning or behaviour.

There is no known link between using nitrofurantoin in pregnancy and learning or behavioural problems (such as ADHD or autism spectrum disorder) in the child later on in life. There are, however, no scientific studies that have specifically investigated a link with these problems.

Scientific studies into the rates of behavioural and learning problems in children exposed to nitrofurantoin in the womb are required to determine whether there may be any effects.

Will my baby need extra monitoring?

Most women will be offered a scan at around 20 weeks of pregnancy to look for birth defects as part of their routine antenatal care. Taking nitrofurantoin in pregnancy is not expected to cause problems that would require extra monitoring of your baby.

Are there any risks to my baby if the father has taken nitrofurantoin?

No studies have specifically investigated whether nitrofurantoin taken by the father can harm the baby through effects on the sperm, however most experts agree that this is very unlikely. More research on the effects of medicine use in men around the time of conception is needed.

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  

General information 

Up to 1 out of every 5 pregnancies ends in a miscarriage, and 1 in 40 babies are born with a birth defect. These are referred to as the background population risks.  They describe the chance of these events happening for any pregnancy before taking factors such as the mother’s health during pregnancy, her lifestyle, medicines she takes and the genetic make up of her and the baby’s father into account.

Medicines use in pregnancy

Most medicines used by the mother will cross the placenta and reach the baby. Sometimes this may have beneficial effects for the baby.  There are, however, some medicines that can harm a baby’s normal development.  How a medicine affects a baby may depend on the stage of pregnancy when the medicine is taken. If you are on regular medication you should discuss these effects with your doctor/health care team before becoming pregnant.

If a new medicine is suggested for you during pregnancy, please ensure the doctor or health care professional treating you is aware of your pregnancy.

When deciding whether or not to use a medicine in pregnancy you need to weigh up how the medicine might improve your and/or your unborn baby’s health against any possible problems that the drug may cause. Our bumps leaflets are written to provide you with a summary of what is known about use of a specific medicine in pregnancy so that you can decide together with your health care provider what is best for you and your baby.   

Every pregnancy is unique. The decision to start, stop, continue or change a prescribed medicine before or during pregnancy should be made in consultation with your health care provider. It is very helpful if you can record all your medication taken in pregnancy in your hand held maternity records.

Disclaimer: This information is not intended to replace the individual care and advice of your health care provider. New information is continually becoming available. Whilst every effort will be made to ensure that this information is accurate and up to date at the time of publication, we cannot cover every eventuality and the information providers cannot be held responsible for any adverse outcomes following decisions made on the basis of this information. We strongly advise that printouts should NOT be kept for any length of time, or for “future reference” as they can rapidly become out of date.

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