(Date: June 2017. Version: 3.1)

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 used to treat infections of the bladder (also called lower urinary tract infections or UTIs).

Is it safe to use nitrofurantoin in pregnancy?

The timely and correct treatment of bladder infections during pregnancy may be crucial to the health of both mother and baby. Untreated, bladder infections can lead to infections of the kidneys (pyelonephritis), which can be dangerous for the mother and have also been linked to preterm labour.

When deciding whether or not to take nitrofurantoin during pregnancy it is important to weigh up how necessary this is to your health against the possible risks to you or your baby, some of which will depend on how many weeks pregnant you are. Your doctor is the best person to help you decide what is right for you and your baby.

What if I have already taken nitrofurantoin during pregnancy?

Nitrofurantoin is commonly prescribed in pregnancy with no known adverse effects on the developing baby. However, it is always a good idea to let your doctor know that you are pregnant if you have taken any medicines in case you need any additional monitoring or treatment.

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

You should not alter the dose of any of your medicines without medical supervision. Your doctor is the best person to help you decide what is right for you and your baby.

Can taking nitrofurantoin antibiotic 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.

One study of over 9,000 babies born to women who took nitrofurantoin in early pregnancy found that birth defects were no more common in their babies than in babies of women not taking nitrofurantoin. Although the only other study to investigate this found that babies exposed to nitrofurantoin were at slightly increased risk of birth defects, problems with the way that the data was collected mean that this result may not be reliable.

A number of studies have investigated whether nitrofurantoin use in pregnancy might increase the likelihood of specific types of birth defect in the baby. There is currently no convincing evidence from these studies that this is the case.

Can taking nitrofurantoin in pregnancy cause miscarriage?

One large study found no link between use of nitrofurantoin in early pregnancy and miscarriage. Ideally, further studies are required to confirm this finding.

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 stillbirth, preterm birth, or my baby to be small at birth (low birth weight)?

One large study found that pregnant women taking nitrofurantoin were not at increased chance of having a stillbirth, a preterm birth, or a baby with a low birth weight compared to women not taking nitrofurantoin. Because only one study has investigated these pregnancy outcomes in women taking nitrofurantoin, more research is required to confirm these findings.

Can taking nitrofurantoin in pregnancy cause learning or 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.

One study provided no convincing proof that exposure to nitrofurantoin in the womb causes cerebral palsy in the baby, although there was evidence to support that serious infections in the mother during pregnancy can increase the risk of cerebral palsy in the baby.

Further research into other aspects of learning and development in children exposed in the womb to nitrofurantoin is required.

Will my baby need extra monitoring?

As part of their routine antenatal care most women will be offered a scan at around 20 weeks of pregnancy to look for birth defects and to check the baby’s growth.

There is no evidence that taking nitrofurantoin during pregnancy causes any problems that would require extra monitoring of your baby. 

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

We would not expect any increased risk to your baby if the father took nitrofurantoin before or around the time you became pregnant.

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  

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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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