(Date: January 2019. 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?

Baclofen (Lyflex®, Lioresal®) is a medicine used to treat severe muscle tightness and muscle spasms that may be caused by multiple sclerosis, cerebral palsy, stroke, head injury, or meningitis. Baclofen can be given by mouth, or injected intrathecally (into the fluid-filled space around the spinal cord), sometimes continuously via a pump that is implanted under the skin.

Is it safe to use baclofen in pregnancy?

When deciding whether or not to use baclofen during pregnancy it is important to weigh up how necessary baclofen 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. Remaining well is particularly important during pregnancy and whilst caring for a baby. For some pregnant women treatment with baclofen may be considered necessary.

This leaflet summarises the scientific studies relating to the effects of baclofen on a baby in the womb. It is advisable to consider this information if you are taking baclofen and are pregnant or could become pregnant in the future.

Your doctor is the best person to help you decide what is right for you and your baby.

What if I have already used baclofen during pregnancy?

If you have taken or are taking 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, if so, to make sure that you are taking the lowest dose that works and only for as long as you need to.

It is very important that you do not suddenly stop using baclofen as this could be dangerous to you, and also to your baby if you are already pregnant. Do not make any changes to your medication without first talking to your doctor.

Can using baclofen in pregnancy cause birth defects in the baby?

 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.

A single study reported the pregnancy outcomes of 134 women taking baclofen during the first trimester. There is currently no proof that use of baclofen in early pregnancy causes birth defects. However, because such a small number of pregnancies have been studied, more information on this subject needs to be collected to confirm this.

Can using baclofen in pregnancy cause miscarriage?

A single study investigated the chance of miscarriage in 134 women taking baclofen during the first trimester. No link with miscarriage was observed. However, because such a small number of pregnancies have been studied, more information on this subject needs to be collected to confirm this.

Can using baclofen in pregnancy cause preterm birth, my baby to be small at birth (low birth weight), or stillbirth?

No scientific studies have investigated whether there may be links between using baclofen during pregnancy and having a premature baby (born before 37 weeks of pregnancy), a low birth weight baby (weighing less than 2,500g), or a stillbirth. More research is needed before we can be sure that baclofen use in pregnancy does not increase the likelihood of these events.

Can using baclofen in pregnancy cause other health problems in the child?

Withdrawal symptoms at birth (neonatal withdrawal)
Withdrawal symptoms are thought to occur when a newborn baby’s body has to adapt to no longer getting certain types of medicines through the placenta.

Baclofen works in a similar way to other medicines that are known to cause neonatal withdrawal. There are a number of reports of withdrawal symptoms in babies whose mothers took baclofen by mouth around the time of delivery. Close monitoring of your baby for a few days after birth may, therefore, be advised if you have taken baclofen regularly in the weeks before delivery. Babies of women who receive intrathecal (i.e. injected into the spine) baclofen during pregnancy are not thought to be at high risk of neonatal withdrawal, as baclofen given this way enters the mother’s (and therefore the baby’s) bloodstream in much smaller amounts than baclofen taken by mouth.

Learning and behavioural problems
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.

No large studies have been carried out to investigate whether exposure to baclofen in the womb can cause problems with a child’s learning or behaviour. There are isolated reports of seven children whose mothers received baclofen in pregnancy (two by mouth, five intrathecally). All of these children were developing normally up to the age of 2 years. However, development needs to be studied in many more children of different ages before we can say whether baclofen use in pregnancy can cause changes in learning and behaviour.

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.

Taking baclofen in pregnancy is not known to cause problems that would require extra monitoring of your baby, but because there is very little information on the use of baclofen in early pregnancy, if you have taken baclofen in the first trimester your doctor may suggest an earlier and/or more detailed scan.

Women with some of the illnesses that baclofen is used to treat may be more closely monitored during pregnancy to ensure that they remain well throughout and that their baby is growing and developing as expected.

If you have taken baclofen by mouth around the time of delivery your baby may require extra monitoring after birth because of the risk of neonatal withdrawal.

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

We would not expect any increased risk to your baby if the father used baclofen 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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