(Date: October 2018. 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 the UK Health Security Agency (UKHSA) 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?

Leflunomide is a medicine used to treat inflammatory arthritis (such as rheumatoid and psoriatic arthritis).

Is it safe to take leflunomide in pregnancy?

Animal studies have suggested that leflunomide can cause birth defects. Although results from animal studies cannot always be directly applied to humans, until more detailed information about women who have taken leflunomide is collected and studied, we have to assume that leflunomide may not be safe to use during pregnancy. For this reason, women taking leflunomide are generally advised not to become pregnant.

Leflunomide stays in the body for more than a year after a person has stopped taking it. It is therefore recommended that women should wait for two years after stopping treatment with leflunomide before attempting to become pregnant. If you become pregnant or are planning a pregnancy and have been on leflunomide in the last two years then you should see your doctor as soon as possible as you may need treatment to ‘washout’ the leflunomide from your body.

What if I have already taken leflunomide during pregnancy?

If you become pregnant whilst taking leflunomide, or within two years of stopping it, you should consult your doctor as soon as possible. They will be able to advise you on switching medicines to control your arthritis and may also offer leflunomide ‘washout’ treatment.

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

Women who become pregnant while taking leflunomide, or who conceive within two years of stopping treatment, do not seem to have a higher chance of having a baby with a birth defect than women not taking leflunomide, provided that leflunomide is stopped when pregnancy is recognised and washout treatment is given. Only a relatively small number of pregnancies exposed to leflunomide have been studied (around 450) and more information therefore needs to be collected.

Can taking leflunomide in pregnancy cause miscarriage?

Exposure to leflunomide in early pregnancy does not seem to increase the chance of miscarriage. However, further research is required to confirm this as data is limited.

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

It is difficult to assess the effect of leflunomide on pre-term birth and low birth weight because inflammatory arthritis has an effect on pregnancy.

One small study showed that taking leflunomide in the second and third trimesters was not linked to preterm birth or low birth weight in the baby. However, a separate small study found that women taking leflunomide during pregnancy were more likely to have a premature baby or to have a baby with a lower than average birth weight. More research is therefore required before any firm conclusions can be drawn.

Can taking leflunomide in pregnancy cause stillbirth?

No studies have been carried out that have specifically investigated the chance of stillbirth in pregnancies exposed to leflunomide.

Can taking leflunomide 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.

No studies have investigated learning and behaviour in children exposed in the womb to leflunomide.

Will my baby need extra monitoring?

If you have become pregnant whilst taking, or within two years of taking, leflunomide, even if you have been treated with colestyramine, your obstetrician may offer you a detailed fetal ultrasound scan to check for birth defects in your baby.

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

It is unlikely that there would be an increased risk to your baby if the father took leflunomide before or at around the time you became pregnant. However, it is recommended that men who have used leflunomide within the last two years and who are planning a pregnancy with their partner should seek advice from their rheumatologist with regards to stopping the drug and/or washout prior to trying to conceive.

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 www.uktis.org.  

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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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