(Date: December 2013. Version: 2)

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.

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What is it?

Leflunomide is a medicine used to treat rheumatoid arthritis, and a type of arthritis that sometimes affects people with the skin condition psoriasis (psoriatic arthritis).

Is it safe to take leflunomide in pregnancy?

Taking leflunomide before or during pregnancy may harm an unborn baby (see below).

Leflunomide stays in the body for more than a year after a person has stopped taking it. For this reason, it is recommended that women should wait for two years after stopping treatment with leflunomide before attempting to become pregnant.

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. Depending on how many weeks pregnant you are you may be offered a second medicine called colestyramine that helps clear leflunomide from the body.

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

There is very little information from studies of human pregnancies about whether leflunomide is safe to use. Animal studies have shown 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.

A small number of studies have looked at whether women who took leflunomide during pregnancy or within two years of conceiving were more likely to have a baby with a birth defect. Most of the women in these studies had been treated with colestyramine to clear the leflunomide from the body as soon as they realised they were pregnant. It is therefore not possible to use this information to say whether leflunomide itself causes birth defects in humans. However, these studies suggest that if a women who has taken leflunomide receives treatment with colestyramine early enough in pregnancy she is at no greater risk than any other woman in the general population of having a baby with a birth defect.

While this is reassuring, because only a very small number of women taking leflunomide have been studied so far, we do not know yet whether colestyramine is always an effective treatment, or how early in pregnancy it has to be used to prevent leflunomide possibly affecting an unborn baby.

Can taking leflunomide in pregnancy cause miscarriage?

There is mixed evidence about whether taking leflunomide before or during pregnancy increases the chance of miscarriage. Miscarriage risk has been studied in only a few small groups of women. While some studies have shown a link between taking leflunomide and having a miscarriage, others have not. More information is needed before firm conclusions can be drawn.

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

Two studies have shown that women taking leflunomide during pregnancy may be more likely to have a premature baby (born before 37 weeks of pregnancy). Women who had taken leflunomide within two years of conceiving also seemed to be more likely to give birth earlier, but the chance of this was not as high as for women who had taken leflunomide during pregnancy.

The same two studies also showed that babies born to women taking leflunomide during pregnancy were generally smaller than babies born to women not taking leflunomide.

However, it is not possible to say whether premature delivery and low birth weight is caused by leflunomide, or by other factors such as the illnesses for which women may be taking leflunomide. More research is required before any firm conclusions can be drawn.

Can taking leflunomide in pregnancy cause stillbirth?

No link between leflunomide use in pregnancy and having a stillbirth is known about, however no scientific studies have been carried out that have specifically investigated this.

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.

There is no known link between taking leflunomide in pregnancy and learning or behavioural problems such as attention deficit hyperactivity disorder (ADHD) or autism spectrum disorder (ASD). There are, however, no scientific studies that have specifically investigated a link with these problems.

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 undergo treatment with colestyramine to help clear leflunomide from their body.

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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WE NEED YOUR HELP! Do you have 3 minutes to complete a short, quick and simple 12 question user feedback form about our bumps information leaflets? To have your say on how we can improve our website and the information we provide please visit www.surveymonkey.co.uk/r/uktis-bumps.

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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