(Date: February 2015. Version: 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.

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What is it?

Thalidomide is a medicine that first became available in the 1950s to treat sleeping problems, and to reduce symptoms of morning sickness in pregnant women. It was banned from sale in the early 1960s as it caused birth defects in around 10,000 babies of women who had taken it during early pregnancy. However, more recently, thalidomide is being used again to treat a type of cancer of the blood called multiple myeloma, and in some countries to treat certain effects of leprosy.

Is it safe to take thalidomide in pregnancy?

No. Thalidomide use in early pregnancy, particularly around 5-7 weeks after the last period, causes severe birth defects in up to half of unborn babies who are exposed in the womb. Birth defects can be caused by a single dose of thalidomide.

Pre-menopausal women and girls who need to take thalidomide to treat a serious medical condition are required to be in a ‘Pregnancy Prevention Programme’ (PPP). This means:

• agreeing to use 2 forms of reliable contraception or to abstain from sexual intercourse during treatment, and for one month afterwards

• having a negative pregnancy test one month before starting treatment, and then having repeat pregnancy tests every month during treatment, and one month after treatment stops

• signing a consent form to say that your doctor has explained the risks to a pregnancy of thalidomide treatment and that you understand these risks

Because thalidomide stays in the body for some time after you stop taking it, it is important to avoid getting pregnant for at least one month after the last dose.

What if I have already taken thalidomide during pregnancy?

If you are pregnant or think you may be pregnant and are taking thalidomide, you should speak to your doctor as a matter of urgency. He/she will then be able to advise you what you need to do next and make sure that you are aware of the choices available to you.

What type of birth defects are caused by taking thalidomide in pregnancy?

A large number of different birth defects have been reported in children of women who took thalidomide in pregnancy. Abnormalities of the hands and arms are the most common birth defects caused by thalidomide and include a very specific abnormality termed phocomelia However, thalidomide is not the only cause of phocomelia. Spelling errors (mutations) in a person’s genes can also cause phocomelia and it is therefore possible that phocomelia in some people was not caused by thalidomide exposure.

The following birth defects have been linked to thalidomide:

• reduced/missing arms (and/or legs, but this is rarer)
• missing thumbs, or thumbs with an extra bone (triphalangism)
• club feet
• extra toes
• reduced or missing ears and deafness
• paralysis of facial nerves
• abnormally small eyes and other eye malformations

Some children of mothers who took thalidomide have just one of these birth defects and some have several. The types and number of birth defects that a baby has tends to be linked to the exact time in the pregnancy that the thalidomide was taken, and how many times during the pregnancy thalidomide was used, although birth defects have been reported in babies whose mothers took only a single dose of thalidomide during pregnancy.

A number of other birth defects including defects of the internal organs including heart, kidneys, brain, digestive, and reproductive systems have been linked to thalidomide exposure. However, it is not yet certain whether thalidomide exposure in the womb caused all of these birth defects, or whether some occurred for another reason (e.g. genetic mutations), especially in individuals without any of the other birth defects that have been strongly linked to thalidomide.

Can taking thalidomide in pregnancy cause miscarriage or stillbirth?

Thalidomide taken in pregnancy has been linked to both miscarriage and stillbirth. Some of the babies who died during pregnancy had severe birth defects. It is several decades since large numbers of pregnant women took thalidomide, and at that time, the exact numbers of women who experienced a miscarriage or stillbirth was not recorded. We therefore do not know what the chance is of a woman who has taken thalidomide during pregnancy having a miscarriage or stillbirth.

Can taking thalidomide 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.

A very small study suggested that children with structural malformations caused by thalidomide exposure in early pregnancy were at increased risk of learning problems and autism spectrum disorder (ASD). No other studies have investigated this, so this finding has not been confirmed. It is currently unknown whether children who are exposed to thalidomide in early pregnancy who are born without structural malformations may be at increased risk of learning and behavioural problems, or whether thalidomide taken after the first trimester of pregnancy might also increase the risk of problems with learning and behaviour.

Will my baby need extra monitoring during pregnancy?

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.

Women who have taken thalidomide in the month before pregnancy or during the first trimester and who decide to continue with their pregnancy, should be offered more detailed anomaly scans from as early as around 12 weeks of pregnancy. It is, however, harder to see birth defects at this stage of pregnancy, which is why the main scan for birth defects is generally offered at around 20 weeks of pregnancy. It is important to understand that scans are not able to pick up all birth defects and cannot predict whether a baby will have problems with learning.

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

When a man takes thalidomide, small amounts enter his semen (sperm). Men taking thalidomide are therefore advised to use condoms during sexual contact with pregnant women or women of childbearing potential because of the possibility that thalidomide present in semen may pose a risk to a developing baby.

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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