best use of medicines in pregnancy

Imatinib

(Date: August 2015. Version: 1a)

What is it?

Imatinib (Glivec^®) is a type of medicine called a tyrosine kinase inhibitor. It works by blocking the activity of molecules that are important for the growth and division of certain cell types. Imatinib is used to treat certain types of leukaemia, tumours of the digestive tract, and other cancers.

Is it safe to take imatinib in pregnancy?

There is no yes or no answer to this question. When deciding whether to take imatinib during pregnancy it is important to weigh up how necessary imatinib is to your health against any possible risks to you or your baby, some of which may depend on how many weeks pregnant you are. Use of imatinib in pregnancy may sometimes be considered necessary to keep leukaemia or another type of cancer under control for the benefit of both the mother and her unborn baby. Your doctor is the best person to help you decide what is right for you and your baby.

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

What if I have already taken imatinib during pregnancy?

If you have taken 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 to make sure that you are taking the lowest dose that works.

Can taking imatinib 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.

No high quality studies have specifically analysed whether birth defects are more common in babies of pregnant women taking imatinib. There are 119 single reports in medical publications of babies whose mothers took imatinib during the first trimester of pregnancy. Birth defects were reported in 14 of these babies, of which four babies displayed similar birth defects in various combinations. These included exomphalos (where some of the baby’s bowel and liver protrudes outside of his/her body through a weakness in the muscle surrounding the tummy button), renal agenesis (where one or both kidneys are missing), hemivertebrae (a defect of the spine bones), and/or scoliosis (curvature of the spine that may occur because the spine bones are abnormal).

The fact that several babies with an unusual combination of birth defects have been reported raises the possibility that these birth defects may have been caused by imatinib. However, the majority of babies exposed in the first trimester to imatinib did not have these birth defects. It is also not uncommon for an unusual case to be written up more than once and these reports may therefore all relate to only one or two babies. Also, genetic mutations (‘spelling errors’ in a person’s genes) can cause a similar pattern of birth defects, and were not tested for in these children to rule this out as a cause. More research is therefore required to determine whether exposure to imatinib in early pregnancy can cause birth defects in the baby, and if so what the chances are of a baby being affected.

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

No studies have specifically assessed the rates of these pregnancy outcomes in pregnant women taking imatinib. Studies are therefore required to determine whether use of imatinib in pregnancy affects the chance of miscarriage, stillbirth, preterm birth, or low birth weight in the baby.

Can taking imatinib in pregnancy cause learning and 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 been carried out to investigate whether children exposed in the womb to imatinib are more likely to develop learning and behavioural problems, e.g. autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD). There are case reports of 22 babies and children exposed to imatinib in the womb who were said to be developing normally. There has also been a report of a four year old (born with malformations) with delayed development and learning disorders following exposure to imatinib in the womb. Large scale studies of the effects of imatinib exposure in pregnancy on learning and behaviour in the child are required.

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. Because the effects of taking imatinib in pregnancy are unknown your doctor may suggest extra monitoring of your baby, including more detailed scans for birth defects and monitoring of your baby’s growth in the womb. Women with the illnesses that imatinib 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.

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

There are a number of studies in which a small a group of pregnancies fathered by men who took imatinib around the time of conception are followed up. There is no indication that adverse outcomes are more likely in these pregnancies. Most experts agree that the majority of medicines used by the father are unlikely to harm the baby through affects on the sperm. However, more research on the effects of imatinib specifically, and medicine use in men around the time of conception generally, is needed.

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.

   

www.medicinesinpregnancy.org

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.