(Date: May 2020. 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?

Colestyramine/cholestyramine (Questran®) is a medicine used to treat a number of conditions including high cholesterol, certain types of diarrhoea, a rare liver condition called primary biliary cirrhosis, and blockage of the bile ducts.

Colestyramine is also given to women who have taken a medicine called leflunomide and who are planning a pregnancy or have an unplanned pregnancy within two years of their last dose. Leflunomide causes severe birth defects in animals and there is therefore concern that it may cause birth defects in humans if taken in early pregnancy. Colestyramine helps to “wash out” leflunomide from the mother’s body to prevent it reaching the baby in the womb. For more general information please read the bump leaflet on leflunomide.

Colestyramine does not enter the bloodstream but stays in the digestive system before being passed out in the faeces.

Is it safe to take colestyramine in pregnancy?

When deciding whether or not to take colestyramine during pregnancy it is important to weigh up the benefits of its use against the known or possible risks, some of which will depend on how many weeks pregnant you are.

This leaflet summarises the scientific studies relating to the effects of colestyramine on a baby in the womb. It is advisable to consider this information before taking colestyramine if you are pregnant. Your doctor is the best person to help you decide what is right for you and your baby.

What if I have already taken colestyramine 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 colestyramine 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.

One very small study of 31 pregnant women exposed to colestyramine in early pregnancy did not find any link with birth defects in their babies. No further scientific studies have specifically investigated whether birth defects are more common in babies of women who are treated with colestyramine and further research is therefore required. As colestyramine does not enter the bloodstream it is unlikely that it will reach a baby in the womb and cause birth defects directly. However, colestyramine absorbs substances from the mother’s body, including certain vitamins, and it is unclear whether this could have an effect upon the baby’s development. Further research to investigate this is ideally required.

Can taking colestyramine in pregnancy cause miscarriage?

One very small study of 31 pregnant women exposed to colestyramine did not find any link with miscarriage. While this is reassuring, studies of much larger numbers of pregnant women using colestyramine are required to confirm this finding.

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

Two stillbirths have been reported in the scientific literature, among a collective total of 223 pregnancies with exposure to colestyramine. This is similar to the expected rate of stillbirth in the background population and does not raise alarm that colestyramine exposure causes stillbirth; however, more research is required to confirm this.

None of five small studies found any link between exposure to colestyramine in pregnancy and reduced growth of the baby in the womb. While some studies have shown that women exposed to colestyramine in pregnancy may be more likely to have a preterm delivery, this is thought to be due to the fact that the underlying illnesses that colestyramine is used to treat often lead to induced early delivery of the baby and not a direct effect of colestyramine itself.

Can taking colestyramine in pregnancy cause any other problems?

Colestyramine use can cause vitamin K deficiency (low vitamin K levels) because it absorbs vitamin K from the body. Vitamin K is required for blood to clot properly and low levels in pregnancy can therefore lead to bleeding problems in both the mother and the baby. Pregnant women taking colestyramine may therefore be offered additional blood tests to check their clotting and are likely to be advised to take a vitamin K supplement.

Can taking colestyramine 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.

One small study that included a total of 38 babies who were exposed to colestyramine in the womb did not show any problems with their early development. However, further studies of different aspects of learning and behaviour in older children exposed in the womb to colestyramine are ideally required.

Will I or my baby need extra monitoring during pregnancy?

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 colestyramine during pregnancy is not expected to cause any problems that would require extra monitoring of your baby.

Additional blood tests to check blood clotting may be required following exposure to colestyramine in pregnancy (see above).

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

We would not expect any increased risk to your baby if the father took colestyramine 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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