(Date: May 2022. 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?

Allopurinol is taken in combination with other medicines to treat inflammatory bowel disease. It is also used to help prevent rejection of a transplanted organ and to treat gout, kidney stones, and high levels of uric acid in the blood that can occur due to chemotherapy.

What are the benefits of taking allopurinol in pregnancy?

Allopurinol is sometimes used during pregnancy to help control inflammatory bowel disease, which is very important both for the woman’s wellbeing and to prevent certain pregnancy complications. It is also vital for both mother and baby that a transplanted organ continues to function well during pregnancy, and that the symptoms of painful conditions such as gout and kidney stones are well-controlled.

What are the risks of using allopurinol in pregnancy?

Only a small number of pregnant women taking allopurinol have been studied. The majority of the available information does not raise concern that its use causes problems. However, two babies exposed in the womb to allopurinol were born with similar, unusual birth defects. Ongoing research is therefore required to rule out that, in rare cases, allopurinol use can cause problems.

Are there any alternatives to using allopurinol in pregnancy?

Possibly. Other medicines are available to treat the illnesses that allopurinol is used for. However, if allopurinol was working well before pregnancy, a woman may be advised by her doctor to continue taking it. This will benefit both her and her baby by ensuring that her condition remains well-controlled.

Women who accidentally conceive while taking allopurinol should arrange to see their doctor or specialist to ensure that allopurinol is still the best treatment and to make sure the dose is correct.

What if I prefer not to take medicines during pregnancy?

It is very important that inflammatory bowel disease is controlled, and that organ rejection continues to be prevented during pregnancy. Your doctor will only prescribe medicines when absolutely necessary and will be happy to talk to you about any concerns that you might have.

Will I or my baby need any extra monitoring?

As part of routine antenatal care, most women will be offered a very detailed scan at around 20 weeks of pregnancy to check the baby’s development. No additional monitoring is required due to taking allopurinol in pregnancy, although women with inflammatory bowel disease and organ transplants are likely to be offered additional monitoring of their own and their baby’s wellbeing.

Are there any risks to my baby if the father has used allopurinol?

There is no evidence that allopurinol used by the father can harm the baby through effects on the sperm..

Who can I talk to if I have questions?

If you have any questions about the information in this leaflet, please discuss them with your health care provider. They can access more detailed medical and scientific information from

How can I help to improve drug safety information for pregnant women in the future?

Our online reporting system allows women with a current or previous pregnancy to create a digitally secure ‘my bumps record’. You will be asked to enter information about your health, whether or not you take any medicines, and your pregnancy outcome. You can update your details at any time during pregnancy or afterwards. This information will help us better understand how medicines affect the health of pregnant women and their babies. Please visit to register.

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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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