Azathioprine/mercaptopurine

Date: March 2024, Version 4.0

Quick read

Azathioprine can be used in pregnancy if recommended by a specialist.

What is it?

Azathioprine (Imuran®) is used to treat severe eczema, auto-immune illnesses, such as lupus, inflammatory bowel disease, rheumatoid arthritis, and psoriasis, and to prevent the rejection of transplanted organs. Another form of the same medicine called mercaptopurine (Hanixol®, Xaluprine®), is used to treat certain forms of leukaemia, and occasionally inflammatory bowel disease.

Benefits

What are the benefits of taking azathioprine/mercaptopurine in pregnancy?

Use of azathioprine/mercaptopurine can prevent the rejection of a transplanted organ or keep leukaemia or a serious autoimmune illness under control.

Risks

Are there any risks of taking azathioprine/mercaptopurine during pregnancy?

There are no clear risks of taking azathioprine/mercaptopurine in pregnancy.

Alternatives

Are there any alternatives to taking azathioprine/mercaptopurine in pregnancy?

Possibly. There are other drugs available that work in a similar way to azathioprine/mercaptopurine. However, azathioprine/mercaptopurine has been better studied than many of the possible alternatives and is often considered to be a safer option.

No treatment

What if I prefer not to take medicines in pregnancy?

It is important to continue medicines to treat auto-immune disease and prevent transplant rejection in pregnancy to avoid serious complications for both mother and baby.

Will my baby need extra monitoring during pregnancy?

Women in the UK should be offered a very detailed scan at around 20 weeks of pregnancy as part of their routine antenatal care. Taking azathioprine/mercaptopurine in pregnancy is not expected to cause problems that would require extra monitoring of your baby. However, women with some of the illnesses that azathioprine/mercaptopurine 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.

Azathioprine/mercaptopurine treatment can cause low levels of the blood cells that fight infection and help blood clotting. If your baby shows any symptoms after birth, such as anaemia, infection, or problems with blood clotting, his/her blood count may be checked.

Are there any risks to my baby if the father has taken azathioprine/mercaptopurine?

The babies of at least 1,000 men who were using azathioprine/mercaptopurine around the time of conception have been studied and there is currently no suggestion of any link with birth defects, low infant birth weight, or preterm birth.

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.

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

Our online reporting system (MyBump Portal) allows women who are currently pregnant to create a secure record of their pregnancy, collected through a series of questionnaires. You will be asked to enter information about your health, whether or not you take any medicines, your pregnancy outcome and your child's development. 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 the MyBump Portal to register.

General information
Sadly, miscarriage and birth defects can occur in any pregnancy.

Miscarriage occurs in about 1 in every 5 pregnancies, and 1 in every 40 babies are born with a birth defect. This is called the ‘background risk’ and happens whether medication is taken or not.

Most medicines cross the placenta and reach the baby. For many medications this is not a problem. However, some medicines can affect a baby’s growth and development.

If you take regular medication and are planning to conceive, you should discuss whether your medicine is safe to continue with your doctor/health care team before becoming pregnant. If you have an unplanned pregnancy while taking a medicine, you should tell your doctor as soon as possible.

If a new medicine is suggested for you during pregnancy, please make sure that the person prescribing it knows that you are pregnant. If you have any concerns about a medicine, you can check with your doctor, midwife or pharmacist.

Our Bumps information leaflets provide information about the effects of medicines in pregnancy so that you can decide, together with your healthcare provider, what is best for you and your baby.