Date: April 2021, Version 2

What is it?

Sirolimus is a medicine that dampens the immune response. It is most commonly used following a kidney transplant to prevent the body from rejecting the new organ. It is also used to treat a rare, potentially serious lung disease called sporadic lymphangioleiomyomatosis.


What are the benefits of taking sirolimus in pregnancy?

Sirolimus reduces the risks of organ rejection following a kidney transplant and can help to slow disease progression in people with sporadic lymphangioleiomyomatosis. Both of these can be life-threatening and can lead to pregnancy complications.

Most pregnant women who take sirolimus will have started doing so before pregnancy. If so, it should be reviewed at the earliest opportunity by your specialist.


Are there any risks of taking sirolimus during pregnancy?

Very few pregnant women taking sirolimus have been studied, and while no obvious problems have been noted, further women need to be studied to rule out any ill-effects.


Are there any alternative to taking sirolimus in pregnancy?

Possibly. Women who are taking sirolimus and planning a pregnancy should speak to their doctor to discuss the possibility of switching to a different medicine. However, this may not be advisable for everyone and use of sirolimus in pregnancy may sometimes be considered necessary to prevent the rejection of a transplanted organ or to control sporadic lymphangioleiomyomatosis.

If you are already pregnant you should let your midwife, GP and/or obstetrician know that you are taking sirolimus so that it can be reviewed as soon as possible. However, do not stop taking sirolimus unless upon medical advice.

No treatment

What if I prefer not to take medicines in pregnancy?

It is very important to take any medicines prescribed to prevent organ rejection if you have received a transplant, and to reduce lung damage if you have sporadic lymphangioleiomyomatosis. These can be dangerous to the mother and can also lead to pregnancy complications.

Your doctor will only prescribe medicines when absolutely necessary and will be happy to talk to you about any concerns that you might have.

Please do not stop sirolimus without speaking to your midwife, GP or specialist.

Will my baby need extra monitoring?

All pregnant women in the UK should be offered a detailed anomaly scan at around 20 weeks of pregnancy as part of their routine antenatal care. No extra monitoring for major birth defects is required following sirolimus use in pregnancy.

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

We would not expect any increased risk to your baby if the father takes sirolimus.

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

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.