(Date: April 2021. Version: 2)

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?

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.

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

Feedback request 

WE NEED YOUR HELP! Do you have 3 minutes to complete a short, quick and simple 12 question user feedback form about our bumps information leaflets? To have your say on how we can improve our website and the information we provide please visit here.

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.

My bump’s record

Create your own ‘My bump’s record’.

Provide information about your pregnancy to help women in the future.

Login to my bumps

Join my bumps