(Date: February 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?

Natalizumab is an antibody therapy used to treat multiple sclerosis (MS).

What are the benefits of using natalizumab in pregnancy?

Natalizumab reduces MS symptoms by stopping the immune system from attacking nerves.

Are there any risks of using natalizumab during pregnancy?

Use of natalizumab in pregnancy has not been well-studied. While the available information does not suggest that natalizumab harms the baby, ongoing data collection is needed to confirm that it is safe.

Natalizumab used in later pregnancy can potentially affect the baby’s immune system for up to six months after birth. Live vaccines should be avoided during this time. This means that the baby cannot be vaccinated against rotavirus (as this needs to be completed by four months) and should not receive the BCG vaccine (if required) until they are six months old.

Are there any alternatives to taking natalizumab?

Yes. Other medicines can be used to treat MS during pregnancy, although for some women these may not work as well as natalizumab.

You may find that your symptoms improve during pregnancy; if so, your specialist may advise that your medicine(s) can be altered or stopped. However, please do not change or stop your medication without speaking to your doctor.

If you are planning a pregnancy you should speak to your specialist to determine which medicine is best. This can be arranged through your GP or neurology clinic nurse.

If you become pregnant while taking natalizumab you should be reviewed by your doctor as soon as possible.

What if I prefer not to take natalizumab during pregnancy?

Your doctor will be happy to talk to you about any concerns that you might have. It is important that your MS is well-treated during pregnancy in order to avoid a flare-up of symptoms and to keep you healthy.

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 further scans to check for birth defects will be required, although you may be offered extra growth scans.

Everyone who takes natalizumab receives regular monitoring for a condition called progressive multifocal leukoencephalopathy (PML) which can be a side effect of treatment. This monitoring will continue during pregnancy as required.

Are there any risks to my baby if the father takes natalizumab?

There is currently no evidence that natalizumab 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 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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