Date: February 2022, Version 3

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.

No treatment

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

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.