Omalizumab

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Date: June 2026, Version 1.0

Quick read

Omalizumab can be used in pregnancy if recommended by a specialist. Babies exposed during pregnancy after the first trimester might be offered some of their vaccinations later than usual.

What is it?

Omalizumab (Xolair®, Omlyclo®) is an antibody treatment that works by targeting the immune system. It is used to treat severe asthma.

Benefits

What are the benefits of using omalizumab in pregnancy?

Omalizumab treats severe asthma and is usually only used when other asthma medicines have not worked. Good asthma control in pregnancy is important, as poorly controlled asthma can increase the risk of serious complications for both you and your baby.

Risks

What are the risks of using omalizumab in pregnancy?

Omalizumab does not cross the placenta in the first trimester, so it will not directly affect your baby’s early development. Around 3,300 women who have used omalizumab during pregnancy have been studied. No increased risk of problems has been identified, but more research is needed to confirm this.

Some antibody treatments used in later pregnancy can affect a baby’s immune system for several months after birth. It is not yet clear whether omalizumab has this effect. As a precaution, live vaccines will usually be avoided until your baby is at least six months old.

This only applies to vaccination against rotavirus and tuberculosis, as none of the other infant vaccines are live. Your doctor can advise you about when to give your baby any live vaccines.

Alternatives

Are there any alternatives to using omalizumab in pregnancy?

Possibly. Other medicines can be used to treat asthma, but these might not have worked for you in the past. If omalizumab is controlling your asthma, your specialist may advise that staying on it during pregnancy is the best option.

If you are planning a pregnancy or have an unplanned pregnancy while taking omalizumab, speak to your specialist about which medicine is best for you.

No treatment

What if I prefer not to take medicines during pregnancy?

It is very important that asthma is well controlled during pregnancy. Poorly controlled asthma can increase the risk of complications for both you and your baby.


Your doctor will be happy to discuss any concerns about medicines prescribed during pregnancy and help you make an informed decision.

Will I or my baby need extra monitoring?

As part of routine antenatal care in the UK, women are offered a 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 due to the use of omalizumab.

Are there any risks to my baby if the father has used omalizumab?

There is currently no evidence that omalizumab used by the father can harm your baby through effects on 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 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.