(Date: July 2017. Version: 1)

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?

Eculizumab is a type of medicine called a monoclonal antibody and may also be referred to as a biologic. It is used by specialist doctors to treat two rare conditions called paroxysmal nocturnal haemoglobinuria (PNH) and atypical haemolytic-uraemic syndrome (aHUS).

Is it safe to take eculizumab in pregnancy?

Any woman who is taking eculizumab and is planning a pregnancy should ideally speak to her doctor before she conceives.

There is very little information on eculizumab use in pregnancy. However, because the disorders that eculizumab is used to treat can be life-threatening and may worsen during pregnancy, continued eculizumab treatment during pregnancy may be advised. Your doctor will be able to help you to weigh up how necessary eculizumab is to your health against the possible risks to you, such as an increased susceptibility to certain infections, or to your baby. Some of these risks will change depending on how many weeks pregnant you are at the time of taking eculizumab.

This leaflet summarises the scientific studies relating to the effects of eculizumab on a baby in the womb. 

What if I have already taken eculizumab during pregnancy?

If you have taken any medicines it is always a good idea to let your doctor know that you are pregnant so that you can decide together whether you still need the medicines that you are on and, if so, to make sure that you are taking the lowest dose that works.

Can taking eculizumab in early pregnancy cause my baby to be born with birth defects?

A baby’s body and most internal organs are formed during the first 12 weeks of pregnancy. It is mainly during this time that some medicines are known to cause birth defects.

Eculizumab is not thought to cross the placenta to the baby during the first trimester of pregnancy.

Published scientific case studies of individual patients and groups of women (case series) together provide information on a total of 109 babies born to women taking eculizumab in early pregnancy. The only baby that had a birth defect was born to a mother who was taking another medicine known to cause that type of birth defect. Although the evidence available so far does not suggest that eculizumab use in pregnancy causes birth defects, large scientific studies need to be carried out before we can fully assess the safety of eculizumab use in pregnancy.

Can taking eculizumab in pregnancy cause miscarriage?

To date, no large scientific studies have specifically assessed whether or not miscarriage is more frequent in pregnant women taking eculizumab. The information from case studies and small groups of women that have been written up in medical journals does not raise concerns but is not collected in such a way as to enable a comparison of miscarriage risk with women in the general population. Further scientific research is therefore required to accurately determine whether use of eculizumab in early pregnancy increases the chance of miscarriage.

Can taking eculizumab in pregnancy cause stillbirth?

No high quality studies have specifically analysed the occurrence of stillbirth in pregnant women taking eculizumab. Although there are a small number of reports of stillbirth in women who were treated with eculizumab in pregnancy, these women had serious illnesses that sometimes get much worse in pregnancy if not treated. The mother’s ill health may therefore be the reason for the stillbirth. These women were also likely to have been taking other medicines.

Can taking eculizumab in pregnancy cause premature birth or my baby to be small at birth (low birth weight)?

No studies have specifically analysed whether preterm birth or low birth weight babies are more common in pregnant women taking eculizumab. There are case reports of babies who were exposed to eculizumab in the womb being born prematurely (before 37 weeks) and/or having a low birth weight (<2,500g) (which can be simply due to the baby being born early). However, some of these babies were born by induced early delivery due to illness in the mother. It is therefore unclear whether taking eculizumab in pregnancy can directly cause premature birth or low birth weight in the baby.

Can taking eculizumab in pregnancy cause learning and behavioural problems in the child?

A baby’s brain continues to develop right up until the end of pregnancy. It is therefore possible that taking certain medicines at any stage of pregnancy could have a lasting effect on a child’s learning or behaviour.

No studies have been carried out to specifically investigate whether exposure to eculizumab while in the womb increases the chance of learning and behavioural problems in the child. Case reports of individual patients and case series (reports of a small group of patients) include a total of 77 children whose development was assessed between the ages of four months and around 8 years of age. One child was reported to have a speech delay, with normal development reported for the others. Although this information does not raise any concerns, larger scientific studies, specifically designed to study learning and development accurately in children exposed in the womb to eculizumab, are needed.

Will I or my baby need extra monitoring during pregnancy?

Most women will be offered a scan at around 20 weeks of pregnancy to look for birth defects as part of their routine antenatal care.

Because the effects of taking eculizumab in early pregnancy are largely unknown, your doctor may suggest extra monitoring of your baby, including more detailed scans for birth defects and monitoring of your baby’s growth in the womb.

Pregnant women with the illnesses that eculizumab is used to treat will also be more closely monitored during pregnancy to ensure that they remain well throughout and that their baby is growing and developing as expected. 

Can taking eculizumab in pregnancy cause problems with the baby’s immune system after birth?

Because of the way that eculizumab works, there is a theoretical risk that its use in pregnancy might suppress a newborn baby’s immune system and increase the risk of certain infections. No cases of worrying infection in babies exposed to eculizumab in the womb have been published, but studies designed to assess this concern are still needed.

Live vaccines can very occasionally cause the illness that they are designed to protect against, especially in people with a suppressed immune system. Therefore, as a precaution, it may be recommend that use of the rotavirus vaccine (the only live vaccine given in the UK before the age of 1 year) is delayed for up to six months in babies who were exposed in the womb to eculizumab.

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

Most experts agree that the majority of medicines used by the father are unlikely to harm the baby through effects on the sperm. However, more research on the effects of eculizumab specifically and medicine use in men around the time of conception generally is needed.

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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