Date: July 2017, Version 1

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

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.