This sheet is about exposure to mepolizumab in pregnancy and while breastfeeding. This information is based on available published literature. It should not take the place of medical care and advice from your healthcare provider.
What is mepolizumab?
Mepolizumab is a medication used with other medications to treat a severe type of asthma called eosinophilic asthma, and to treat eosinophilic granulomatosis with polyangiitis (Churg-Strauss Syndrome). A brand name of mepolizumab is Nucala®.
Mepolizumab belongs to a class of medications called monoclonal antibodies. Drugs in this class are very large proteins and it is thought that they do not cross the placenta to the fetus very well in the 1st trimester; but likely do cross later in pregnancy.
Sometimes when people find out they are pregnant, they think about changing how they take their medication, or stopping their medication altogether. However, it is important to talk with your healthcare providers before making any changes to how you take this medication. Untreated or poorly controlled asthma during pregnancy increases the chance of complications for both the person who is pregnant and the baby. Your healthcare providers can talk with you about the benefits of treating your condition and the risks of untreated illness during pregnancy. For more information about asthma, please see the MotherToBaby fact sheet at: https://mothertobaby.org/fact-sheets/asthma-and-pregnancy/.
I take mepolizumab. Can it make it harder for me to get pregnant?
It is not known if mepolizumab can make it harder to get pregnant.
Does taking mepolizumab increase the chance of miscarriage?
Miscarriage is common and can occur in any pregnancy for many different reasons. Studies have not been done to see if mepolizumab increases the chance of miscarriage.
Does taking mepolizumab increase the chance of birth defects?
Every pregnancy starts out with a 3-5% chance of having a birth defect. This is called the background risk. Studies have not been done in human pregnancy to see if mepolizumab increases the chance of birth defects. Studies in laboratory animals did not find an increased chance for birth defects when they were exposed to mepolizumab during pregnancy. There are 2 published case reports where people took mepolizumab during pregnancy and both of their babies were born healthy.
Does taking mepolizumab in pregnancy increase the chance of other pregnancy–related problems?
Studies have not been done to see if mepolizumab increases the chance for pregnancy-related problems such as preterm delivery (birth before week 37) or low birth weight (weighing less than 5 pounds, 8 ounces [2500 grams] at birth). No adverse effects on fetal growth were seen when monkeys were given mepolizumab while pregnant.
Does taking mepolizumab in pregnancy affect future behavior or learning for the child?
Studies have not been done to see if mepolizumab can cause behavior or learning issues for the child.
Breastfeeding while taking mepolizumab:
Mepolizumab has not been studied for use during breastfeeding. Mepolizumab is a very large protein, so it is thought to be unlikely that much of the medication would get into the breast milk, or would be well absorbed by the baby if they swallow small amounts in the milk. Be sure to talk to your healthcare provider about all your breastfeeding questions.
If a male takes mepolizumab, could it affect fertility or increase the chance of birth defects?
Studies have not been done to see if mepolizumab could affect male fertility (ability to get partner pregnant) or increase the chance of birth defects above the background risk. In general, exposures that fathers or sperm donors have are unlikely to increase risks to a pregnancy. For more information, please see the MotherToBaby fact sheet Paternal Exposures at https://mothertobaby.org/fact-sheets/paternal-exposures-pregnancy/.
MotherToBaby is currently conducting a study looking at medications used to treat asthma in pregnancy. If you are interested in taking part in this study, please call 1-877-311-8972 or sign up at https://mothertobaby.org/join-study/.
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OTIS/MotherToBaby encourages inclusive and person-centered language. While our name still contains a reference to mothers, we are updating our resources with more inclusive terms. Use of the term mother or maternal refers to a person who is pregnant. Use of the term father or paternal refers to a person who contributes sperm.
