This sheet is about exposure to losartan in pregnancy and while breastfeeding. This information should not take the place of medical care and advice from your healthcare providers.
What is losartan?
Losartan is a medication that is part of a group of medications called angiotensin II receptor antagonists (also known as angiotensin receptor blockers (ARBs)). Losartan has been approved to treat high blood pressure, protect the kidneys in people with diabetes, and lower the chance of cerebrovascular accident (when the supply of blood to the brain is reduced or blocked). Losartan is also prescribed for other medical reasons. A brand name for losartan is Cozaar®. Losartan is also available in combination with a diuretic called hydrochlorothiazide under the brand name Hyzaar®.
It is usually recommended that people who are pregnant stop taking losartan under their healthcare provider’s guidance. However, it is important to talk with your healthcare providers before making any changes to how you take this medication. Your healthcare providers can talk with you about the benefits of treating your condition and the risks of untreated illness during pregnancy.
I take losartan. Can it make it harder for me to get pregnant?
It is not known if losartan can make it harder to get pregnant. One animal study did not find effects on fertility (ability to get pregnant).
Does taking losartan increase the chance for miscarriage?
Miscarriage is common and can occur in any pregnancy for many different reasons. Based on the studies reviewed, it is not known if losartan increases the chance for miscarriage.
Does taking losartan 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. Losartan has not been well studied for use during pregnancy. Based on the studies reviewed, it is not known if losartan can increase the chance of birth defects when used in the first trimester of pregnancy. There are case reports with typical outcomes after first trimester exposure to losartan when the medication was not used throughout pregnancy. One small study that looked at 20 pregnancies exposed to the class of ARB medications reported one infant with craniosynostosis (when the bones in the skull join together too early) and another with inguinal hernia (when soft tissue bulges through a weak place in the belly muscles). Some of the people in this study had diabetes, which has also been linked to an increased chance for birth defects. It is not known if the medication taken, or other factors caused the reported birth defects.
Using losartan in the 2nd and 3rd trimesters can increase the chance for other pregnancy complications, such as low amniotic fluid (the fluid that surrounds the baby). Low amniotic fluid levels could cause birth defects. This is discussed in more detail below.
Does taking losartan in pregnancy increase the chance of other pregnancy-related problems?
Based on the studies reviewed, use of losartan in the 2nd and/or 3rd trimester of pregnancy can cause other pregnancy-related problems, such as low levels of amniotic fluid (called oligohydramnios). Low levels of amniotic fluid can lead to poor lung and skull development, joint contractures (joints become stiff and unable to move), and growth restriction in the fetus. Oligohydramnios can also increase the need for an early delivery through induction of labor or C-section. In some cases, oligohydramnios could cause fetal demise.
Low blood pressure, kidney disease, and kidney failure has been reported in babies exposed to losartan during pregnancy. In some cases, the affected infant died from these complications.
Because of these possible complications, it is usually recommended that people who are pregnant stop taking losartan under their healthcare provider’s guidance. It is important to talk with your healthcare provider before you stop taking losartan. They can talk with you about the best way to treat your condition during pregnancy. Some untreated conditions can also increase risks to a pregnancy.
Does taking losartan in pregnancy affect future behavior or learning for the child?
Studies have not been done to see if losartan can cause behavior or learning issues for the child.
Breastfeeding while taking losartan:
Losartan has not been studied in humans for use during breastfeeding. Information from animal studies suggest that losartan passes into milk and might affect the kidneys of the nursing baby. The product label for losartan recommends people who are breastfeeding not use this medication. But the benefit of using losartan may outweigh possible risks. Your healthcare providers can talk with you about using losartan and what treatment is best for you. Be sure to talk to your healthcare provider about all your breastfeeding questions.
If a male takes losartan, could it affect fertility (ability to get partner pregnant) or increase the chance of birth defects?
This has not been well studied. Based on the studies reviewed, it is not known if losartan could affect male fertility or increase the chance of birth defects above the background risk. In general, exposures that fathers or sperm donors have are unlikely to increase the risks to a pregnancy. For more information, please see the MotherToBaby fact sheet Paternal Exposures at https://mothertobaby.org/fact-sheets/paternal-exposures-pregnancy/.
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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.