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 called an angiotensin II receptor antagonist (ARB). Losartan has been approved to treat high blood pressure, protect the kidneys in people with diabetes, and reduce the risk 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®.
I take losartan. Can it make it harder for me to get pregnant?
Studies have not yet been done on people to see if losartan could make it harder to get pregnant. One experimental animal study did not find effects on fertility (ability to get pregnant).
I just found out I am pregnant. Should I stop taking losartan?
Taking ARBs like losartan during the second and third trimesters of a pregnancy could cause problems. For this reason, it is recommended that a person who is pregnant stop taking losartan, with their healthcare provider’s guidance, once they find out they are pregnant. However, talk with your prescribing healthcare provider before you stop taking losartan. If you are taking losartan for high blood pressure, your healthcare provider might need to prescribe a different medication to control the high blood pressure during pregnancy. Untreated high blood pressure can also cause problems for the pregnancy.
Does taking losartan increase the chance for miscarriage?
Miscarriage can occur in any pregnancy. 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. There are 19 case reports with normal outcomes after first trimester exposure to losartan (the medication was not used throughout pregnancy). One small study that looked at 20 pregnancies exposed to the class of ARB medications reported one major birth defect, which was a skull abnormality called craniosynostosis. Some of the people in this study had diabetes, a medical condition that is known to increase the chance for birth defects. Using losartan in the 2nd and 3rd trimesters might increase the chance for other pregnancy complications, such as low amniotic fluid (the fluid that surrounds the baby), which could cause birth defects. This is discussed in more detail below.
Could taking losartan cause other pregnancy complications?
Case reports of losartan use in the 2nd and/or 3rd trimester of pregnancy have found that it can cause low levels of amniotic fluid. Low levels of amniotic fluid can lead to health problems for the developing baby. These problems can include poor lung and skull development, joint contractures, growth restriction, and facial deformities. There is also a report of stillbirth. Losartan may also cause low blood pressure, kidney disease, and kidney failure in the baby after delivery. In some cases, the baby died from these complications.
Does taking losartan in pregnancy cause long-term problems in behavior or learning for the baby?
It is not known if losartan can cause behavior or learning issues.
Can I breastfeed while taking losartan?
Losartan has not been studied for use during breastfeeding in humans. Experimental animal studies have found that losartan can get into milk and could affect the kidneys of the nursing baby. Because there are no human data, talk with your healthcare providers to see if there are other medications that might be used to treat your medical condition if you plan to breastfeed. Be sure to talk to your healthcare provider about all of 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. 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 recognizes that not all people identify as “men” or “women.” When using the term “mother,” we mean the source of the egg and/or uterus and by “father,” we mean the source of the sperm, regardless of the person’s gender identity.
