Angiotensin receptor blockers (ARBs)

Date: May 2020, Version 3

What are they?

Angiotensin II receptor blockers (ARBs) (such as azilsartan, candesartan, eprosartan, irbesartan, losartan, olmesartan, telmisartan, and valsartan) are used treat high blood pressure, heart failure, kidney disease and to prevent migraines.

Is it safe to use an ARB in pregnancy?

No, ARBs should not be used in pregnancy.  If you are taking an ARB and planning a pregnancy, you should speak to your GP or hospital consultant to discuss the possibility of switching to a different medicine before trying to become pregnant.

If you discover that you are pregnant whilst taking an ARB, you should contact your doctor as soon as possible so that you can be switched to another medicine.

If you have taken an ARB in the second or third trimester of pregnancy it is important to let your doctor or midwife know straight away as your baby will need extra monitoring (see below).


What are the risks of taking an ARB in pregnancy?

Taking an ARB during the second and third trimesters (specifically from around 20 weeks of pregnancy) can cause a number of problems in the baby:

• Reduced levels of amniotic fluid around the baby in the womb (oligohydramnios)

• Damage to the baby’s kidneys which can lead to long-term kidney problems after birth
• Under-development of the skull bones

• Reduced growth in the womb

• Under-development of the lungs

• Contracted (stiffened) joints

Studies show that up to one in every three babies exposed in the womb to an ARB after 20 weeks of pregnancy develop some or all of these problems.

Additionally, use of ARBs in later pregnancy is linked to babies being born early and with a low birth weight. This may be due to these deliveries being induced early, rather than a direct effect of the medication

Some women may take an ARB before realising they are pregnant. They can feel reassured that taking ARBs in early pregnancy does not seem to be linked to miscarriage. Babies exposed in the womb to ARBs in early pregnancy do not seem to have higher chance of having a birth defect, or of preterm birth or low birth weight. However, for most of these outcomes, the study sizes are small and ongoing research is required to confirm the findings.


What are the alternatives to taking an ARB in pregnancy?

There are a number of other medicines that can be used to treat high blood pressure, heart failure, and kidney disease in pregnancy. Your specialist doctor will be able to help you decide which of these is right for you. 

No treatment

What if I prefer not to take any medicines to treat hypertension, heart failure, or kidney disease?

The medicine(s) that your doctor has advised that you use in place of an ARB will have been chosen because they are safer for the baby. It is important to take medicines prescribed for hypertension, heart failure, or kidney disease as these conditions carry a risk of serious consequences for both mother and baby. Your doctor will only prescribe medicines when absolutely necessary and will be happy to talk to you about any concerns that you might have.

Will my baby need extra monitoring?

All women in the UK are offered a detailed anomaly scan at around 20 weeks of pregnancy as part of their routine antenatal care. Women who have used an ARB in the first trimester will not require any extra monitoring.

Women who continue to take an ARB during the second or third trimester will require additional monitoring to assess amniotic fluid levels and their baby’s growth and wellbeing. 

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

We would not expect any increased risk to your baby if the father takes an ARB.

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.