Angiotensin receptor blockers (ARBs)

(Date: May 2020. Version: 3)

This factsheet has been written for members of the public by the UK Teratology Information Service (UKTIS). UKTIS is a not-for-profit organisation funded by the UK Health Security Agency (UKHSA) on behalf of UK Health Departments. UKTIS has been providing scientific information to health care providers since 1983 on the effects that medicines, recreational drugs and chemicals may have on the developing baby during pregnancy.

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. 

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

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General information 

Up to 1 out of every 5 pregnancies ends in a miscarriage, and 1 in 40 babies are born with a birth defect. These are referred to as the background population risks.  They describe the chance of these events happening for any pregnancy before taking factors such as the mother’s health during pregnancy, her lifestyle, medicines she takes and the genetic make up of her and the baby’s father into account.

Medicines use in pregnancy

Most medicines used by the mother will cross the placenta and reach the baby. Sometimes this may have beneficial effects for the baby.  There are, however, some medicines that can harm a baby’s normal development.  How a medicine affects a baby may depend on the stage of pregnancy when the medicine is taken. If you are on regular medication you should discuss these effects with your doctor/health care team before becoming pregnant.

If a new medicine is suggested for you during pregnancy, please ensure the doctor or health care professional treating you is aware of your pregnancy.

When deciding whether or not to use a medicine in pregnancy you need to weigh up how the medicine might improve your and/or your unborn baby’s health against any possible problems that the drug may cause. Our bumps leaflets are written to provide you with a summary of what is known about use of a specific medicine in pregnancy so that you can decide together with your health care provider what is best for you and your baby.   

Every pregnancy is unique. The decision to start, stop, continue or change a prescribed medicine before or during pregnancy should be made in consultation with your health care provider. It is very helpful if you can record all your medication taken in pregnancy in your hand held maternity records.

Disclaimer: This information is not intended to replace the individual care and advice of your health care provider. New information is continually becoming available. Whilst every effort will be made to ensure that this information is accurate and up to date at the time of publication, we cannot cover every eventuality and the information providers cannot be held responsible for any adverse outcomes following decisions made on the basis of this information. We strongly advise that printouts should NOT be kept for any length of time, or for “future reference” as they can rapidly become out of date.

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