ACE inhibitors

(Date: April 2018. 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 ACE inhibitors?

ACE inhibitors are medicines that treat high blood pressure, heart failure, and kidney disease. Some products (marked in the list below with*) combine an ACE inhibitor with another type of medicine. This leaflet summarises the scientific studies relating to the effects that ACE inhibitors may have on a baby when taken by the mother in pregnancy. Any potential effects of the additional components in the combination medicines are not discussed in this leaflet.

ACE inhibitors available in the UK include; captopril [Capoten®,Co-zidocapt®*,Capozide®*], cilazapril [Vascace®], enalapril maleate [Innovace®, Innozide®*], fosinopril sodium, imidapril hydrochloride [Tanatril®],  lisinopril [Zestril®, Carace Plus®*, Zestoretic®*], moexipril hydrochloride [Perdix®], perindopril erbumine, perindopril arginine [Coversyl® Arginine, Coversyl® Arginine Plus*], quinapril [Accupro®, Accuretic®*], ramipril [Tritace®, Triapin®*], trandolapril [Gopten®, Tarka®*].

Is it safe to take an ACE inhibitor in pregnancy?

Use of ACE inhibitors in the second and third trimesters is not advised but may occasionally be necessary for serious illnesses if other treatments have not worked. Any woman who is taking an ACE inhibitor and is planning a pregnancy should speak to her doctor to discuss the possibility of switching to a different medicine before she conceives. Some women may need to take an ACE inhibitor during pregnancy. Your doctor and/or obstetrician will be able to help you weigh up how necessary an ACE inhibitor is to your health against the possible risks to your baby.

This leaflet summarises the scientific studies relating to the effects of ACE inhibitors on a baby in the womb.

What if I have already taken an ACE inhibitor during pregnancy?

If you have taken an ACE inhibitor in the second or third trimester of pregnancy without medical supervision, it is important to let your doctor or midwife know straight away as your baby may need extra monitoring for the effects described below. 

There is no good evidence that taking ACE inhibitors during the first trimester will harm a baby in the womb. However, you should let your doctor know that you are pregnant so that you can decide together whether you should change to another safer medicine for the remainder of your pregnancy. It is important that your doctor reviews all medicines that you are taking if you become pregnant to assess whether you still need them.

Can taking ACE inhibitors in pregnancy cause miscarriage?

It is unclear whether taking ACE inhibitors in early pregnancy increases the chance of having a miscarriage. Two small studies both showed that women who take ACE inhibitors or a related type of medicine during early pregnancy may be more likely to have a miscarriage than women who have not taken any medicines. However, only 350 pregnancies were studied in total and women taking ACE inhibitors were not studied separately from women taking other medication for high blood pressure. More research into the specific effects of ACE inhibitors is required to answer this question.

ACE inhibitors are used to treat high blood pressure and diabetes, both of which are more common in people with obesity. High blood pressure, diabetes and obesity increase a woman’s chance of having a miscarriage. More research is needed to understand whether the reported increased risk of miscarriage is due to the medicines the pregnant women were taking, their health problems, or a combination of both factors.

Can taking ACE inhibitors in pregnancy cause my baby to be born with birth defects?

A baby’s body and most internal organs are formed during the first 12 weeks of pregnancy. It is mainly during this time that some medicines are known to cause birth defects.

Analysis of over 4,000 women taking ACE inhibitors in early pregnancy has not shown a greater risk of having a baby with a birth defect compared to the background risk. Furthermore:

• Studies of around 3,800 women have provided no evidence of a direct link between use of ACE-inhibitors in early pregnancy and heart defects in the baby
• A study suggested that babies born to women who took ACE inhibitors in early pregnancy may be more likely to have defects of the central nervous system, however another larger study did not agree with this finding
• A study which investigated the chance of a specific type of nervous system defect called a neural tube defect found no link with ACE inhibitors
• A study suggested that babies whose mothers had taken ACE inhibitors during early pregnancy may be more likely to have a kidney defect. However, no other studies have investigated this link and further research is needed

In summary, there is no good evidence that first trimester use of an ACE-I causes birth defects.

What problems can taking ACE inhibitors after the first trimester of pregnancy cause for my baby?

Taking ACE inhibitors during the second and third trimesters can cause a number of problems in the baby including:

• Kidney damage which can lead to long-term kidney problems after birth
• Reduced growth of the baby in the womb
• A problem with the newborn baby’s circulation called patent ductus arteriosus. This is caused by a blood vessel staying open after birth (when it should close)
• Reduced levels of amniotic fluid around the baby in the womb (oligohydramnios) which may then lead to:

• Underdevelopment of the baby’s skull bones
• Poor development of the baby’s lungs
• The baby’s bladder being underdeveloped
• The baby’s skull and leg bones being misshapen and the baby having ‘flattened’ facial features as a result of there not being enough amniotic fluid to ‘cushion’ the baby in the womb

ACE inhibitors should only be taken after the first trimester under strict medical supervision. Some of the pregnancy problems discussed above (e.g. low levels of amniotic fluid) can be detected by ultrasound scans. Regular monitoring of your baby will be required to allow ongoing decisions to be made about treatment for your and your baby’s health. Please discuss any concerns that you may have with your doctor.

Can taking ACE inhibitors in pregnancy cause preterm birth or my baby to be small at birth (low birth weight)?

Two small studies have linked use of ACE inhibitors or related medicines during early pregnancy with earlier delivery and lower than average birth weight in the baby. However, these effects have been seen in women taking other blood pressure medications. High blood pressure in the mother may affect the growth of the baby. Early delivery is more likely in women with high blood pressure due to concerns about the mother’s or baby’s health.

Use of ACE inhibitors in the second and third trimesters has been linked to intrauterine growth restriction but it is difficult to separate the effects of the ACE inhibitor from the mother's illness.

Can taking ACE inhibitors in pregnancy cause learning or behavioural problems in the child?

A baby’s brain continues to develop right up until the end of pregnancy. It is therefore possible that taking certain medicines at any stage of pregnancy could have a lasting effect on a child’s learning or behaviour.

 No studies have investigated learning and behaviour in children exposed to ACE inhibitors in the womb.

Will my baby need extra monitoring during pregnancy?

All women are offered a scan at around 20 weeks of pregnancy to look for birth defects as part of their routine antenatal care. This would pick up the majority of birth defects and would be adequate screening for women taking ACE inhibitors in the first trimester. Extra growth scans will be required in women who continue to take ACE inhibitors in pregnancy. These babies will require delivery in a maternity unit where there is a co-located neonatal unit. 

Are there any risks to my baby if the father has taken ACE inhibitors?

We would not expect any increased risk to your baby if the father took ACE inhibitors before or around the time your baby was conceived.

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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