(Date: August 2019. Version: 2)

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 is it?

Flecainide (Tambocor®) is used in people with an arrhythmia (an abnormal heart rhythm). Flecainide is also occasionally given to a pregnant woman to treat an abnormally fast heartbeat in the unborn baby.

Is it safe to take flecainide in pregnancy?

For some pregnant women with a heart arrhythmia, or where an abnormally fast heartbeat has been detected in the unborn baby, treatment with flecainide might be offered by a specialist. When deciding whether or not to use flecainide during pregnancy your doctor will help you to weigh up how necessary flecainide is to your or your baby’s health against the possible risks, some of which may depend on how many weeks pregnant you are.

What if I have already taken flecainide during pregnancy?

If you are pregnant and are taking flecainide or any other medicines you should let your doctor know as soon as possible so that your medication can be reviewed to ensure you are on the most suitable medicine(s) and are taking the most effective dose.

Can taking flecainide in pregnancy cause birth defects in the baby?

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.

Only three women who took flecainide in early pregnancy have been studied. None of their babies had birth defects, but large scientific studies of pregnant women taking flecainide need to be carried out before we can say whether or not flecainide increases the chance of birth defects in the baby.

Can taking flecainide in pregnancy cause miscarriage?

No studies have investigated the likelihood of miscarriage following use of flecainide in early pregnancy.

Can taking flecainide in pregnancy cause stillbirth?

A very small study showed that the chance of having a stillbirth did not differ between pregnant women being treated with flecainide and women being treated with other medicines for heart arrhythmias. There are a number of case reports of babies dying in the womb after being exposed to flecainide. However, all of the babies had an abnormal heart rhythm which may have caused their deaths. More research needs to be done to assess the chance of stillbirth following flecainide treatment in pregnancy.

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

No studies have investigated whether preterm birth (before 37 weeks) or low infant birth weight (<2,500 g) is more likely with use of flecainide in pregnancy.

Can taking flecainide in pregnancy cause learning and 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 assessed whether flecainide exposure in the womb might affect a child’s learning and behaviour. There are a number of case reports describing children who were developing normally after being exposed to flecainide in the womb, and also reports of two babies with abnormal development. However, in both of these cases, other health issues might have explained the developmental problems. More research into the learning and behaviour of children exposed in the womb to flecainide is required.

Will I or my baby need extra monitoring?

As part of their routine antenatal care most women will be offered a scan at around 20 weeks of pregnancy to look for birth defects and to check the baby’s growth. Women with serious heart arrhythmias are likely to be monitored more closely during pregnancy to ensure that they remain well throughout and that their baby is growing and developing as expected. Where an abnormally fast heartbeat has been detected in the baby, extra monitoring will be required to determine the need for treatment and to ensure that the baby has not developed a condition called fetal hydrops. This is where abnormal fluid levels build up in the baby’s body due to the heart not working effectively.

Because the effects of flecainide on a developing pregnancy are largely unknown, if you are treated with flecainide in early pregnancy, your doctor may wish to monitor you more closely and may offer you the option of having more detailed scans.

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

No studies have specifically investigated whether flecainide used by the father can harm the baby through effects on the sperm, however most experts agree that this is very unlikely. More research on the effects of medicine use in men around the time of conception is needed.

Who can I talk to if I have questions?

No studies have specifically investigated whether flecainide used by the father can harm the baby through effects on the sperm, however most experts agree that this is very unlikely. More research on the effects of medicine use in men around the time of conception is needed.

Who can I talk to if I have questions?

If you have any questions about the information in this leaflet please discuss them with your health care provider. They can access more detailed medical and scientific information from www.uktis.org.  

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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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