(Date: March 2015. Version: 1)

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 Public Health England 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 a medicine used to treat arrhythmia (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?

There is no yes or no answer to this question. For some pregnant women with heart arrhythmias, or where an abnormally fast heartbeat has been detected in the unborn baby, treatment with flecainide in pregnancy might be necessary. When deciding whether or not to take flecainide during pregnancy it is important to weigh up how necessary flecainide is to your or your baby’s health against the possible risks, some of which will depend on how many weeks pregnant you are.

This leaflet summarises the available scientific information relating to the effects of flecainide on a baby in the womb. It is advisable to consider this information if you are taking flecainide and are pregnant or could become pregnant in the future.

Your doctor is the best person to help you decide what is right for you and your baby.

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 appropriate dose.

It is very important that you do not stop or alter the dose of any medicine you are taking without first speaking to your doctor. If you are already pregnant, making changes to your medicine yourself may be more harmful to both you and your baby than continuing to take that medicine.

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.

It is currently unclear whether flecainide use in pregnancy can cause birth defects in the baby. Only three women who took flecainide in early pregnancy have been studied. None of the 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 risk of birth defects in the baby.

Can taking flecainide in pregnancy cause miscarriage?

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

Can taking flecainide in pregnancy cause stillbirth?

A very small study showed that rates of stillbirth were similar 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 abnormal heart rhythms which may have caused their deaths. More research needs to be done to assess the risk of stillbirth following flecainide treatment in pregnancy.

Can taking flecainide in pregnancy cause preterm birth?

No studies have investigated whether preterm birth (before 37 weeks) is more likely with use of flecainide in pregnancy.

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

A very small study showed similar birth weights in babies born to women who took flecainide in pregnancy and women who took other medicines for heart arrhythmias. Although this is reassuring, more research into the possible effects of flecainide exposure on a baby’s birth weight needs to be carried out to confirm this finding.

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.

It is currently unclear whether flecainide exposure in the womb causes alterations to learning and behaviour as no studies have been carried out to investigate this. There are a number of case reports which describe children who were developing normally after being exposed to flecainide in the womb. Two babies with abnormal development after being exposed in the womb to flecainide have also reported. However, in both of these cases other health issues might also have explained the developmental problems. More research is required to determine whether flecainide exposure in the womb might affect a child’s learning or behaviour. 

Will 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 anomaly scans around 12 weeks of pregnancy. It is, however, harder to see birth defects when the baby is still so small, which is why the main scan for birth defects is generally offered at around 20 weeks of pregnancy. It is important to understand that scans are not able to pick up all birth defects and cannot predict whether a baby will have problems with learning and behaviour.

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?

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 www.uktis.org.  

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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