(Date: July 2016. 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?

Lymecycline (Tetralysal®) is an antibiotic that is used to treat a wide range of infections, including in the treatment of acne.

Is it safe to take lymecycline in pregnancy?

Lymecycline is not often used during pregnancy, particularly in the second or third trimesters, as use of the related antibiotic tetracycline during this period is known to cause a baby’s milk teeth to be permanently stained and discoloured when they come through after birth. Occasionally, however, it may be necessary to use lymecycline to treat an infection during pregnancy (e.g. if no other antibiotic is likely to clear the infection fully). Effective treatment of potentially severe infections during pregnancy is crucial to the health of both mother and baby.

When deciding whether or not to take lymecycline during pregnancy it is important to weigh up how necessary lymecycline is to your health against the possible risks to you or your baby, some of which will depend on how many weeks pregnant you are. Your doctor is the best person to help you decide what is right for you and your baby.

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

Can taking lymecycline in early 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.

No link between lymecycline use in pregnancy and birth defects in the baby is known about, however no scientific studies have been carried out that have specifically investigated this and research into this subject is therefore required. Lymecycline belongs to a group of antibiotics called tetracyclines. Studies of tetracyclines as a group have not provided evidence of an increased overall risk of birth defects in the baby following exposure in early pregnancy. However, research into rates of specific birth defects following exposure to tetracycline antibiotics is required before an increased risk can be ruled out. It is also unclear whether the information about tetracyclines as a group can be applied specifically to lymecycline exposure.

What problems can taking lymecycline in the second or third trimesters cause in my baby?

Discolouration of the teeth
Use of lymecycline during the second or third trimesters of pregnancy can potentially discolour the unborn baby’s developing milk teeth and prevent the enamel from forming properly. This means that when the baby’s milk teeth come through they might be stained grey, brown or yellow. The baby’s second set of ‘permanent teeth’ will be unaffected.

Effects on bone growth
Lymecycline taken in pregnancy accumulates in the developing baby’s bones and there are concerns that this may affect a baby’s bone growth. Although there are one or two reports of babies exposed to tetracycline (a related antibiotic) in the womb being born with bone problems, it is not clear whether the tetracycline definitely caused them. It has also been shown that tetracycline given to newborn babies temporarily alters their bone growth, but that this returns to normal once the tetracycline is stopped. Until more pregnant women taking lymecycline are studied we cannot say whether lymecycline use during pregnancy is likely to have long-term effects on a baby’s bone growth.

Can taking lymecycline in pregnancy cause miscarriage, stillbirth, preterm birth, or my baby to be small at birth (low birth weight)?

No links between lymecycline use in pregnancy and any of the above pregnancy outcomes are known about, however no scientific studies have been carried out that have specifically investigated this and more research is therefore required.

Can taking lymecycline 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 link with learning and behavioural problems (e.g. autism spectrum disorder [ASD] and attention deficit hyperactivity disorder [ADHD]) is known about in children who were exposed to lymecycline while in the womb, however no studies have been carried out to specifically investigate this.

What if I have/am already taking lymecycline during pregnancy?

It is important not to make any changes to your treatment without speaking to your doctor first. The possible effects on a baby, described above, will depend on how many weeks pregnant you are. If you have taken any medicines it is always a good idea to let your doctor know that you are pregnant so that you can decide together whether to continue the medicine(s) that you are on or to change to another medicine if necessary.

Will my baby need extra monitoring during pregnancy?

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.

There is no evidence that taking lymecycline during pregnancy causes any problems that would require extra monitoring of your baby. 

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

We would not expect any increased risk to your baby if the father took lymecycline before or around the time you became pregnant.

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

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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