Tetracycline

What are they?

The tetracyclines are a group of antibiotics that are used to treat many different types of bacterial infection. Tetracyclines prescribed in the UK include tetracycline, demeclocycline, doxycycline, lymecycline, minocycline, oxytetracycline and tigecycline. Doxycycline may also be prescribed to prevent malaria. 

Is it safe to take a tetracycline in pregnancy?

Tetracyclines are not often used during pregnancy, particularly in the second or third trimesters, as use 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 a tetracycline to treat an infection (e.g. if no other antibiotic is likely to clear the infection fully). Effective treatment of infections during pregnancy is crucial to the health of both mother and baby.

When deciding whether or not to take a tetracycline during pregnancy it is important to weigh up how necessary tetracycline 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.

What if I have already taken a tetracycline during pregnancy?

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 you still need the medicines that you are on and to make sure that you are taking the lowest dose that works.

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

Can taking a tetracycline 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.

A small number of studies have investigated possible links between taking tetracycline, doxycycline, and oxytetracycline in the first trimester and specific birth defects. Overall, the current evidence does not raise alarm that birth defects are caused by use of these tetracyclines in pregnancy. However, only small numbers of women have generally been studied, the results of the studies do not all agree, and some of the studies were carried out a long time ago meaning that they did not use the most up-to-date analysis techniques. Additionally, there is no information on the chance of birth defects in the baby after use of other tetracycline antibiotics. More research is therefore needed.

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

Discolouration of the teeth
It is well known that use of a tetracycline during the second or third trimesters of pregnancy can 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
Tetracyclines taken in pregnancy accumulate 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 tetracyclines in the womb being born with bone problems, it is not clear whether the tetracycline definitely caused them. It has 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 tetracyclines are studied, we cannot say whether tetracycline use during pregnancy is likely to have long-term effects on a baby’s bone growth.

Can taking a tetracycline in pregnancy cause miscarriage?

A single study found that pregnant women taking doxycycline or minocycline may have a higher chance of miscarriage compared to women taking other types of antibiotic. The study could not rule out that this may have been due to the types of infection in the women taking tetracyclines, rather than to tetracycline use itself. Further research is therefore required to confirm these findings, and studies into the possible effects of other tetracyclines are also required.

Can taking a tetracycline in pregnancy cause stillbirth?

No studies have investigated whether taking a tetracycline antibiotic in pregnancy might affect the chance of stillbirth. Research into this subject is therefore required.

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

Two studies have both shown that babies born to women taking doxycycline were no more likely to be born prematurely (before 37 weeks of pregnancy) or to have a lower birth weight compared to babies not exposed in the womb to doxycycline. Further research is required to confirm these findings and studies into the potential effects of other tetracyclines are also required.

Can taking tetracycline 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 been carried out to investigate learning and behaviour in children exposed in the womb to tetracyclines.

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 a tetracycline 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 a tetracycline?

We would not expect any increased risk to your baby if the father took a tetracycline 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 healthcare provider. They can access more detailed medical and scientific information from www.uktis.org.