(Date of issue: July 2016. 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 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 are they?
The macrolides are a group of antibiotics that include azithromycin (Zithromax®), clarithromycin (Klaricid®), erythromycin (Erymax®, Erythrocin®, Erythroped®), spiramycin (Rovamycin®), and telithromycin (Ketek®). Macrolides are used to treat infections of the sinuses, middle ear, throat, tonsils, lungs, and skin. Azithromycin is also commonly used in the treatment of chlamydia, and clarithromycin in the eradication of a specific type of bacteria that can cause stomach ulcers (Helicobacter pylori). Erythromycin is the macrolide that is most commonly prescribed during pregnancy.
Is it safe to use macrolides in pregnancy?
Erythromycin is the macrolide antibiotic which is most commonly used in pregnancy and for which the most information has been collected. Although there is less information for the other macrolides there is currently no established risk to a baby in the womb. Occasionally it may be necessary to use a macrolide other than erythromycin to treat an infection in pregnancy (e.g. if erythromycin is not 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 a macrolide during pregnancy it is important to weigh up how necessary this 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 macrolide antibiotics on a baby in the womb.
What if I have already taken a macrolide antibiotic during pregnancy?
Macrolide antibiotics are commonly used in pregnancy and would not be expected to harm a baby in the womb. However it is always a good idea to let your doctor know that you are pregnant if you have taken any medicines in case you need any additional monitoring or treatment.
Can taking a macrolide antibiotic 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.
Studies which together included babies of over 4,000 pregnant women who took a macrolide antibiotic in early pregnancy found that birth defects were no more common than in babies of women not taking macrolides. Four studies have also all shown no link between taking a macrolide antibiotic in pregnancy and the baby having a heart defect.
Some studies have assed specific macrolide antibiotics individually (rather than as a combined group). These studies found no link between taking azithromycin, clarithromycin, or erythromycin in pregnancy and the occurrence of birth defects generally in the baby, or of heart defects specifically.
Can taking a macrolide antibiotic in pregnancy cause miscarriage?
A single study of pregnant women taking azithromycin showed that they were not at increased risk of miscarriage compared to women not taking azithromycin. Two studies of pregnant women using clarithromycin both showed a possible link with miscarriage. However, none of the three studies used modern methods to accurately assess miscarriage rates. In addition, in two of the three studies, the strong possibility that the underlying infections in the mothers might have increased the likelihood of miscarriage was not accounted for. There are no published studies on miscarriage rates in women using other macrolide antibiotics. Further large studies using accurate analysis methods are therefore required to answer this question.
It important to remember that the risk of harm to you and your baby from an untreated infection may be far greater than any risk from using an antibiotic in pregnancy. Your doctor will be able to help you weigh up the risks and benefits of treatment.
Can taking a macrolide antibiotic in pregnancy cause stillbirth?
Two small studies have each shown that use of either clarithromycin or erythromycin in pregnancy does not increase the risk of stillbirth. Because stillbirth rates have been studied in only a small number of pregnant women using these antibiotics, further research is required to confirm these findings.
Can taking a macrolide antibiotic in pregnancy cause preterm birth?
All three studies which investigated this found that women who used any macrolide during pregnancy were no more likely to give birth preterm than women not using antibiotics. Two small studies also showed that use of either azithromycin or erythromycin in pregnancy did not increase the risk of preterm birth. Because preterm birth rates have been studied in a relatively small number of pregnant women using these antibiotics, and there is currently very little information on specific macrolides, further research is required to confirm these findings.
Can taking a macrolide antibiotic in pregnancy cause my baby to be small at birth (low birth weight)?
All three studies that addressed this question found that women who used any macrolide during pregnancy were not at increased risk of having a baby with reduced birth weight compared to women not using antibiotics. Two small studies have also shown that babies born to women who used azithromycin or erythromycin in pregnancy had similar birth weights to babies born to women not using these antibiotics. Because birth weight has been studied in a relatively small number of babies born to pregnant women using macrolides, and there is currently very little information on specific macrolides, further research is required to confirm these findings.
Can taking a macrolide antibiotic 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.
Studies that have investigated whether children who were exposed in the womb to macrolide antibiotics are at increased risk of learning and behavioural problems compared to children not exposed to macrolides have produced mixed findings. However, most of these studies were of antibiotic use in women who had gone into premature labour. Because preterm birth has itself been linked to an increased risk of learning and behavioural problems in children, it is currently unclear whether the effects seen in some studies may have been due to the prematurity of the baby rather than to macrolide use by the mother during pregnancy. Further research into this subject is therefore required.
Will my baby need extra monitoring during pregnancy or after delivery?
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 macrolide antibiotic 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 macrolide antibiotic?
We would not expect any increased risk to your baby if the father took a macrolide antibiotic 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 www.uktis.org.
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.