Date: April 2020, Version 3

What is it?

Montelukast (Singulair®) is prescribed for people with asthma, usually when symptoms are not fully controlled with inhalers.

Is it safe to use montelukast in pregnancy?

When deciding whether to use montelukast during pregnancy it is important to weigh up the potential benefits to your health and wellbeing against any possible risks to you or your baby, some of which may depend on how many weeks pregnant you are.

Uncontrolled or poorly controlled asthma in pregnancy has been linked to a number of adverse outcomes including stillbirth, preterm birth, low birth weight in the baby, and preeclampsia in the mother. Good control of asthma in pregnancy is therefore vital. Your doctor or specialist will be able to help you make decisions about your treatment.

What if I have already taken montelukast during pregnancy?

If you are taking any medicines while pregnant, you can discuss this with your doctor. You can then decide together whether ongoing treatment is appropriate, and if so, your doctor will ensure that you are taking the most effective dose.

Can using montelukast 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 that include at least 1,000 pregnant women do not raise concern that exposure to montelukast in early pregnancy is linked to birth defects in the baby. However, ongoing research is ideally required to confirm this.

Can taking montelukast in pregnancy cause miscarriage?

Two small studies found no link between miscarriage and use of montelukast in early pregnancy. However, as only around 250 women were studied in total, more research is required to confirm this finding.

Can taking montelukast in pregnancy cause stillbirth?

No studies have investigated the likelihood of stillbirth following exposure to montelukast in pregnancy.

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

A single study found that women who used montelukast during pregnancy may be more likely to have a preterm birth and therefore a baby with a low birth weight (preterm babies tend to be smaller). However, these pregnancy outcomes have been linked to asthma itself. Further research is therefore required to determine whether use of montelukast can directly cause preterm birth and related low infant birth weight, or whether these effects are linked to asthma in the mother.

Can taking montelukast 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 the learning and behaviour of children exposed in the womb to montelukast.

Will my baby need extra monitoring during pregnancy?

Most women will be offered a scan at around 20 weeks of pregnancy to look for birth defects as part of their routine antenatal care. Taking montelukast in pregnancy is not expected to cause problems that would require extra monitoring of your baby.

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

No studies have specifically investigated whether montelukast 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

How can I help to improve drug safety information for pregnant women in the future?

Our online reporting system (MyBump Portal) allows women who are currently pregnant to create a secure record of their pregnancy, collected through a series of questionnaires. You will be asked to enter information about your health, whether or not you take any medicines, your pregnancy outcome and your child's development. You can update your details at any time during pregnancy or afterwards. This information will help us better understand how medicines affect the health of pregnant women and their babies. Please visit the MyBump Portal to register.

General information
Sadly, miscarriage and birth defects can occur in any pregnancy.

Miscarriage occurs in about 1 in every 5 pregnancies, and 1 in every 40 babies are born with a birth defect. This is called the ‘background risk’ and happens whether medication is taken or not.

Most medicines cross the placenta and reach the baby. For many medications this is not a problem. However, some medicines can affect a baby’s growth and development.

If you take regular medication and are planning to conceive, you should discuss whether your medicine is safe to continue with your doctor/health care team before becoming pregnant. If you have an unplanned pregnancy while taking a medicine, you should tell your doctor as soon as possible.

If a new medicine is suggested for you during pregnancy, please make sure that the person prescribing it knows that you are pregnant. If you have any concerns about a medicine, you can check with your doctor, midwife or pharmacist.

Our Bumps information leaflets provide information about the effects of medicines in pregnancy so that you can decide, together with your healthcare provider, what is best for you and your baby.