The information provided below is for readers based in the United States of America. Readers outside of the United States of America should seek the information from local sources.

This medication is considered to have a low risk when used during pregnancy

What is montelukast?

Montelukast is a leukotriene receptor antagonist that treats chronic asthma and allergies.

What is montelukast used to treat?

Montelukast is a prescription medication used to prevent and treat asthma and nasal allergy symptoms.

How does montelukast work?

Montelukast blocks production of a chemical (leukotriene) in the body that causes signs and symptoms of asthma such as respiratory inflammation and chest tightness.

If I am taking montelukast, can it harm my baby?

Animal studies find no association between montelukast use during pregnancy and birth defects. The American Congress of Obstetricians and Gynecologists and the American College of Allergy, Asthma, and Immunology released a position statement in 2000 that recommended montelukast in pregnant women with difficult-to-treat asthma who had success taking the medication before pregnancy. Pregnant women with uncontrolled asthma also have an increased risk of preeclampsia and preterm birth. A Danish study in asthmatic women taking montelukast through the first trimester of pregnancy found a higher risk of maternal complications such as preeclampsia and preterm birth (side effects similar to women with uncontrolled asthma during pregnancy).

It is unknown if montelukast crosses the placenta to reach the baby. Studies of women exposed to montelukast during pregnancy have not proven a link to an increased risk of birth defects such as limb defects. Many of the reports of infants born with limb defects were in mothers who took several asthma medications. One study in 180 pregnant women found an increased risk of babies born with low birth weight and distress during delivery with montelukast exposure. Studies have not identified an increased risk of major birth defects such as cardiac abnormalities with in utero montelukast exposure.

If I am taking montelukast and become pregnant, what should I do?

It is important that you speak with your doctor and decide if you should still take montelukast during pregnancy. Some women with difficult-to-treat asthma who’ve had success with montelukast before pregnancy may require continuation of the medication during pregnancy.

If I am taking montelukast, can I safely breastfeed my baby?

The effect of montelukast on breastfeeding infants is unknown. In a study of seven women taking montelukast during breastfeeding, infant doses were estimated to be 0.68% of the mother’s dose. It is important to weigh the risks and benefits of taking montelukast while breastfeeding since limited information is available. Montelukast is also used in children with asthma.

If I am taking montelukast, will it be more difficult to get pregnant?

Animal studies showed decreased fertility in females given high doses of montelukast, but this effect was not seen in males or females given lower doses of the medication.

If I am taking montelukast, what should I know?

It is generally thought that montelukast should be safe during pregnancy, but there is limited information available in humans. Montelukast should only be used during pregnancy if the benefits to the mother outweigh the risks to the developing baby.

If I am taking any medication, what should I know?

This report provides a summary of available information about the use of montelukast during pregnancy and breastfeeding. Content is from the product label unless otherwise indicated.

You may find Pregistry's expert report about asthma here, and reports about the individual medications used to treat respiratory disorders here.   Additional information can also be found in the resources below. 

For more information about montelukast during and after pregnancy, contact (800-994-9662 [TDD: 888-220-5446]) or check the following link:

Merck: Singulair Prescribing Information

Read the whole report
General information

It is very common for women to worry about having a miscarriage or giving birth to a child with a birth defect while they are pregnant. Many decisions that women make about their health during pregnancy are made with these concerns in mind.

For many women these concerns are very real. As many as 1 in 5 pregnancies end in a miscarriage, and 1 in 33 babies are born with a birth defect. These rates are considered the background population risk, which means they do not take into consideration anything about the health of the mom, the medications she is taking, or the family history of the mom or the baby’s dad. A number of different things can increase these risks, including taking certain medications during pregnancy.

It is known that most medications, including over-the-counter medications, taken during pregnancy do get passed on to the baby. Fortunately, most medicines are not harmful to the baby and can be safely taken during pregnancy. But there are some that are known to be harmful to a baby’s normal development and growth, especially when they are taken during certain times of the pregnancy. Because of this, it is important to talk with your doctor or midwife about any medications you are taking, ideally before you even try to get pregnant.

If a doctor other than the one caring for your pregnancy recommends that you start a new medicine while you are pregnant, it is important that you let them know you are pregnant.

If you do need to take a new medication while pregnant, it is important to discuss the possible risks the medicine may pose on your pregnancy with your doctor or midwife. They can help you understand the benefits and the risks of taking the medicine.

Ultimately, the decision to start, stop, or change medications during pregnancy is up to you to make, along with input from your doctor or midwife. If you do take medications during pregnancy, be sure to keep track of all the medications you are taking.