Is Montelukast (Singulair) safe to use in a pregnant female patient with a history of asthma or allergic rhinitis?

Montelukast Safety in Pregnancy

Montelukast can be safely continued or initiated during pregnancy for asthma control, particularly in patients who have shown favorable response prior to pregnancy, but should be avoided for chronic rhinosinusitis or allergic rhinitis alone unless asthma is also present. 1

Primary Recommendation for Asthma

The American Congress of Obstetricians and Gynecologists and the American College of Allergy specifically recommend montelukast for recalcitrant asthma during pregnancy, especially when there has been a uniquely favorable prepregnancy response. 1, 2

• Montelukast is classified as FDA Pregnancy Category B, meaning animal studies show no teratogenic effects and no fetal risk has been demonstrated in humans, though adequate controlled studies in pregnant women are limited. 1, 3
• The drug is not teratogenic in animal studies at doses far exceeding human exposure. 1
• Poorly controlled asthma poses greater risks to maternal and fetal health (including perinatal mortality, pre-eclampsia, preterm birth, and low-birth-weight infants) than appropriate medication use. 2

Evidence on Fetal Outcomes

Major Congenital Anomalies

• The most recent 2024 meta-analysis found no significant increase in major congenital anomalies with montelukast use during pregnancy (RR 1.13,95% CI 0.74-1.73, p=0.56). 4
• A 2022 Japanese prospective cohort study of 231 pregnancies exposed to leukotriene receptor antagonists found a major congenital anomaly rate of 1.9%, with no increased risk compared to controls (adjusted OR 0.78,95% CI 0.23-2.05). 5
• A 2017 Danish population study of 401 montelukast-exposed pregnancies found no significant increase in major congenital anomalies (adjusted OR 1.4,95% CI 0.9-2.3). 6
• During worldwide post-marketing surveillance, congenital limb defects have been rarely reported, but most women were taking multiple asthma medications and no causal relationship has been established. 3

Preterm Birth and Birth Weight

• Montelukast may be associated with increased risk of preterm delivery and low birth weight (OR 1.82,95% CI 1.35-2.45), though this is likely related to maternal asthma severity rather than the medication itself. 4
• A 2009 prospective study found lower mean birth weight (3,214g vs 3,424g in non-asthmatic controls, p=0.038) and shorter gestational age, but these differences were associated with asthma severity rather than montelukast specifically. 7
• The Danish study confirmed increased risk of preterm birth in montelukast-exposed pregnancies, but this is a known complication of maternal asthma itself. 6

Other Pregnancy Outcomes

• No significant increase in spontaneous abortion risk has been demonstrated (OR 1.03,95% CI 0.72-1.5, p=0.86), though data are heterogeneous. 4
• No significant risks to neurodevelopmental outcomes have been identified. 4
• The Japanese study found no significant differences in stillbirth, spontaneous abortion, preterm birth, or low birth weight when controlling for confounders. 5

Use for Allergic Rhinitis

For allergic rhinitis without asthma, montelukast should be avoided during pregnancy. 1

• Expert consensus recommends against using anti-leukotrienes for chronic rhinosinusitis maintenance during pregnancy given lack of efficacy data and limited teratogenicity data. 1
• However, montelukast can be continued or initiated for recalcitrant asthma during pregnancy, even if allergic rhinitis is also present, especially in those with prior favorable response. 1
• For allergic rhinitis alone, safer alternatives include intranasal corticosteroids (preferably budesonide, Pregnancy Category B) or sodium cromolyn. 1, 2
• If antihistamines are needed, chlorpheniramine, cetirizine, or loratadine are preferred over levocetirizine due to better safety profiles. 8, 9, 2

Breastfeeding Considerations

Montelukast can be used during breastfeeding with minimal infant exposure. 1, 9

• Only about 1% of montelukast passes into breast milk due to extensive metabolism and plasma protein binding. 1, 9
• The benefits of breastfeeding overwhelm the minimal risk of exposure. 1
• To further limit infant exposure, consider breastfeeding prior to medication intake. 1, 9

Clinical Algorithm for Decision-Making

For Pregnant Women with Asthma:

1. If patient was on montelukast before pregnancy with good control: Continue montelukast throughout pregnancy. 1, 2
2. If patient has poorly controlled asthma despite inhaled corticosteroids: Consider initiating montelukast, particularly if there was favorable response in the past. 1, 2
3. Monitor asthma control regularly during pregnancy and adjust therapy as needed to prevent maternal and fetal complications. 9, 2

For Pregnant Women with Allergic Rhinitis Only:

1. First-line: Use intranasal budesonide or sodium cromolyn. 1, 2
2. Second-line: Use oral antihistamines (chlorpheniramine, cetirizine, or loratadine). 8, 9
3. Avoid: Montelukast for rhinitis alone unless asthma is also present. 1
4. Avoid: Oral decongestants, especially during first trimester. 1

Important Caveats

• The manufacturer maintains a pregnancy registry (800-986-8999) for monitoring outcomes of women exposed to montelukast during pregnancy, and healthcare providers are encouraged to report exposures. 3
• The primary concern is not the medication but uncontrolled maternal asthma, which significantly increases risks of adverse pregnancy outcomes. 2, 7, 4
• Montelukast should not be used for acute asthma attacks; patients must always have rescue inhalers available. 3
• Do not discontinue or reduce other asthma medications without physician guidance when starting montelukast. 3