Is Singulair (Montelukast) Safe During Pregnancy?
Montelukast is safe to use during pregnancy, particularly for recalcitrant asthma in patients who have shown favorable response prior to pregnancy, and is classified as FDA Pregnancy Category B with reassuring human safety data showing no increased risk of major congenital malformations. 1, 2
Safety Evidence and Classification
- Montelukast is FDA Pregnancy Category B, meaning animal studies have not demonstrated fetal risk, though controlled studies in pregnant women are limited 2
- The American Congress of Obstetricians and Gynecologists and the American College of Allergy both support montelukast use during pregnancy when clinically indicated, especially for recalcitrant asthma 1
- Large prospective cohort data from 180 pregnancies exposed to montelukast reported only one major congenital malformation (0.6%), which does not exceed the 1-3% baseline risk in the general population 3, 4
- A Danish population-based study of 827 montelukast-exposed pregnancies found an adjusted odds ratio for major congenital anomalies of 1.4 (95% CI 0.9-2.3) for montelukast alone and 1.0 (95% CI 0.6-1.8) when combined with other asthma medications, indicating no increased risk 3, 5
- A Japanese prospective cohort of 231 pregnancies (122 montelukast exposures) found a major anomaly rate of 1.9% with an adjusted odds ratio of 0.78 (95% CI 0.23-2.05), showing no significant association with congenital defects 3, 6
Clinical Indications During Pregnancy
For Asthma:
- Continue montelukast if it provided good asthma control before conception 1, 3
- Initiate montelukast for recalcitrant asthma when standard inhaled therapies (inhaled corticosteroids and short-acting β-agonists) fail to achieve adequate control 1, 3
- Poorly controlled asthma poses greater risks to maternal and fetal health than medication use, including perinatal mortality, pre-eclampsia, preterm birth, and low-birth-weight infants 3, 7
For Allergic Rhinitis:
- Avoid montelukast for chronic rhinosinusitis (CRS) maintenance during pregnancy due to lack of efficacy data in this condition 1
- For allergic rhinitis, prefer intranasal corticosteroids (particularly budesonide) or sodium cromolyn as first-line options 1, 7
Important Caveats and Considerations
- Post-marketing surveillance has rarely reported congenital limb defects in offspring of women taking montelukast during pregnancy, though most women were also taking other asthma medications and a causal relationship has not been established 2
- The manufacturer maintains a pregnancy registry (800-986-8999) for monitoring outcomes of women exposed to montelukast during pregnancy 2
- Montelukast crosses the placenta following oral dosing in animal studies 2
Breastfeeding Safety
- About 1% of montelukast passes into breast milk, but extensive metabolism and plasma protein binding limit infant exposure 1, 3
- The benefits of breastfeeding generally outweigh the risk of exposure 1, 7
- Consider breastfeeding prior to medication intake to further limit infant exposure 1
Treatment Algorithm for Pregnancy
If patient has well-controlled asthma on montelukast pre-pregnancy: Continue montelukast throughout pregnancy 1, 3
If patient has inadequately controlled asthma during pregnancy:
If patient has allergic rhinitis without asthma: Use intranasal corticosteroids or sodium cromolyn instead of montelukast 1, 7
Common Pitfalls to Avoid
- Do not discontinue effective asthma therapy during pregnancy out of medication fear – untreated asthma poses greater fetal risks than montelukast exposure 3, 7
- Do not use montelukast as first-line therapy for chronic rhinosinusitis during pregnancy – lack of efficacy data in this condition 1
- Do not avoid montelukast solely based on post-marketing limb defect reports – no causal relationship has been established and large cohort studies show no increased malformation risk 3, 2, 6, 5