• Home
  • Pamphlets and Brochures
  • Donate now
  • Frequently Asked Questions
  • Please read

Our Helplines

Motherisk Helpline
1-877-439-2744 (Toll-free)
416-813-6780 (Toronto and GTA)

Alcohol and Substance

Safety of using montelukast during pregnancy

Gideon Koren, MD FRCPC FACMT, Moumita Sarkar, PhD and Adrienne Einarson, RN

September 2010



Montelukast is used more and more by my patients with asthma. Is it safe to use during pregnancy?


Cumulative data, including a recent Motherisk study, are very reassuring regarding the use of this drug to treat pregnant patients with asthma.


De plus en plus de mes patients atteints d’asthme utilisent le montelukast. Son utilisation est-elle sans danger durant la grossesse?


Les données cumulatives, y compris celles d’une récente étude par Motherisk, sont très rassurantes quant à l’utilisation de ce médicament pour traiter l’asthme chez les patientes enceintes.

Asthma adversely affects up to 8% of all pregnancies.1,2 Approximately one-third of pregnant women with asthma remain stable, one-third experience an improvement, and one-third experience a worsening of their condition.3 Untreated asthma leads to increased risk of preterm delivery,4 preeclampsia, vaginal hemorrhage, and pregnancy-induced hypertension.37 Montelukast sodium has the advantage of once-daily dosing and oral administration.8 This selective leukotriene receptor antagonist decreases the activation of the cysteinyl leukotriene 1 receptor.9 The American College of Obstetricians and Gynecologists and the American College of Allergy, Asthma and Immunology suggest montelukast as an effective adjuvant therapy in pregnant women for whom resistance to other asthma treatments, or decreased effectiveness of those treatments, has been established before pregnancy.10

In a published study on the safety of leukotriene receptor antagonists in pregnancy, the authors failed to detect any pattern of major malformations in the 72 infants exposed in utero to montelukast.11 In a Swedish registry study examining 129 montelukast-exposed cases, 3 of 7 malformed infants exposed to this drug had cardiac defects.12 Finally, a pregnancy registry maintained by the manufacturer of montelukast contains prospective reports of 185 live births, 7 of which had major congenital anomalies including limb defects.8

We prospectively followed up on 180 cases of montelukast exposure during pregnancy. Analysis of singleton outcomes among montelukast-exposed women resulted in a statistically lower mean (SD) birth weight of 3214.1 (656) g (P = .038) and shorter gestational age at birth (37.8 [3.1] weeks) compared with the nonteratogen-exposed group (P = .045) but not the disease-matched group (P = .891). Moreover, significantly higher rates of fetal distress at delivery (P = .007) were reported by montelukast-exposed women (25.6%) among the 3 groups. Montelukast-exposed infants were statistically different from the nonteratogen control group with respect to birth weight (P = .028) and rate of fetal distress (P = .010), while the disease-matched group differed from the nonteratogen-exposed women with respect to gestational age at birth (P = .046).13

Further subanalysis was conducted on those women who continued to use montelukast until the end of their pregnancies, and it is important to note that the only statistical difference that remained was found in the mean birth weight among the 3 groups (P = .032). Of the 143 infants exposed in utero during organogenesis, there was only 1 case of major malformation reported by a woman exposed to montelukast.13

Exposure to montelukast during pregnancy does not appear to increase the risk of major malformations above the 1% to 3% baseline in the general population. It is important that women are treated effectively for asthma during pregnancy to ensure the best outcome for the mothers.

View abstract >>

Competing interests
None declared

Can Fam Physician
Vol. 56, No. 9, September 2010, pp.881 - 882
Copyright © 2010 by The College of Family Physicians of Canada


  1. Kwon HL, Triche EW, Belanger K, Bracken MB. The epidemiology of asthma during pregnancy: prevalence, diagnosis, and symptoms. Immunol Allergy Clin North Am 2006;26(1):29–62. [Medline]
  2. Frezzo T, McMahon CL, Pergament E. Asthma and pregnancy. IL Teratogen Inf Serv 2002;9(2):1–5. Google Scholar
  3. Tamási L, Somoskövi A, Müller V, Bártfai Z, Acs N, Puhó E, et al. A population-based case-control study on the effect of bronchial asthma during pregnancy for congenital abnormalities of the offspring. J Asthma 2006;43(1):81–6. [Medline]
  4. Murphy VE, Clifton VL, Gibson PG. Asthma exacerbations during pregnancy: incidence and association with adverse pregnancy outcomes. Thorax 2006;61(2):169–76. [Abstract/Free  Full Text]
  5. Källén B, Rydhstroem H, Aberg A. Asthma during pregnancy—a population based study. Eur J Epidemiol 2000;16(2):167–71. [Medline]
  6. Alexander S, Dodds L, Armson BA. Perinatal outcomes in women with asthma during pregnancy. Obstet Gynecol 1998;92(3):435–40. [Medline]
  7. Källén B, Otterbald Olausson P. Use of anti-asthmatic drugs during pregnancy. 2. Infant characteristics excluding congenital malformations. Eur J Clin Pharmacol 2007;63(4):375–81. Epub 2007 Jan 30. [Medline]
  8. Merck & Co. Merck Research Laboratories seventh annual report on exposure during pregnancy from the Merck Pregnancy Registry for SINGULAIR (montelukast sodium) covering the period from U.S. approval (February 20, 1998) through May 22, 2006. West Point, PA: Merck Research Labs; 2008. Available from: www.merckpregnancyregistries.com. Accessed 2010 Jun 25.
  9. Gluck JC, Gluck PA. Asthma controller therapy during pregnancy. Am J Obstet Gynecol 2005;192(2):369–80. [Medline]
  10. American College of Obstetricians and Gynecologists, American College of Allergy, Asthma and Immunology. The use of newer asthma and allergy medications during pregnancy. Ann Allergy Asthma Immunol 2000;84(5):475–80. [Medline]
  11. Bakhireva LN, Jones KL, Schatz M, Klonoff-Cohen HS, Johnson D, Slymen DJ, et al. Safety of leukotriene receptor antagonists in pregnancy. J Allergy Clin Immunol 2007;119(3):618–25. [Medline]
  12. Källén B, Otterbald Olausson P. Use of anti-asthmatic drugs during pregnancy. 3. Congenital malformations in the infant. Eur J Clin Pharmacol 2007;63(4):383–8. Epub 2007 Feb 6. [Medline]
  13. Sarkar M, Koren G, Ying A, Kalra S, Smorlesi C, De Santis M, et al. Montelukast use during pregnancy: a multicentre, prospective, comparative study of infant outcomes. Eur J Clin Pharmacol 2009; Aug, Epub ahead of print. Google Scholar
Valid XHTML 1.0 Transitional [Valid RSS]

Motherisk is a proud affiliate of MotherToBaby, an information service of the non-profit Organization of Teratology Information Specialists (OTIS) across North America.

* - "MOTHERISK - Treating the mother - Protecting the unborn" is an official mark of The Hospital for Sick Children. All rights reserved.

The information on this website is not intended as a substitute for the advice and care of your doctor or other health-care provider. Always consult your doctor if you have any questions about exposures during pregnancy and before you take any medications.

Copyright © 1999-2018 The Hospital for Sick Children (SickKids). All rights reserved.

The Hospital for Sick Children (SickKids) is a health-care, teaching and research centre dedicated exclusively to children; affiliated with the University of Toronto. For general inquires please call: 416-813-1500.

  |  Contact SickKids  |  Terms of Use