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Allergy, Asthma & Clinical Immunology

Open Access

Associations between second-hand smoke exposure in pregnancy and age of childhood asthma development

  • Elinor Simons1, 2Email author,
  • Teresa To1,
  • Rahim Moineddin3,
  • David Stieb4 and
  • Sharon Dell1, 2
Allergy, Asthma & Clinical Immunology20128(Suppl 1):A4

Published: 2 November 2012


AsthmaSmoking CessationChildhood AsthmaMaternal SmokingAdjust Hazard Ratio


Maternal smoking during pregnancy has been associated with an increased hazard of incident childhood asthma. We investigated the association between any second-hand smoke exposure in early life and childhood asthma development.


In the Toronto Child Health Evaluation Questionnaire, parents of 5619 grades 1-2 students reported age of physician-diagnosed asthma development, exposure to maternal and household second-hand smoke during pregnancy and the first year of life, socio-demographic factors, and other early-life exposures such as mold and cockroach. Using Cox proportional hazard models, we evaluated the longitudinal associations between second-hand smoke exposure and age of asthma development.


Household second-hand smoke exposure prevalence was 8.3% during pregnancy and 10.6% in the first year of life; 15.5% of children developed asthma. After adjusting for sex, prematurity, being born in Canada and maternal asthma, children exposed to home second-hand smoke during pregnancy were more likely to develop asthma and developed asthma sooner [adjusted hazard ratio (HR) 1.36, 95% confidence interval (CI): 1.09, 1.70], even after excluding children whose mothers smoked in pregnancy (HR 1.53, 95% CI: 1.09, 2.14). The association strengthened (HR 1.88, 95% CI: 1.16, 3.02) after adjusting for home second-hand smoke exposure in the first year.


Home second-hand smoke exposure during pregnancy is associated with an increased hazard of childhood asthma development, even if the mother is not a smoker. Recommendations for smoking cessation during pregnancy should focus on pregnant women and members of their households.

Authors’ Affiliations

The Hospital for Sick Children, Child Health Evaluative Sciences, Toronto, Canada
The Hospital for Sick Children, Division of Respiratory Medicine, Toronto, Canada
The University of Toronto, Department of Family and Community Medicine, Toronto, Canada
Health Canada, Ottawa, Canada


© Simons et al; licensee BioMed Central Ltd. 2012

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.