title: Maternal second-hand smoke exposure in pregnancy is associated with childhood asthma development.
abstract: BACKGROUND
  Childhood asthma development has been associated with active maternal smoking during pregnancy, but its association with maternal second-hand smoke exposure in pregnancy needs to be evaluated.
  
  
  OBJECTIVE
  We investigated longitudinal associations between maternal smoke exposure in pregnancy and childhood asthma development.
  
  
  METHODS
  In a population-based cohort of 5619 seven-year-old Toronto children, parents reported age of physician-diagnosed asthma development, maternal smoking during pregnancy, home second-hand smoke exposure from pregnancy until 7 years, demographics, and family history of atopy. By using Cox proportional and discrete-time hazard survival analyses, we evaluated associations between asthma and maternal smoking or home second-hand smoke exposure in pregnancy.
  
  
  RESULTS
  During pregnancy, 5.0% of mothers smoked and 6.2% were nonsmokers and exposed to home second-hand smoke; 15.5% of children developed asthma. Children whose mothers smoked or were exposed to home second-hand smoke during pregnancy were more likely to develop asthma (adjusted hazard ratio [HR] 1.30 [95% CI, 1.06-1.60]). The association persisted for children of nonsmoking mothers with home second-hand smoke exposure during pregnancy (adjusted HR 1.34 [95% CI, 1.01-1.76]), children with asthma symptoms in the past year (adjusted HR 1.36 [95% CI, 1.03-1.79]), and after adjusting for home second-hand smoke exposure from birth to age 7 years.
  
  
  CONCLUSIONS
  Maternal home second-hand smoke exposure during pregnancy is associated with incident physician-diagnosed childhood asthma, even if the mother does not smoke actively during pregnancy. Childhood asthma prevention programs should include smoking cessation strategies targeted toward smokers who live in the homes of smoking and nonsmoking pregnant women as well as pregnant women who smoke.
authors.affiliation: Clinical Epidemiology and Health Services Research, University of Toronto, Ontario, Canada; Child Health Evaluative Sciences, Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Elinor
authors.initials: E
authors.lastname: Simons
authors.affiliation: Child Health Evaluative Sciences, Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Teresa
authors.initials: T
authors.lastname: To
authors.affiliation: Department of Family and Community Medicine, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Rahim
authors.initials: R
authors.lastname: Moineddin
authors.affiliation: Air Quality Health Effects Research Section, Health Canada, Ottawa, Ontario, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Stieb
authors.affiliation: Child Health Evaluative Sciences, Hospital for Sick Children, Toronto, Ontario, Canada; Division of Respiratory Medicine, Hospital for Sick Children, Toronto, Ontario, Canada. Electronic address: sharon.dell@sickkids.ca.
authors.forename: Sharon D
authors.initials: SD
authors.lastname: Dell
mesh_terms: D001249:Asthma / Q000209:etiology*; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D018811:Maternal Exposure / Q000009:adverse effects*; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D014028:Tobacco Smoke Pollution / Q000009:adverse effects*
chemical_list: D014028:Tobacco Smoke Pollution
keywords: Asthma; Breastfeeding; Children; Incident asthma; Income adequacy; Maternal asthma; Physician-diagnosed asthma; Pregnancy; Second-hand smoke