PURPOSE OF THE STUDY.
To examine the association of maternal passive smoking during pregnancy and wheezing in children up to 2 years.
The authors of this study included 15 cohorts in the European project Environmental Health Risks in European Birth Cohorts. The cohorts were recruited from 1990 to 2008. A total of 37 459 mother-child pairs were available, and 27 993 had complete data on secondhand smoke exposure and wheeze.
Active and passive smoke exposure was obtained from questionnaire data submitted by each cohort. Four exposure definitions were created: prenatal active smoking, prenatal passive smoking, postnatal passive smoking, and unexposed. Eight exclusive exposure groups were created from these definitions. The primary outcome variable was any wheezing during the first 2 years of life by parental self-report. Other variables assessed included sex, family history of atopy, birth weight, gestational age, siblings, and parental education. Multilevel mixed-effects logistic regression was used to examine the effect of exposure to tobacco smoke on the development of wheeze. The model was adjusted for sex, family history of atopy, parental education, birth weight, gestational age, and siblings. Stratified analyses were performed for sex, family history of atopy, and geographic location of the cohorts. A meta-analysis was performed to take into account the heterogeneity between the cohorts.
Compared with the unexposed children, children with maternal prenatal passive exposure to smoking had an 11% increased risk of wheezing up to the age of 2 years (odds ratio [OR] 1.11; 95% confidence interval [CI] 1.03–1.20). Children with maternal prenatal passive smoking and postnatal passive smoking had a 29% increased risk of wheezing compared with unexposed children (OR 1.29; 95% CI 1.19–1.40). The most significant risk was found in children with active prenatal maternal smoking, passive prenatal maternal smoking, and postnatal passive smoking (OR 1.73; 95% CI 1.59–1.88). The risk of wheezing with smoke exposure was higher among children with a parental history of allergy.
Maternal passive prenatal smoke exposure is an independent risk factor for the development of wheeze in children up to the age of 2 years. The association was stronger in children with a family history of atopy.
The authors of this study expand our current understanding of exposure to tobacco smoke and the associated risk of wheeze in children. The authors assessed the type (active versus passive) and time frame (prenatal versus postnatal) of smoke exposure and evaluated the independent and combined effects of these variables. The risk of developing wheezing was highest in children exposed to active and passive smoking both prenatally and postnatally. These findings support the need to protect pregnant women and young children from passive smoke exposure and to further focus efforts on smoking cessation interventions for pregnant women and their partners.
- Copyright © 2017 by the American Academy of Pediatrics