Association between maternal smoking during pregnancy and recurrent wheezing in infancy: evidence from a meta-analysis

Background: Quantification of the association between the maternal smoking during pregnancy and recurrent wheezing in infancy is still conflicting. Thus, we performed a comprehensive meta-analysis to test the hypothesis that maternal smoking during pregnancy may increase the risk of recurrent wheezing in infancy. Methods: Pertinent studies were identified by a search in PubMed and Web of Knowledge up to October 2014. Random-effect model (REM) or fixed effects model (FEM) was used to combine study-specific results. Publication bias was estimated using Egger's regression asymmetry test. Results: Seven articles (3 cohort study and 4 cross-sectional studies) involving 8579 recurrent wheezing infant cases about maternal smoking during pregnancy and recurrent wheezing risk were used in this meta-analysis. The combined relative risks (RRs) of recurrent wheezing infants associated with maternal smoking during pregnancy was 1.491 (95% CIs = 1.329-1.672) overall. Significant associations were found both in Europe [RRs = 1.471, 95% CIs = 1.287-1.681] and other populations [RRs = 1.720, 95% CIs = 1.119-2.644] and cross-sectional studies [RRs = 1.474, 95% CIs = 1.306-1.663]. No publication bias was found. Conclusions: Our analysis indicated that maternal smoking during pregnancy could increase the risk of recurrent wheezing in infancy.