Abstract
Background
Secondhand smoke exposure during pregnancy has long been associated with adverse health outcomes in children, but only a few studies have examined its effect modifiers. In this study, we applied effect modification analysis for maternal pre-pregnancy weight status on detrimental neurodevelopmental effect of secondhand smoke exposure during pregnancy and infancy in a nation-wide representative population.
Methods
Term singleton mother-infant pairs with non-smoking mothers were included for main analysis (N=15,987) from the Taiwan Birth Cohort Study (TBCS), and were further matched with propensity score (n=5,434). We extracted secondhand smoke exposure during pregnancy and infancy, and eight neurodevelopmental milestones from the responses in the baseline visit at six months, and eighteen months follow-up of TBCS. The associations between secondhand smoke exposure and neurodevelopmental achievement were analysed with multivariable logistic regression and Cox model. Propensity score weighting and matching were applied for high-versus-low analysis, and relative excess risk due to interaction were used to estimate effect modification.
Results
Higher secondhand smoke exposure was associated with increased likelihood of delayed milestone achievement across gross motor, fine motor, language-related and social-related domains. The associations in fine motor domains remained observable in propensity score weighted and matched models. We identified additive interaction with self-reported maternal overweight and obesity status before pregnancy in milestone development for walking with support, scribbling and waving goodbye.
Conclusion
Secondhand smoke exposure during pregnancy and infancy were associated with delayed neurodevelopmental milestone achievement at eighteen months, and the associations were modified by maternal pre-pregnancy overweight and obesity status.
Secondhand Smoke Exposure During Pregnancy and Mothers’ Subsequent Breastfeeding Outcomes: A Systematic Review and Meta-Analysis