Maternal exposure to second-hand smoke during pregnancy and risk of autism spectrum disorder in offspring: A systematic review and meta-analysis.
BackgroundEmerging evidence suggests that environmental exposures during pregnancy may influence the risk of autism spectrum disorder (ASD) in offspring. Maternal exposure to second-hand smoke is a potentially modifiable risk factor, but previous studies have reported inconsistent findings. This is the first meta-analysis on the association between maternal second-hand smoke exposure during pregnancy and the risk of ASD in children.Materials and methodsA systematic search of the PubMed, Web of Science, and Scopus databases was conducted, covering articles published up to May 2, 2026, without language or publication date restrictions. Observational studies reporting odds ratios (ORs) for the association between maternal passive smoking during pregnancy and ASD diagnosis in offspring were included. Methodological quality was assessed using the Newcastle-Ottawa Scale. A random-effects model was used to calculate pooled ORs. Subgroup analysis was performed based on study design, and publication bias was evaluated using Begg's and Egger's tests.ResultsNine studies comprising 9,005 participants met the inclusion criteria. The pooled OR from adjusted studies demonstrated a statistically significant association between maternal second-hand smoke exposure during pregnancy and ASD risk (OR = 2.12; 95% CI: 1.59-2.66), indicating that exposed children had more than twice the risk of ASD compared to unexposed children.ConclusionsMaternal exposure to second-hand smoke during pregnancy was associated with increased odds of ASD in offspring. The findings highlight the importance of public health interventions aimed at reducing prenatal second-hand smoke exposure, including smoke-free legislation and smoking cessation counseling for pregnant women and their families.