Association between prenatal environmental tobacco smoke exposure and preterm birth: A systematic review and meta‐analysis

Abstract Introduction The purpose of this systematic review and meta‐analysis is to evaluate the global risk of preterm birth associated with passive smoking. Specifically, the study aims to examine whether passive smoking continues to impact preterm birth rates, with particular attention to the potential effects following the implementation of stricter smoking bans in recent years. Material and Methods This systematic review and meta‐analysis followed PRISMA guidelines and was preregistered in PROSPERO. A comprehensive literature search was conducted in PubMed, Embase, CINAHL, and Web of Science up to February 17, 2024, using keywords related to passive smoking and preterm birth. Eligible observational studies were selected, and data were independently extracted and assessed for quality by two authors. Statistical analysis used odds ratios (ORs) and the I 2 statistic for heterogeneity. Subgroup analyses and publication bias assessments were conducted. Review Manager and Stata were used for the analysis, with significance set at p  < 0.05. Results Meta‐analysis showed a 21% increase in the odds of preterm birth in women exposed to environmental tobacco smoke (ETS) (OR, 1.21; 95% CI, 1.10–1.32) with significant heterogeneity ( I 2  = 76.2%). Stronger associations were found in cohort and cross‐sectional studies, studies in Asia, larger sample sizes, and recent publications. Findings were robust across various analyses. Conclusions Prenatal environmental tobacco smoke exposure significantly increases preterm birth risk. Effective public health interventions, including stringent smoke‐free policies, public education, and awareness campaigns, are needed to reduce environmental tobacco smoke exposure and improve maternal and infant health outcomes.