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Objectives To assess the impact of comprehensive tobacco control policies on maternal smoking during pregnancy and perinatal outcomes over a 20-year period.Design Population-based cohort study using linked Scottish National Health Service. We assessed the impact of tobacco control measures on maternal smoking and perinatal outcomes over four distinct time periods. Step and slope changes in risk were evaluated using multivariable Poisson regression models with robust errors to determine immediate and sustained effects.Setting All Scottish National Health Service hospitals.Participants 919 324 singleton births between 24 +0 and 44+6 weeks gestation, spanning 1 January 2000 to 31 December 2019.Intervention Tobacco control policies were introduced progressively over four periods. Period A (2000–2002) served as the reference. Period B (2002–2006) introduced advertising restrictions, including bans on tobacco sponsorship and product displays. Period C (2006–2016) incorporated smoke-free legislation, prohibiting smoking in enclosed public spaces. Period D (2016–2019) introduced further legislative measures, bans on smoking in vehicles carrying children and enhanced taxation policies.Main outcome measures Maternal smoking, small for gestational age (SGA), stillbirth, preterm births and pre-eclampsia.Results Comprehensive measures were associated with a reduction in maternal smoking (step change relative risk (RR) A to D 0.73 (95% CI 0.70 to 0.75), which was sustained over time (slope RRA to D 0.97 (95% CI 0.95 to 0.99)). There were also reductions in pre-eclampsia (slope RRA to D 0.88 (95% CI 0.80 to 0.96), SGA (slope RRA to D 0.94 (95% CI 0.90 to 0.97). While preterm births increased (primarily iatrogenic), and stillbirth rates declined, these trends were not directly attributable to tobacco control measures.Conclusion Comprehensive tobacco control measures were associated with reduction in maternal smoking during pregnancy, pre-eclampsia and SGA, underscoring their potential to improve perinatal outcomes and supporting the global implementation of WHO-recommended tobacco-control strategies.