CONFERENCE PROCEEDING
Effect of smokefree policies on preterm birth: A systematic review and meta-analysis
1
Department of Primary Care and Public Health, School of Public Health, Imperial College London, London, United Kingdom
2
Department of Primary Care and Public Health, School of Public Health, Imperial College London, London, United Kingdom; Public Health Research Center, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
3
Nuffield Department of Primary Care Health Sciences, University of Oxford, Oxford, United Kingdom
4
Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam the Netherlands; Department of Neonatal and Paediatric Intensive Care, Erasmus MC Sophia Children’s Hospital, University Medical Center Rotterdam, Rotterdam, the Netherlands
Tob. Prev. Cessation 2026;12(Supplement 1):A166
ABSTRACT
BACKGROUND-AIM:
Second-hand smoke (SHS) exposure is a serious public health problem. SHS exposure causes around 1.2 million deaths a year, and women and children are often disproportionately affected. Around a third of female non-smokers and around 40% of children worldwide are regularly exposed to SHS. SHS exposure is a preventable cause of adverse birth outcomes, including preterm birth, which is a major risk factor for serious childhood illnesses and lifelong health disorders. Smokefree legislation reduces SHS exposure. Yet, around 40% of the world’s population is not covered by comprehensive smokefree policies. The aim of the systematic review is to assess the current available evidence on the effect of smokefree legislation on preterm birth.
METHODS:
A systematic review following PRISMA guidelines was conducted. Included studies evaluated multi-country, national, or regional smokefree legislations implemented across workplaces, public settings including outdoor settings, or both. The outcome of interest was preterm birth. We searched MEDLINE, Embase, and Web of Science, and included studies published from January 1, 2004, up to and including March 20, 2024. Two reviewers independently assessed all search results by title and abstract and by full text for eligibility. Randomised controlled trials and quasi-experimental studies could be included in the final review. Where available, adjusted percentage changes and 95% confidence intervals (CIs) were extracted as effect sizes. Otherwise, effect sizes were extracted and converted into percentage changes. Step changes (immediate risk changes) were pooled separately from slope changes (gradual risk changes). Relative risks were selected from the most adjusted model presented in each study and pooled using a DerSimonian-Laird random-effects meta-analysis. Risk of bias was assessed using a customised form adapted from the Cochrane Effective Practice and Organisation of Care (EPOC) criteria.
RESULTS:
A total of 16,402 unique citations were screened by title and abstract. We identified 20 eligible studies from: North America (10 studies); Europe (8 studies); Asia (1 study); and South America (1 study). Of the 20 studies, 12 had low and 8 had moderate risk of bias. The meta-analysis found that smokefree legislation was associated with a significant immediate reduction in preterm births of 2.18% (17 studies; approximately 2.8 million events; -2.18 [95% CI: -3.40 to -0.96]), and no additional significant gradual change in preterm births (2 studies; 78661 events; -0.01% [95% CI: -6.73 to 6.73]).
CONCLUSIONS:
Our findings fit within a much wider evidence base in support of smokefree legislation. Governments who have not implemented smokefree policies should be encouraged to legislate and enforce smokefree environments. For countries with existing smokefree policies, forward-looking policies such as banning smoking in cars with children present or promoting smokefree homes could be considered.
Second-hand smoke (SHS) exposure is a serious public health problem. SHS exposure causes around 1.2 million deaths a year, and women and children are often disproportionately affected. Around a third of female non-smokers and around 40% of children worldwide are regularly exposed to SHS. SHS exposure is a preventable cause of adverse birth outcomes, including preterm birth, which is a major risk factor for serious childhood illnesses and lifelong health disorders. Smokefree legislation reduces SHS exposure. Yet, around 40% of the world’s population is not covered by comprehensive smokefree policies. The aim of the systematic review is to assess the current available evidence on the effect of smokefree legislation on preterm birth.
METHODS:
A systematic review following PRISMA guidelines was conducted. Included studies evaluated multi-country, national, or regional smokefree legislations implemented across workplaces, public settings including outdoor settings, or both. The outcome of interest was preterm birth. We searched MEDLINE, Embase, and Web of Science, and included studies published from January 1, 2004, up to and including March 20, 2024. Two reviewers independently assessed all search results by title and abstract and by full text for eligibility. Randomised controlled trials and quasi-experimental studies could be included in the final review. Where available, adjusted percentage changes and 95% confidence intervals (CIs) were extracted as effect sizes. Otherwise, effect sizes were extracted and converted into percentage changes. Step changes (immediate risk changes) were pooled separately from slope changes (gradual risk changes). Relative risks were selected from the most adjusted model presented in each study and pooled using a DerSimonian-Laird random-effects meta-analysis. Risk of bias was assessed using a customised form adapted from the Cochrane Effective Practice and Organisation of Care (EPOC) criteria.
RESULTS:
A total of 16,402 unique citations were screened by title and abstract. We identified 20 eligible studies from: North America (10 studies); Europe (8 studies); Asia (1 study); and South America (1 study). Of the 20 studies, 12 had low and 8 had moderate risk of bias. The meta-analysis found that smokefree legislation was associated with a significant immediate reduction in preterm births of 2.18% (17 studies; approximately 2.8 million events; -2.18 [95% CI: -3.40 to -0.96]), and no additional significant gradual change in preterm births (2 studies; 78661 events; -0.01% [95% CI: -6.73 to 6.73]).
CONCLUSIONS:
Our findings fit within a much wider evidence base in support of smokefree legislation. Governments who have not implemented smokefree policies should be encouraged to legislate and enforce smokefree environments. For countries with existing smokefree policies, forward-looking policies such as banning smoking in cars with children present or promoting smokefree homes could be considered.
| eISSN: | 2459-3087 |
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