Examining the Impact of Smokefree Laws on Preterm Birth

Introduction: Prenatal secondhand smoke exposure and smoking during pregnancy increase risk for preterm birth; however limited data exists on the impact of smoke-free communities on preterm birth (PTB). This paper describes the impact of smoke-free laws in Kentucky on low birth weight (LBW), PTB and smoking in the three months prior to pregnancy (PRIOR).

Methods: This study used Kentucky live birth certificate files from 2004 to 2009 in Kentucky counties/ cities with smoke-free laws/ordinances. Records were classified into pre-law and post-law based on at least one year prior to and after implementation, respectively with exclusion of implementation years. Laws with smoke-free enclosed public places were classified as strong (smoke-free enclosed public places) or weak (significant exemptions). Chi square analyses were completed to compare the births pre-and post-law. Multivariable logistic regressions were completed to relate LBW, PTB and PRIOR to ordinance timing, strength of law, and demographic explanatory variables.

Results: The sample included 75,234 records. Significant reductions in PTB and PRIOR were observed in communities post-law compared to pre-law (p <.0001). Births after implementation had reduced odds for PTB [Estimated Odds Ratio 0.87 (95% Confidence Interval 0.83-0.93)] and PRIOR [0.76 (0.73-0.79)]. Comprehensive strong laws also had reduced odds for PTB [0.94 (0.88-0.997) and PRIOR [0.94 (0.90-0.99) compared to weak laws when controlling for the other variables. No significant associations were identified for LBW.

Conclusion: Communities that adopt comprehensive smoke free laws can reduce PTB and PRIOR. These data may be used to guide tobacco policy development.