Effect of a city-wide smoking ban on maternal smoking prevalence and risk of preterm and low birth weight births: The Colorado experience

Objectives: There exists a gap in the evidence regarding the association of maternal second hand smoke exposure and low birth weight (LBW) and preterm births. No data exist on the association of a public smoking ban on these fetal outcomes in the US. Methods: In this retrospective, observational study, we assessed maternal smoking prevalence and risk of LBW (< 2500g or <3000g) and preterm births (< 37 weeks gestation) in singleton births from mothers residing in Pueblo, Colorado (n=6,714) before (April 1, 2001 to July 1, 2003) and after (April 1, 2004 to July 1, 2006) a city-wide smoking-ban. During the incident time-period, these data were compared with another geographically isolated but proximal community, El Paso County, Colorado (n=32,281) with no such ordinance. Descriptive statistics and multivariable logistic regressions were used adjusting for multiple covariates. Results: Compared to El Paso, Pueblo experienced a 3% decline in maternal smoking (P=0.0002) and a 20% decline in preterm births (adjusted OR: 0.80, 95% CI: 0.662 - 0.983) pre and post smoking ban. The risk of LBW births declined by 12 % (adjusted OR: 0.88, 95% CI: 0.790 - 0.992) and 9% (adjusted OR: 0.91, 95% CI: 0.745 - 1.099) using the <2500g and < 3000g definitions for LBW, respectively. Conclusions: Our study results are the first to suggest an association between the institution of a smoking ban and a reduction in preterm but not LBW births. These data suggest the benefits of such smoking ordinances on fetal and maternal health.