Effect of Smoke-Free Legislation on Perinatal and Child Health

Abstract

Smoking kills approximately 5.7 million people each year. Although smoke-free legislation and tobacco controls are keys to reducing this death toll, most studies on their effectiveness have involved only adults. Children are known to be especially vulnerable to the adverse effects of second-hand smoke, which has been linked to many adverse outcomes during early life and the development of noncommunicable diseases in later life. This review was conducted to evaluate the effect of smoke-free legislation on perinatal and child health. The search included online databases for studies published from January 1975 to May 2013. Eligible studies investigated the association between introduction of a smoking ban in work or public places and one or more prespecified health outcomes in children. The study included children 12 years or younger to minimize potential confounding by self-smoking but accepted ages up to 20 years if most of the population met the original age criterion. Primary outcomes were preterm birth, low birth weight, and asthma. Secondary outcomes included various perinatal mortality indicators. Parental or maternal smoking was defined as the main confounder for which adjustment was recorded. Of 9228 screened titles, 20 potentially eligible studies were found and 11, reported between 2008 and 2013, were included in the analysis. Four studies described the effect on pediatric asthma; all others reported on perinatal outcomes. Three of 5 studies reported a significant reduction in preterm births after introduction of smoke-free legislation. Meta-analysis of 4 studies showed that smoke-free legislation was associated with a clinically important and statistically significant drop in preterm birth (1,366,862 participants; 10.4%; 95% confidence interval [CI], 18.8 to 2.0) with no later effect on preterm birth rate change over time. One of 6 studies reported a reduction in neonates with low birth weight (<2500 g) after smoke-free legislation. Three of 4 studies reported a significant drop in hospital attendance because of asthma after introduction of legislation. An immediate reduction was reported in 3 studies (225,753 events; 10.1%; 95% CI, 15.2 to 5.0), and an additional nonsignificant trend toward an annual rate decrease was reported in 3 studies (241,846 events; 7.5% per year; 95% CI, 16.0 to 0.9). One study reported a reduction in very preterm birth, and 1 of 2 studies found a significant effect on the rate of neonates with very low birth weight (<1500 g). Two of 3 studies showed a significant step reduction in small for gestational age. These reductions were statistically significant after pooling (1,305,965 participants; step change: 5.3%; 95% CI, 5.4 to 5.2; slope change: 0.6%; 95% CI, 0.604% to 0.596%). In a small study, no effect was noted on birth defects. This study provides evidence supporting the effectiveness of smoke-free legislation to improve perinatal and child health outcomes. Rates of preterm birth and pediatric hospital admissions for asthma were reduced by 10% along with reductions in the risk for being born very small for gestational age. The results support mandates for worldwide implementation of smoke-free legislation to improve population health. Early-life protection from involuntary second-hand smoke exposure has the potential to reduce disease burdens and associated economic losses in society.