A study in Belgium that analyzed the effects of the reduction of smoking in public places showed that there was a significant reduction in the rates of preterm births.

During a four year period, after smoking was successively banned in public places, workplaces, restaurants and bars, rates of babies being born before 37 weeks dropped considerably.

The study has important health implications because previous evidence has linked premature birth to health complications such as chronic asthma.

Before the ban was implemented, the rate of premature births between the years 2002 and 2006 stood at about 1 percent.

The data showed that after smoking was banned restaurants in 200, rates of preterm births dropped 3.13 percent and after it was banned in bars serving food in 2010, rats dropped again by 2.65 percent per year.

The authors did note that the birth weights of babies did not change on average through the study period, indicating that there may be other factors at play.

"One could object that the effects of the smoking bans were apparent only on the rate of preterm births, and we acknowledge that the absence of an effect on birth weight and small for gestational age reduces the strength and diminishes the plausibility of our observation," the authors wrote.

From the paper:

What is already known on this topic:

  • Despite growing evidence that secondhand smoke has a negative impact on pregnancy duration and birth weight, few studies have shown a beneficial impact of smoke-free legislation on pregnancy outcomes

What this study adds:

  • Stepwise implementation of smoke-free legislation in Belgium allowed the demonstration of successive reductions in preterm deliveries which persisted after the implementation of the different legislation phases
  • The largest reductions in preterm birth coincided with the implementation of the second and the third phase of the legislation (smoking ban in restaurants and in bars serving food, respectively)
  • Even a small relative decline in preterm deliveries can have important public health benefits

If smoking bans are so beneficial to public health, why are they not implemented more widely around the world?

    The paper is published online at the British Medical Journal here.