A broad smoking ban took effect in Scotland six years ago, and the change coincided with an improvement in medical statistics surrounding childbirth. Specifically, university researchers found a drop of more than 10 percent in the rate of premature births and more than 5 percent in the rate of low birth weight. The changes were large enough that they could not be explained by the decline in smoking that took place around the time of the smoking ban. The reduced exposure to cigarette smoke among nonsmokers is likely a larger part of the explanation.
Smoking bans have since taken effect in the rest of the United Kingdom and other countries. If similar results are found there, it will definitively link environmental cigarette smoke to premature births and low birth weight. Already it can be said that cigarette smoke is one of the major sources of short-term physical stress for nonsmokers.