[Is smoking during pregnancy a cause of premature delivery?].

Preterm birth is an important determinant of perinatal mortality and morbidity. During the last ten years the rate of preterm birth has remained unchanged, and even though advances in neonatal intensive care have improved the chances of survival of the preterm child, the mortality remains high. In most cases the etiology is unknown, but several factors have been associated with preterm birth. However, most of these factors are not accessible for prevention. The search for preventable causes of preterm birth is therefore important. We reviewed English publications concerning smoking during pregnancy and preterm birth. We conclude that smokers have about a 50% higher risk of preterm birth compared to non-smokers. Furthermore, a dose response relationship seems to be present; the more the pregnant women smoke the higher the risk of preterm birth. If all pregnant women stopped smoking it can be estimated that between 5% and 20% of all preterm births could be avoided.