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[Prematurity and low birth weight: effects of active and passive smoking during pregnancy].

Among the risk factors inevitably associated with low birthweights and premature births, tobacco remains the factor most often cited. From 1997 to 1998, a study was conducted in a Quebec City hospital centre in order to determine the prevalence of smoking among pregnant women as well as their exposure to passive smoking at home and at work. The percentage of women who smoke before pregnancy is 40.2%, while that of women who smoke during pregnancy is 37.3%. The analysis of characteristics of pregnant women who smoke and do not smoke shows strong variations according to age, education, matrimonial status and income. The relative risk linked to smoking is 1.54 for premature birth and 2.21 for low birthweight.