Introduction It is well known that maternal smoking during pregnancy results in adverse reproductive outcomes. However, the impact of passive smoking on fetal growth is less clear. The aim of this study was to determine the socioeconomic status of pregnant women who were exposed to tobacco smoke and its influence on birth weight of their newborns.

Methods This descriptive study was conducted on 450 nonsmoker women with singleton live births. Data on demographic, social and reproductive characteristics were obtained. Women were asked for details of their exposure to smoking at home or in the workplace. Data were analysed using χ², independent t-test, ANOVA and Regression methods.

Results One hundred seventy seven women (39.3%) were exposed to tobacco smoke. A significant association between passive smoking and socioeconomic indices such as the educational level and the occupation of the women and their spouses was found. The proportion of passive smokers was lower in families with higher income. Infants born to passive smokers weighed a mean of 28 g lighter than those born to non-passive smokers (p=0.53). The mean birth weight of infants born to women whose husbands smoked more than 10 cigarettes per day was 3.110 kg, resulting in a greater difference of 49 g.

Conclusion The results provide no significant decrease in birth weight of infants born to passive smokers in comparison with non-passive smokers, which may be related to a lower extent of exposure in this population.