Maternal smoking and alcohol consumption as determinants of birth weight in an unselected study population.

A prospective study was conducted to determine the effects of maternal smoking and alcohol consumption during pregnancy on the birth weight of fetuses in an unselected study population. Several confounding factors were taken into account. The main factors associated with an increase of birth weight of both sexes were gestational age at birth and parity. Both maternal smoking and maternal alcohol consumption during pregnancy had the effect of decreasing the birth weight of female fetuses, whereas smoking, but not alcohol, had a decreasing effect on birth weight of male and female fetuses.