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

Abstract

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.

PIP: Many previous studies have confirmed that maternal smoking during pregnancy results in decreased infant birthweight, but few such studies have analyzed the possible confounding effect of maternal alcohol consumption. To clarify this issue, birthweight data were obtained on 752 male and 739 female infants delivered at Finland's University Central Hospital of Turku in 1984-86. Smoking was found to explain less than 2% of the variation in birthweight of both sexes and alcohol less than 1% of the variation among female infants; alcohol consumption did not account for any of the variation in birthweight among male infants. When the data for male and female infants were analyzed separately, increasing gestational age and parity were both found to contribute to increased birthweight, although gestational age explained considerably more of the birth weight variation of male infants (24%) than female infants (14%). When regression coefficients were employed, maternal smoking was associated with a reduction in the birthweight of male and female infants of 20 grams/cigarette smoked/day. On the other hand, alcohol consumption was associated with a reduction of 90 grams in the birthweight of females and had no effect on this variable in males. The interaction of maternal smoking and alcohol consumption was not significant for either male or female birthweights. The most significant finding of this study is that only female fetuses seem to suffer from maternal alcohol consumption during pregnancy.