The effect of moderate maternal alcohol consumption on birth weight and gestational age in a low risk population.

We analyzed the relationship between moderate maternal alcohol consumption during pregnancy and both birth weight corrected for gestational age and preterm delivery in 3447 women. Information on alcohol consumption in the first and second trimester was obtained during mid pregnancy and information about third trimester drinking was obtained a few days after delivery. After adjustment for possible confounders we found that for most women alcohol consumption was unrelated to birth weight corrected for gestational age and preterm delivery. However, in the subgroup of women smoking 20 cigarettes or more a day, drinking more than 120 g alcohol a week in early pregnancy was associated with a 7.2% (95% CI 0.2% to 14.2%) decrease in birth weight. We conclude that the effect of alcohol use on birth weight corrected for gestational age and gestational age is limited. However, in women who smoke heavily, a reported consumption of about two drinks or more a day in early pregnancy may be an additional risk factor for impaired fetal growth.