Purpose: The effects of moderate alcohol drinking on low birth weight are not clear, and conflicting results have been reported. We assessed the influence of different patterns of alcohol drinking during pregnancy on low birth weight.
Methods: A case-control study was carried out at the University of Cantabria Hospital, Spain, from 1998 to 2002. Cases (n = 552) were mothers delivering a single newborn weighing less than 2500 g. Controls (n = 1451) were selected from a random sample of all delivering women. Information was obtained from personal interview, clinical charts, and prenatal care records. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated. Adjustment for potential confounders was made by means of logistic regression.
Results: Alcohol consumption of less than 6 g/day decreased the risk for low birth weight (adjusted OR = 0.64; 95% CI, 0.46-0.88). A similar result was obtained for moderate drinkers (<12 g/day) on weekends only. The opposite relationship was observed between alcohol consumption on weekdays of 12 g/day or greater (adjusted OR = 2.67; 95% CI, 1.39-5.12), not observed in those drinking on weekends only. The interaction between alcohol consumption and tobacco smoking was analyzed. Weekday drinkers of 12 g/day or greater showed an increased risk in smokers. Alcohol consumption on weekends only in nonsmokers was inversely related. The influence of alcohol was greater for small-for-gestational-age (SGA) than non-SGA babies.
Conclusions: Alcohol consumption of 12 g/day or greater increased the risk for low birth weight, whereas lower consumption during weekends showed the opposite effect (mainly in nonsmokers).