Father's drinking and infant birth weight: report of an association.

Parents' drinking in the month prior to conception was ascertained for 377 infants born to members of a health maintenance organization. If the father had an average of two or more drinks daily, or had at least five drinks on one occasion, a decrease of 137 gm in infant birth weight was predicted, by means of regression analysis. This result was independent of maternal drinking, although infants whose mothers were regular drinkers weighed less at birth. The lower mean birth weights of infants of regular-drinking fathers was not due to parents' smoking, maternal use of caffeine, marijuana, or other drugs, or 21 other measured variables. This is the first report of an association in humans between father's drinking prior to conception and decreased infant birth weight. However, interpretation of this finding is difficult because the biological mechanisms that might underlie it are obscure.