Effects of maternal drinking, smoking, size, and parity on parent-offspring birth weight correlations.

Parent-offspring birth weight correlations are presented by sex of parent and infant. They range from .14 to .16, except for the mother-daughter correlation, which is .32. This pattern of parent-offspring correlations varies when the parity of the infant, the size of the mother, and the mother's drinking and smoking status are considered. All parent-offspring correlations are higher when the infant is parity 2 or more. The mother-daughter correlations are significantly higher than mother-son correlations when the mother is above average in usual weight, height, or pregnancy weight gain. When the mother smoked before conception, all birth weight correlations except mother-daughter are essentially zero. The mother-son correlation is also very small if the mother was a regular drinker, independent of her smoking status. The complex relationships in this sample demonstrate that interactions with environmental variables must be taken into account in studies of familial aggregation of human birth weight.