Birth weight and income: interactions across generations.

This paper attempts to answer a series of questions regarding the interaction of income and birth weight across generations. First, does the effect of the income of a mother during her pregnancy on her infant's birth weight depend on the family's birth weight history (genetic predisposition)? Second, does the effect of low birth weight status on adult life chances depend on income during early childhood? These questions have implications for the way we envision the biological and social worlds as interacting across generations. To address these issues, this study uses intergenerational data from the Panel Study of Income Dynamics, survey years 1968 through 1992. Results of sibling comparisons (family-fixed-effects models) demonstrate that maternal income has a significant impact on birth weight for those infants who are already at high risk hereditarily (i.e., who have a low birth weight parent). However, it is not clear whether income acts as a developmental buffer for low birth weight infants as their lives progress. These findings suggest the existence of biosocial interactions between hereditary predisposition and socio-economic environment.