Life course determinants of offspring size at birth: an intergenerational study of aberdeen women

Offspring size at birth is the result of a complex interplay of biological and social variables acting over several generations. However much current epidemiological research tends either to focus on measures of size at birth as initial explanatory variables in the pathway between early life and later adult health outcomes or it limits the context of the determinants of offspring size at birth to concurrently measured adult parental characteristics. This ignores the temporally distal influences on fetal growth, in particular the intergenerational influence of the maternal intrauterine environment. Integrating the distinct periods of influence on offspring size at birth requires a lifecourse approach that allows for the cumulative influence of both proximal and distal biological and social factors. The Aberdeen intergenerational cohort contains extensive parental, perinatal and developmental data on over 5000 females born between 1950 and 1955. Probabilistic record linkage to the Scottish Morbidity Record system linked 4000 females to over 7000 offspring delivery records. The linked intergenerational data were used to determine the effect of temporally ordered social and biological factors operating across a woman's lifecourse on her offspring's size at birth. The lifecourse approach suggested that socioeconomic inequalities seen in offspring size at birth were largely generated by continuity of social environments across generations and the effect of the early childhood social environment in particular on differential maternal lifetime growth. Most notably maternal intrauterine growth had an enduring intergenerational effect on offspring growth that was not diminished by later adult maternal or paternal, biological or social characteristics. Therefore interventions aimed at improving offspring size at birth on a population scale require intergenerational and lifecourse considerations, which acknowledge the long-term effect of the social environment, rather than just a short-term focus on the pre-pregnancy and pregnancy period.