Close
Bianca De Stavola, London School of Hygiene & Tropical Medicine, Emily Grundy, London School of Economics and Political Science and Richard Silverwood, London School of Hygiene & Tropical Medicine
(Project no. 0301445, previously 30144)
The aim is to study the role of birthweight as a mediatory factor between social disadvantage and infant mortality. We will analyse live and still births to female LS members, maternal and paternal socio-economic characteristics (mainly taken from census data) and vital status of the infants by age 1 year.
This research is part of a research grant funded by ESRC: the whole project aims to identify pathways that link socio-demographic circumstances and biological disadvantage to adult health, and parental family and socio-economic circumstances to infant mortality, with a particular emphasis on the mediating factors that lie on these pathways.
This strand will use the ONS LS to study infant mortality and social disadvantage. Infant mortality is strongly patterned by socio-economic conditions, even in developed countries. It is also strongly and negatively related to birthweight, with the gradient seen even in babies born at term. This suggests that birthweight, itself strongly patterned by socioeconomic status, may act as a mediator in the pathway by which socio-economic disadvantage leads to increasing risk of infant death. However, there is also evidence that shows that the risks associated with low birthweight vary between population subgroups in apparently counter-intuitive ways. The most striking example of this comes from babies born to mothers who smoked during pregnancy. Such babies are usually around 100-200g lighter at birth than babies of non-smoking mothers, yet, for a given low birthweight, those exposed to maternal smoking are at lower risk of infant mortality than those unexposed. This "low birthweight paradox" has received much attention in the literature. Two broad alternative explanations have been offered. The first assumes that birthweight modifies the effect of disadvantage on infant mortality; the second that birthweight has no direct effect on infant mortality but shares a confounder with the outcome, i.e. that both birthweight and mortality risk are influenced by some other factor.
The ONS LS includes birthweight as recorded at birth registration for babies born to sample mothers and for LS members recruited to the study through birth. The outcome of interest is infant death. Indicators of social disadvantage include parental marital and family status, maternal age, and some information on parents' occupations. Births to LS sample mothers can be characterised by information on the mother (and other members of her household) collected in one or more preceding censuses, including indicators of education, occupation, employment, family and household structure, ethnicity and area of residence. Additionally, maternal age and parity can be used as both social and biological factors influencing birthweight and infant mortality; babies' gender and singleton status, and possibly season of birth, are also available and can be examined as potential confounders/modifiers. The main goal of this investigation is to study the mediatory role of birth weight.
No other UK study has access to individual information on all the variables relevant for this project (including birth weight, infant mortality and parental socio-economic circumstances) in sufficiently large numbers.