Socioeconomic Disparities in Infant Health: An International Comparison
Method: This paper using the three national datasets: The Longitudinal Study of Australian Children – Birth Cohort (LSAC), the Millennium Cohort Study for the UK (MCS), and the Early Childhood Longitudinal Study – Birth Cohort and Fragile Families studies for the US (ECSL-B). The outcomes of interest include birthweight, low birthweight, and small for gestational age. The independent variables of interest are weighted income quintiles. A rich set of covariates are included in the models. The svy procedures in Stata SE 12 are used to adjust for sampling design in the calculation of weighted rates of low birthweight and logistic regression models (Odds Ratios).
Results: The results demonstrate clear SES gradients in low birthweight among infants in all three countries, where lower income is associated with higher rates of low birthweight births. The logistic regression models demonstrate that low and middle income women are significantly more likely to have a low birthweight infant in all three countries. However, in the fully adjusted logistic regression model, the graded relationship between income and low birthweight becomes attenuated. We find that the association between low income and low birthweight status is strongest in the US (OR=1.7) and Australia (OR=1.8), and lowest in the UK (OR=1.4). Associations in all three countries are statistically significant at p<.05.
Conclusion and Implications: Income inequality in low birthweight is as pervasive in Australia and the UK as it is in the US. Despite different social welfare and health care systems in Australia and the UK, infants born in these countries also experience health inequalities by income. This finding suggests support for societal inequality and relative social position as important factors driving SES inequalities in birth outcomes internationally, and social welfare policies that reduce inequality may benefit infant health.