Socio-economic status and z-score standardized height-for-age of U.S.-born children (ages 2-6).

This study explores socio-economic gradients in height (stature-for-age) among a nationally representative sample of 2-6 year old children in the United States. We use NHANES III (1988-1994) Youth data linked with a special Natality Data supplement which contains information from birth certificates among sampled NHANES III Youth who are < 7 years of age. Our results indicate significant socio-economic gradients for both maternal education and family income, net of controls for confounders, including: birth weight, gestational age, family size, and parental heights. These results are in stark contrast to those from other developed countries that seem to indicate diminished or eliminated socio-economic disparities, net of known confounders. In the United States, it appears that socio-economic gradients have an effect on birth outcomes, and continue to have an additional direct and independent effect on height, even in early childhood.