Effects of racial density and income incongruity on pregnancy outcomes in less segregated communities

A previous publication in this journal documented a decreased risk of adverse birth outcomes when African-American women have a positive income incongruity (defined as mothers living in a census tract with a higher household income than would be expected based on their individual education and marital status) and live in a census tract with “predominately African-American” residents [Pickett, K. E., Collins, J. W. Jr., Masi, C. M., & Wilkinson, R. G. (2005). The effects of racial density and income incongruity on pregnancy outcomes. Social Science & Medicine, 60(10), 2229–2238.]. The communities included in that study were from Chicago and were highly segregated by race. Our objective was to repeat this analysis in a less severely segregated environment: two urban counties (Wake and Durham) in central North Carolina. Rather than assuming an absence of knowledge about the effects of interest, we used the previously published results to inform our prior distributions in a Bayesian logistic regression analysis. This approach, which is analogous to a meta-analysis of the two studies, revealed a protective effect of positive income incongruity for African-American women living in census tracts with high relative African-American density across a much wider range of residential segregation patterns. Positive income incongruity was not associated with a decreased risk of low birth weight or preterm delivery for women living in tracts with a low relative density of African-Americans. These estimates are comparable to those that might have been observed had the original authors included a much more diverse set of communities with respect to degree of segregation, and so these new results provide important information about the generality of this intriguing finding.