Are racial disparities in preterm birth larger in hypersegregated areas?

The causes of the racial/ethnic disparity in preterm birth (PTB) remain largely unknown; traditional risk factors such as smoking and prenatal care fail to account for it. The authors examined whether living in metropolitan areas (MAs) with high levels of residential racial segregation along multiple dimensions (hypersegregation) was associated with higher rates of PTB or larger racial disparities in PTB and whether segregation modified the established race-age association in PTB. The authors merged 2000 natality data (n = 1,944,703) with US Census measures of Black-White hypersegregation. They executed two-level hierarchical logistic regression analyses among White and Black mothers in 237 MAs to estimate the odds of PTB by hypersegregation, race, and age, after controlling for covariates. In unadjusted and adjusted models, Black infants in hypersegregated MAs were more likely to be preterm than Black infants in nonhypersegregated MAs (p < 0.001). Black-White PTB disparities were larger in hypersegregated areas than in nonhypersegregated areas (p < 0.001), and the age-race association with PTB was modified by hypersegregation (p < 0.001). Living in a hypersegregated MA had a more pronounced association with PTB among older Black women, and racial disparities in PTB were larger in hypersegregated areas among older mothers (p < 0.001). Since over 40% of Black childbearing women live in hypersegregated areas, residential segregation may be an important social determinant of racial birth disparities.