Fig. 2

Prevalence differences for county (left) and odds ratios for individual (right) analyses of preterm birth and environmental quality across rural–urban strata. Quintiles compared to lowest (“best environmental quality”) increasing from left to right. County-level analyses adjusted for race (proportion of minority residents), individual-level analyses adjusted for maternal race, education, age at delivery. Analyses of domain specific indices were adjusted for other domain indices (air for water, land, built, and sociodemographic). SD = Sociodemographic