Mehra R, et al. - In this retrospective cohort study, researchers used national, commercial health insurance claims data from 2011, obtained from the Health Care Cost Institute, to examine the link between area-level deprivation and preterm birth, and to assess mediation by maternal medical, behavioural, and psychosocial factors. They used ZIP code-level data to determine area-level deprivation and mediating effects were determined by using multilevel structural equation modeling. Overall, 138,487 women with a live singleton birth were included. These women were residing in 14,577 ZIP codes throughout the United States. An increased risk of preterm birth was observed in association with area-level deprivation even among commercially-insured women. No threshold effect of area-level deprivation was noted, similar to individual socioeconomic status. A lower risk of preterm birth could be related to the implementation of policies to attenuate area-level deprivation, and the screening and treatment of maternal mediators.