title: Preterm Birth in the Context of Increasing Income Inequality.
abstract: OBJECTIVE
  Preterm birth is a leading cause of infant morbidity and mortality. Little is known about the contextual effect of U.S. income inequality on preterm birth, an issue of increasing concern given that the current economic divide is the largest since 1928.
  
  
  METHODS
  We examined changes in inequality over time in relation to preterm birth among singleton deliveries from an electronic medical record-based cohort (n = 223,512) conducted in 11 U.S. states and the District of Columbia from 2002 to 2008. Increasing income inequality was defined as a positive change in state-level Gini coefficient from the year prior to birth. Multi-level models estimated the independent effect of increasing inequality on preterm birth (>22 and <37 weeks) controlling for maternal demographics, health behaviors, insurance status, chronic medical conditions, and state-level poverty and unemployment during the year of birth.
  
  
  RESULTS
  The preterm birth rate was 12.3% where inequality increased and 10.9% where it did not. After adjustment, increasing inequality remained significantly associated with preterm birth (adjusted odds ratio 1.07, 95% confidence interval 1.04, 1.11). We observed no significant interaction by insurance status or race, suggesting that increasing inequality had a broad effect across the population.
  
  
  CONCLUSIONS
  The contextual effect of increasing income inequality on preterm birth risk merits further study.
authors.affiliation: Epidemiology Branch, Division of Population Health Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, 6100 Executive Blvd, Rockville, MD, 20852, USA.
authors.forename: Maeve E
authors.initials: ME
authors.lastname: Wallace
authors.affiliation: Epidemiology Branch, Division of Population Health Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, 6100 Executive Blvd, Rockville, MD, 20852, USA. Pauline.mendola@nih.gov.
authors.forename: Pauline
authors.initials: P
authors.lastname: Mendola
authors.affiliation: Biostatistics and Bioinformatics Branch, Division of Population Health Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, 6100 Executive Blvd, Rockville, MD, 20852, USA.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Chen
authors.affiliation: Biostatistics and Bioinformatics Branch, Division of Population Health Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, 6100 Executive Blvd, Rockville, MD, 20852, USA.
authors.forename: Beom Seuk
authors.initials: BS
authors.lastname: Hwang
authors.affiliation: Epidemiology Branch, Division of Population Health Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, 6100 Executive Blvd, Rockville, MD, 20852, USA.
authors.forename: Katherine L
authors.initials: KL
authors.lastname: Grantz
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D007223:Infant; D007226:Infant Mortality / Q000639:trends; D007231:Infant, Newborn; D011203:Poverty / Q000706:statistics & numerical data*; D011247:Pregnancy; D047928:Premature Birth / Q000453:epidemiology / Q000209:etiology*; D012307:Risk Factors; D012959:Socioeconomic Factors; D014481:United States / Q000453:epidemiology
keywords: Gini coefficient; Income inequality; Preterm birth