title: Trends in preterm birth and perinatal mortality among singletons: United States, 1989 through 2000.
abstract: OBJECTIVE
  Despite the recent increase in preterm birth in the United States, trends in preterm birth subtypes have not been adequately examined. We examined trends in preterm birth among singletons following ruptured membranes, medical indications, and spontaneous preterm birth and evaluated the impact of these trends on perinatal mortality.
  
  
  METHODS
  A population-based, retrospective cohort study comprising 46,375,578 women (16% blacks) who delivered singleton births in the United States, 1989 through 2000, was performed. Rates of preterm birth (< 37 weeks), their subtypes, and associated perinatal mortality (stillbirths at >/= 22 weeks plus neonatal deaths within 28 days), before and after adjustment for potential confounders, were derived from ecological logistic regression models.
  
  
  RESULTS
  Preterm birth rates increased by 14% (95% confidence interval 13-15%) among whites from 8.3% to 9.4% and decreased by 15% (95% confidence interval 14-16%) among blacks from 18.5% to 16.2% between 1989 and 2000. Among whites, preterm birth following ruptured membranes declined by 23%, medically indicated preterm birth increased by 55%, and spontaneous preterm birth increased by 3%. Among blacks, preterm birth following ruptured membranes declined by 37%, medically indicated preterm birth increased by 32%, and spontaneous preterm birth decreased by 27%. The largest decline in perinatal mortality among whites was associated with increases in medically indicated preterm birth, whereas the largest decline in perinatal mortality among blacks was associated with declines in preterm birth following ruptured membranes and spontaneous preterm birth.
  
  
  CONCLUSIONS
  Temporal trends in preterm birth varied substantially based on underlying subtype and maternal race. The recent increase in medically indicated preterm birth was associated with a favorable reduction in perinatal mortality.
authors.affiliation: Division of Epidemiology and Biostatistics, Division of Maternal-Fetal Medicine, UMDNJ-Robert Wood Johnson Medical School, New Brunswick, New Jersey, USA. cande.ananth@umdnj.edu
authors.forename: Cande V
authors.initials: CV
authors.lastname: Ananth
authors.forename: K S
authors.initials: KS
authors.lastname: Joseph
authors.forename: Yinka
authors.initials: Y
authors.lastname: Oyelese
authors.forename: Kitaw
authors.initials: K
authors.lastname: Demissie
authors.forename: Anthony M
authors.initials: AM
authors.lastname: Vintzileos
mesh_terms: D000293:Adolescent; D000328:Adult; D001741:Black or African American / Q000706:statistics & numerical data; D015331:Cohort Studies; D016001:Confidence Intervals; D005260:Female; D006801:Humans; D015994:Incidence; D007226:Infant Mortality / Q000639:trends*; D007231:Infant, Newborn; D007234:Infant, Premature; D008423:Maternal Age; D010298:Parity; D011247:Pregnancy; D018566:Pregnancy, High-Risk; D047928:Premature Birth / Q000453:epidemiology* / Q000208:ethnology; D011336:Probability; D012042:Registries; D012189:Retrospective Studies; D018570:Risk Assessment; D014481:United States / Q000453:epidemiology; D044465:White People / Q000706:statistics & numerical data