title: The rise in singleton preterm births in the USA: the impact of labour induction.
abstract: OBJECTIVE
  To assess the extent to which increased rates of labour induction and caesarean section have contributed to the recent rise in preterm birth.
  
  
  METHODS
  National birth cohort study.
  
  
  METHODS
  USA.
  
  
  METHODS
  Singleton live births, with primary analysis based on non-Hispanic white women.
  
  
  METHODS
  Ecological study based on the 50 states and the District of Columbia during two time periods 10 years apart: 1992-94 and 2002-04.
  
  
  METHODS
  Preterm birth (live birth <37 completed weeks of gestation), based on an algorithm combining menstrual and clinical estimates of gestational age.
  
  
  RESULTS
  The state-level ecological analysis among non-Hispanic white women showed that the change in preterm birth rate from 1992-94 to 2002-04 was significantly associated with the change in rate of labour induction (r = 0.50, 95% CI 0.26-0.68), but not with the change in rate of caesarean delivery (r = -0.06, 95% CI -0.33 to 0.22). Weaker but otherwise similar associations with labour induction were observed in Hispanic women and in non-Hispanic black women.
  
  
  CONCLUSIONS
  Increasing use of labour induction is probably an important cause of the observed increased rate in preterm birth.
authors.affiliation: Department of Pediatrics, McGill University Faculty of Medicine, Montreal, QC, Canada.
authors.forename: X
authors.initials: X
authors.lastname: Zhang
authors.forename: M S
authors.initials: MS
authors.lastname: Kramer
mesh_terms: D000328:Adult; D000465:Algorithms; D002585:Cesarean Section / Q000009:adverse effects*; D015331:Cohort Studies; D005260:Female; D005865:Gestational Age; D006801:Humans; D007751:Labor, Induced / Q000009:adverse effects*; D011247:Pregnancy; D047928:Premature Birth / Q000453:epidemiology* / Q000209:etiology; D012307:Risk Factors; D014481:United States / Q000453:epidemiology; D044465:White People; D055815:Young Adult