title: Extreme maternal education and preterm birth: time-to-event analysis of age and nativity-dependent risks.
abstract: OBJECTIVE
  Increasing numbers of women achieve extremely high education, but the association with preterm birth (PTB) is poorly understood, especially over the life course. We sought to determine how very high educational attainment is associated with PTB, and to assess differences by maternal age and nativity.
  
  
  METHODS
  Data included singleton live births to mothers aged ≥ 20 years in metropolitan areas of Québec, Canada, from 1995 to 2005 (n = 537,525). Hazard ratios of PTB (<37 gestational weeks) were estimated over the continuous range of education (0-30 years) according to maternal age (20-24, 25-29, 30-34, ≥ 35 years) and nativity in a flexible survival model.
  
  
  RESULTS
  The relationship between education and PTB was not linear, but suggested that extremely high education was not as protective against PTB as slightly lower education. Education thresholds that offered maximum protection increased with maternal age, and were lower for Canadian-born (17-21 years of education) than foreign-born (22-25 years of education) mothers.
  
  
  CONCLUSIONS
  Extremely high education did not confer more protection against PTB than slightly lower education, and associations varied over the life course. The threshold number of years of education most protective against PTB: (1) increased with maternal age, especially for Canadian-born mothers, and (2) was higher for foreign-born mothers.
authors.affiliation: Institut National de Santé Publique du Québec, Montréal, Québec, Canada. nathalie.auger@inspq.qc.ca
authors.forename: Nathalie
authors.initials: N
authors.lastname: Auger
authors.forename: Michal
authors.initials: M
authors.lastname: Abrahamowicz
authors.forename: Alison L
authors.initials: AL
authors.lastname: Park
authors.forename: Willy
authors.initials: W
authors.lastname: Wynant
mesh_terms: D000328:Adult; D004522:Educational Status; D054242:Emigrants and Immigrants / Q000706:statistics & numerical data; D005260:Female; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D008423:Maternal Age; D009035:Mothers / Q000193:education*; D011247:Pregnancy; D011256:Pregnancy Outcome / Q000208:ethnology*; D047928:Premature Birth / Q000208:ethnology*; D016016:Proportional Hazards Models; D011792:Quebec / Q000453:epidemiology; D012307:Risk Factors; D012923:Social Class; D055815:Young Adult