title: Paternal age and preterm birth.
abstract: BACKGROUND
  There is growing evidence that advanced paternal age can be a reproductive hazard.
  
  
  METHODS
  We studied couples and their first children using nationwide registers in Denmark between 1980 and 1996. We restricted the analysis to mother's age 20-29 years. We estimated odds ratios (ORs) of preterm (< 37 weeks gestation) and very preterm birth (< 32 weeks) as a function of paternal age using logistic regression to adjust for potential confounding variables.
  
  
  RESULTS
  The risk of preterm birth increased with paternal age, almost entirely resulting from an association for very preterm birth. Compared with fathers age 20-24 years, ORs for very preterm birth were 1.3 (age 25-29), 1.4 (age 35-39), 1.7 (age 40-44), 1.6 (age 45-49), and 2.1 (age 50+) (test for trend: P = 0.01).
  
  
  CONCLUSIONS
  Risk of very preterm birth increases among older fathers, perhaps as a result of a paternal placental effect.
authors.affiliation: Danish Epidemiology Science Centre, University of Aarhus, Aarhus, Denmark.
authors.forename: Jin Liang
authors.initials: JL
authors.lastname: Zhu
authors.forename: Kreesten M
authors.initials: KM
authors.lastname: Madsen
authors.forename: Mogens
authors.initials: M
authors.lastname: Vestergaard
authors.forename: Olga
authors.initials: O
authors.lastname: Basso
authors.forename: Jørn
authors.initials: J
authors.lastname: Olsen
mesh_terms: D000328:Adult; D003718:Denmark / Q000453:epidemiology; D016021:Epidemiologic Studies; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D010331:Paternal Age; D047928:Premature Birth / Q000209:etiology*; D012042:Registries / Q000706:statistics & numerical data*; D012307:Risk Factors