title: Idiopathic preterm deliveries in Denmark.
abstract: OBJECTIVE
  To characterize and quantify various demographic factors in idiopathic preterm delivery.
  
  
  METHODS
  All women with a permanent address in Denmark and a singleton pregnancy who gave birth to a preterm infant in 1982 (N = 51,851) were included. The material was obtained by a linkage of the Medical Birth Register and the National Register of Hospital Discharges, using personal identification numbers.
  
  
  RESULTS
  The incidence of singleton preterm delivery was 4.5% (N = 2330), of which 67% (N = 1557) were idiopathic. The neonatal mortality rate was significantly lower with idiopathic than with indicated preterm birth. Following stepwise logistic regression analysis, age under 20 (adjusted odds ratio [OR] 1.63, 95% confidence interval [CI] 1.07-2.47; P < .03), age above 30 (adjusted OR 0.74, 95% CI 0.60-0.90; P < .004) and being married (adjusted OR 0.63, 95% CI 0.43-0.94; P < .03) correlated with idiopathic preterm birth.
  
  
  CONCLUSIONS
  Idiopathic preterm birth is more common in single, young women and is associated with a lower neonatal mortality rate than indicated preterm birth.
authors.affiliation: Department of Obstetrics and Gynaecology, University Hospital (Rigshospitalet), Copenhagen, Denmark.
authors.forename: J
authors.initials: J
authors.lastname: Kristensen
authors.forename: J
authors.initials: J
authors.lastname: Langhoff-Roos
authors.forename: F B
authors.initials: FB
authors.lastname: Kristensen
mesh_terms: D000328:Adult; D016001:Confidence Intervals; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D007231:Infant, Newborn; D007236:Infant, Small for Gestational Age; D008423:Maternal Age; D007752:Obstetric Labor, Premature / Q000453:epidemiology* / Q000209:etiology; D016017:Odds Ratio; D011247:Pregnancy; D011256:Pregnancy Outcome / Q000453:epidemiology*; D012044:Regression Analysis; D014310:Triplets; D014427:Twins