IDIOPATHIC PRETERM DELIVERIES IN DENMARK

Objective: To characterize and quantify various demographic factors in idiopathic preterm delivery. Methods: All women with a permanent addr ess in Denmark and a singleton pregnancy who gave birth to a preterm i nfant 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: T he incidence of singleton preterm delivery was 4.5% (N = 2330), of whi ch 67% (N = 1557) were idiopathic. The neonatal mortality rate was sig nificantly lower with idiopathic than with indicated preterm birth. Fo llowing 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 bein g married (adjusted OR 0.63, 95% CI 0.43-0.94; P < .03) correlated wit h idiopathic preterm birth. Conclusion: Idiopathic preterm birth is mo re common in single, young women and is associated with a lower neonat al mortality rate than indicated preterm birth.