Idiopathic preterm deliveries in Denmark.

Abstract

To characterize and quantify various demographic factors in idiopathic preterm delivery. 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. 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. Idiopathic preterm birth is more common in single, young women and is associated with a lower neonatal mortality rate than indicated preterm birth.