Objective: To elucidate the role of level of care in combination with other perinatal risk factors for infant death in very preterm deliveries.
Design: Population-based cohort study.
Setting: Sweden, 1992-1998.
Subjects: Singleton infants (2285) born at 24 to 31 completed weeks of gestation to primiparous women.
Main outcome measure: Infant mortality.
Results: The rate of infant mortality increased from 5% among infants born at 31 weeks' gestation to 56% among infants born at 24 weeks' gestation. Compared with infants born at university hospitals, the unadjusted odds ratio (OR) of infant death was 0.70 (95% confidence interval [CI]: 0.54-0.90) among infants delivered at general hospitals. However, after adjustment, the OR of infant death shifted to 1.33 (95% CI: 0.88-2.02) for preterm births at general hospitals. This shift was primarily due to different gestational age distributions in regional and general hospitals. Among infants born at 24 to 27 weeks' gestation, infant mortality rates were 23% (87 deaths) in university hospitals and 32% (73 deaths) in general hospitals, giving an adjusted OR of 2.00 for general versus university hospitals (95% CI: 1.15-3.49). The risk of death at 24 to 27 weeks' gestation in general hospitals was increased specifically in pregnancies with placental complications.
Conclusion: Taking obstetric complications into account, there is an excess mortality risk among extremely preterm infants born at general hospitals.