OBJECTIVES. The objectives of this study were to describe the characteristics and morbidity of very low birth weight infants, to identify the medical intervention for these infants, and to evaluate the factors affecting the mortality of these infants among the participating hospitals.

METHODS. A large multicenter neonatal research network that included level III NICUs from throughout Japan was established. A standardized mortality rate was formulated by giving a ratio of the observed deaths and the predicted deaths based on a 100-g birth weight interval mortality. A regression model was used to predict the factors that affect neonatal mortality.

RESULTS. The network included 37 centers and 2145 infants weighing ≤1500 g, born or admitted to the centers in 2003. Gestational age and birth weight of studied infants were 28.6 ± 3.6 gestational weeks (mean ± SD) and 1025 ± 302 g, respectively. Overall, 11% of the infants died before being discharged from hospitals (range: 0%–21%). The standardized mortality rate varied among the facilities (range: 0%–30%). No association between the annual number of patients admitted and standardized mortality rate was found. Among all of the very low birth weight infants, 14% were outborn infants, 72% were delivered by cesarean sections, 27% had patent ductus arteriosus, 3% had gastrointestinal perforation, 8% had bacterial sepsis, and 13% had intraventricular hemorrhage. Medical interventions involved were: 41% antenatal corticosteroids, 54% surfactant therapy, 18% postnatal steroids for chronic lung disease, and 29% high-frequency oscillatory ventilation. We found variations in the medical interventions and the clinical outcomes among the centers.

CONCLUSIONS. The overall survival rate for very low birth weight infants among neonatal centers in Japan was ∼90%. However, differences in the morbidity and mortality were observed among these centers.

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