Objectives: This multisite study sought to identify (1) any differences in admission risk (defined by gestational age and illness severity) among neonatal intensive care units (NICUs) and (2) obstetric antecedents of newborn illness severity.
Methods: Data on 1476 babies born at a gestational age of less than 32 weeks in 6 perinatal centers were abstracted prospectively. Newborn illness severity was measured with the Score for Neonatal Acute Physiology. Regression models were constructed to predict scores as a function of perinatal risk factors.
Results: The sites differed by several obstetric case-mix characteristics. Of these, only gestational age, small for gestational age. White race, and severe congenital anomalies were associated with higher scores. Antenatal corticosteroids, low Apgar scores, and neonatal hypothermia also affected illness severity. At 2 sites, higher mean severity could not be explained by case mix.
Conclusions: Obstetric events and perinatal practices affect newborn illness severity. These risk factors differ among perinatal centers and are associated with elevated illness severity at some sites. Outcomes of NICU care may be affected by antecedent events and perinatal practices.