Medical care and preterm infants of normal birth weight.

Preterm infants of normal birth weight (born before 37 completed weeks of gestation and weighing more than 2,250 g) experience a neonatal mortality risk almost four times higher than do term infants in the same weight range. In an analysis of the effect of hospital level of birth on neonatal mortality, such preterm normal weight infants were found to experience higher mortality if born outside of a Level 3 (tertiary care) center. For all singleton infants in this weight-gestation category born in New York City maternity services during a 3-year period (N = 23,257), the relative mortality risk for Level 1 births (compared with Level 3) was 1.72 (P less than .01) and for Level 2 births 1.47 (P less than .05). The excess mortality at Level 1 and Level 2 units was almost entirely due to a more than twofold higher death rate in black infants born in these units. Several potentially confounding socioeconomic, demographic, and biologic variables entered into a logistic regression model could not account for the higher mortality rates for black infants born in Level 1 and Level 2 units. Among black infants born at Level 1 units, deaths in preterm normal birth weight infants were less likely to occur in a receiving tertiary care center than were either deaths in low birth weight infants or deaths in term normal weight infants, suggesting that the need for special care of preterm normal birth weight infants is underestimated in some hospitals without newborn intensive care units.