We ascertained outcomes of all live births <1500 g in two prospective inception cohorts. We estimated mortality risk from birth weight and illness severity on admission and measured therapeutic intensity. We calculated logistic regression models to estimate the changing odds of mortality between cohorts.Results
Neonatal intensive care unit mortality declined from 17.1% to 9.5%, and total mortality declined from 31.6% to 18.4%. Cohort 2 had lower risk (higher birth weight, gestational age, and Apgar scores and lower admission illness severity for newborns [greater-than or equal to]750 g). Risk-adjusted mortality declined (odds ratio, 0.52; confidence interval, 0.29-0.96). One third of the decline was attributable to "better babies" and two thirds to "better care." Use of surfactant, mechanical ventilation, and pressors became more aggressive, but decreases in monitoring, procedures, and transfusions resulted in little change in therapeutic intensity.Conclusions
Mortality decreased nearly 50% for infants <1500 g in 5 years. One third of this decline is attributable to improved condition on admission that reflects improving obstetric and delivery room care. Two thirds of the decline is attributable to more effective newborn intensive care, which was associated with greater aggressiveness of respiratory and cardiovascular treatments. Attribution of improved birth weight specific mortality solely to neonatal intensive care may underestimate the contribution of high-risk obstetric care in providing "better babies." Pediatrics 1998;102:893-899.