DECLINING SEVERITY ADJUSTED MORTALITY - EVIDENCE OF IMPROVING NEONATAL INTENSIVE-CARE

Objectives. Declines in neonatal mortality have been attributed to neo natal intensive care. An alternative to the ''better care'' hypothesis is the ''better babies'' hypothesis; ie, very low birth weight infant s are delivered less ill and therefore have better survival. Design. W e ascertained outcomes of all li ve births <1500 g in two prospective inception cohorts. We estimated mortality risk from birth weight and i llness severity on admission and measured therapeutic intensity. We ca lculated logistic regression models to estimate the changing odds of m ortality between cohorts. Patients and Setting. Two cohorts in the sam e two hospitals, 5 years apart (1989-1990 and 1994-1995) (total n = 73 9). 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 equ al to 750 g). Risk-adjusted mortality declined (odds ratio, 0.52; conf idence interval, 0.29-0.96). One third of the decline was attributable to ''better babies'' and two thirds to ''better care.'' Use of surfac tant, mechanical ventilation, and pressors became more aggressive, but decreases in monitoring, procedures, and transfusions resulted in lit tle change in therapeutic intensity. Conclusions. Mortality decreased nearly 50% for infants <1500 g in 5 years. One third of this decline i s attributable to improved condition on admission that reflects improv ing obstetric and delivery room care. Two thirds of the decline is att ributable to more effective newborn intensive care, which was associat ed with greater aggressiveness of respiratory and cardiovascular treat ments. 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.''