Changes in mortality for extremely low birth weight infants in the 1990s: implications for treatment decisions and resource use

Abstract

Objective: Much has changed in neonatal intensive care unit (NICU) care over the past decade. High-frequency oscillation, inhaled nitric oxide, and antenatal corticosteroids are now widely available. We wondered how these medical advances had affected both the epidemiology and ethics of life and death for extremely low birth weight (ELBW) infants in the NICU.

Methods: We identified 1142 ELBW infants (birth weight [BW] < 1000 g) consecutively admitted to our NICU between 1991 and 2001. We abstracted BW, gestational age, survival or death, and length of stay in the NICU. Statistical analyses were performed by using linear regression and 2-way analysis of variance.

Results: Both increasing BW and later year were significantly associated with improved survival. However, for larger ELBW infants, survival was approximately 90% for the entire decade, and large-scale improvement was hardly possible. For smaller infants, greater improvements were both possible and observed, at least early in the decade. From 1991 to 1997, overall ELBW survival increased steadily (approximately 4% per year). However, from 1997 to 2001, there was no significant improvement in survival for ELBW infants. There was no change in the distribution of deaths accounted for by BW subgroups within the ELBW population from 1991 to 2001. Median length of stay for infants who eventually expired before discharge rose from 2 days in 1991 to 10 days in 2001. As a consequence, during the past decade, the percentage of infants whose outcome was "undeclared" by day of life 4 rose from 10% to 20% for ELBW infants overall and to 33% for infants with BWs of 450 to 700 g. The percentage of ELBW NICU bed-days occupied by nonsurvivors remained very low (approximately 7%) from 1991 to 2001.

Conclusions: 1) Fewer infants in all ELBW subgroups are dying, compared with a decade ago, and the improvement has been most prominent for BWs of 450 to 700 g, at which mortality was and remains to be greatest. 2) This progress seems to have slowed, or even stopped, by the end of the decade. 3) Although most NICU nonsurvivors still expire early, doomed infants are lingering longer. 4) Nonsurvivors continue to occupy a constant (and extremely small) fraction of NICU bed-days.