The study showed, for neonates born at a gestational age (GA) of 34 weeks or more, although inborn admission rates vary substantially across neonatal intensive care units (NICUs), the percentage of very ill admissions fails to explain this variation. The study was published in the JAMA Pediatrics

The authors wrote, "Our study of inborn NICU admissions for neonates born at a GA of 34 weeks or more found that this subpopulation accounts for 79.2% of all inborn NICU admissions and that reported inborn admission rates vary 34-fold across NICUs." "This wide variation is unexplained by the reported percentage of admissions with high illness acuity, comprising only 11.9% of inborn NICU admissions born at a GA of 34 weeks or more."

Although most newborns admitted to a NICU are born at 34 or more weeks of gestation, the degree of uniformity of admission criteria at this GA remains unclear. "This information gap matters because NICU care is costly, stressful, and entails risk of iatrogenesis," the authors emphasize. The authors therefore aimed to investigate how NICU inborn admission rates and percentage of high illness acuity admissions vary among these infants, and whether they are related.

The researchers performed a cross-sectional study of 358,453 live births at a GA of 34 weeks or more in California. Of these infants, 35,921 (10.0%) were admitted to a NICU, accounting for 79.2% of inborn NICU admissions at all GAs. Admission rates varied 34-fold, the authors say, ranging from 1.1% to 37.7% of births. However, high illness acuity accounted for only 4260 (11.9%) of these NICU admissions, and the percentage that met high illness acuity criteria varied 40-fold, ranging from 2.4% to 95.0%.

Although the researchers had expected that inborn admission rates would correlate positively with high illness acuity, they instead found that hospitals with higher NICU admission rates had a lower proportion of admitted newborns with high illness acuity (P < .001). In addition, although the authors cannot explain this negative correlation or the wide variation in NICU resource use, they note that the results of this study mirror those of other studies "that have raised concerns for supply-sensitive care."

"This troubling finding suggests that the illness acuity level for NICU admissions differs from one hospital to the next, raising the possibility that it is not adequately known which newborns will benefit from NICU care and/or that a great deal of NICU care is provided needlessly," they say. They note that, although statewide perinatal collaborative efforts have improved availability of newborn care data, the expansion of NICU care has outstripped these initiatives. Data deficiencies in the care and outcomes of newborns thus remain.

Although data deficiencies do not affect the findings of this study, the editorialists emphasize that such limitations prevent the researchers from highlighting the extent of the problem, the characteristics of affected newborns, or the consequences of the practice patterns.  Additional care and outcome measures are therefore needed for a wider set of births than exists today, Dr Goodman and Dr Little conclude.