Importance: Neonatal intensive care has been highly effective at improving newborn outcomes but is expensive and carries inherent risks. Existing studies of neonatal intensive care have focused on specific subsets of newborns and lack a population-based perspective.
Objectives: To describe admission rates to neonatal intensive care units (NICUs) for US newborns across the entire continuum of birth weight and how these rates have changed across time, as well as describe the characteristics of infants admitted to NICUs.
Design, setting, and participants: An epidemiologic time-trend analysis was conducted on April 1, 2015, of live births (≥500 g) from January 1, 2007, to December 31, 2012, to residents of 38 US states and the District of Columbia, recorded using the 2003 revision of the US Standard Certificate of Live Birth (N = 17,896,048).
Exposure: Birth year.
Main outcomes and measures: Crude, stratified (by birth weight), and adjusted admission rates. Trends in birth weight, gestational age, weight for gestational age, and use of assisted ventilation are presented to describe the cohort of admitted newborns.
Results: In 2012, there were 43.0 NICU admissions per 1000 normal-birth-weight infants (2500-3999 g), while the admission rate for very low-birth-weight infants (<1500 g) was 844.1 per 1000 live births. Overall, admission rates during the 6-year study period increased from 64.0 to 77.9 per 1000 live births (relative rate, 1.22; 95% CI, 1.21-1.22 [P < .001]). Admission rates increased for all birth weight categories. Trends in relative rates adjusted for maternal and newborn characteristics showed a similar 23% increase (95% CI, 1.22-1.23 [P < .001]). During the study period, newborns admitted to a NICU were larger and less premature, although no consistent trend was seen in weight for gestational age or the use of assisted ventilation.
Conclusions and relevance: After adjustment for infant and maternal risk factors, US newborns at all birth weights are increasingly likely to be admitted to a NICU, which raises the possibility of overuse of neonatal intensive care in some newborns. Further study is needed into the causes of the increased use observed in our study as well as its implications for payers, policymakers, families, and newborns.