Evaluating Epidemiologic Trends and Variations in NICU Admissions in California, 2008 to 2018.

Objective: Previous research suggests increasing numbers of and variation in NICU admissions. We explored whether these trends were reflected in California by examining NICU admissions and birth data in aggregate and among patient and hospital subpopulations more susceptible to variations in care.

Methods: In this retrospective cohort study, we evaluated NICU utilization between 2008 and 2018 for all live births at hospitals that provide data to the California Perinatal Quality Care Collaborative. We compared hospital- and admission-level data across birth weight (BW), gestational age (GA), and illness acuity categories. Trends were analyzed by using linear regression models.

Results: We identified 472 402 inborn NICU admissions and 3 960 441 live births across 144 hospitals. Yearly trends in NICU admissions remained stable among all births and higher acuity births (mean admission rates 11.9% and 4.1%, respectively). However, analysis of the higher acuity births revealed significant increases in NICU admission rates for neonates with higher BW and GA (BW ≥ 2500g: 1.8% in 2008, 2.1% in 2018; GA ≥ 37 weeks: 1.5% in 2010, 1.8% in 2018). Kaiser hospitals had a decreasing trend of NICU admissions compared to non-Kaiser hospitals (Kaiser: 13.9% in 2008, 10.1% in 2018; non-Kaiser: 11.3% in 2008, 12.3% in 2018).

Conclusions: Overall NICU admission rates in California were stable from 2008-2018. However, trends similar to national patterns emerged when stratified by infant GA, BW, and illness acuity as well as Kaiser or non-Kaiser hospitals, with increasing admission rates for infants born at higher BW and GA and within non-Kaiser hospitals.