Importance: As a result of consolidation in the health care delivery system, most very preterm infants in the US are born and receive care in multihospital health systems. The extent of variation in patient outcomes and length of stay for this vulnerable population across health systems and across hospitals within systems is not known.
Objective: To evaluate the extent of variation in mortality and length of stay within and across health systems for infants born very preterm (gestational age 24-29 weeks).
Design, setting, and participants: This cross-sectional study examined data contributed by Vermont Oxford Network US member hospitals in 224 health systems that delivered care to very preterm infants born between January 1, 2021, and December 31, 2022.
Exposure: Receipt of neonatal intensive care unit (NICU) care in a horizontally integrated multihospital health system.
Main outcomes and measures: Mortality rates and length of stay among surviving infants were estimated using multilevel logistic and linear models.
Results: The sample included 38 501 infants (median [IQR] gestational age, 27 [26-28] weeks; 52.8% boys). The median (IQR) number of infants receiving care at a hospital system during the 2-year period was 108 (59-198); 91.0% were born at the reporting hospital, and 95.4% were born in the reporting system. The mean adjusted mortality rate in the highest performing quartile of systems was 7.8% (95% credible interval [CrI], 7.3%-8.3%) compared with 9.8% (95% CrI, 9.1%-10.7%) for the lowest performing quartile. The mean adjusted length of stay for surviving infants ranged from 78 days (95% CrI, 77-79 days) to 90 days (95% CrI, 88-91 days) between the highest and lowest performing quartiles of systems, respectively.
Conclusions and relevance: In this cross-sectional study of very preterm infants, there was a 2-percentage point difference in mortality between systems in the highest and lowest performing quartiles and a 12-day difference in mean length of stay among surviving infants, which are potentially clinically meaningful. Opportunities exist for health systems to improve quality at the health system level to decrease mortality among infants born very preterm and reduce resources used in patient care.