Variability of Very Low Birth Weight Infant Outcome and Practice in Swiss and US Neonatal Units.

Objectives: Outcomes of very preterm infants vary considerably between health care facilities. Our objective was to compare outcome and practices between the Swiss Neonatal Network (SNN) and US members of the Vermont Oxford Network (US-VON).

Methods: Retrospective observational study including all live-born infants with a birth weight between 501 and 1500 g as registered by SNN and US-VON between 2012 and 2014. We performed multivariable and propensity score-matched analyses of neonatal outcome by adjusting for case-mix, race, prenatal care, and unit-level factors, and compared indirectly standardized practices.

Results: A total of 123 689 infants were born alive in 696 US-VON units and 2209 infants were born alive in 13 SNN units. Adjusted risk ratios (aRRs) for the composite "death or major morbidity" (aRR: 0.56, 95% confidence interval: 0.51-0.62) and all other outcomes were either comparable or lower in SNN except for mortality, for which aRR was higher (aRR: 1.28, 95% confidence interval: 1.09-1.50). Propensity score matching and restricting the analysis to infants for which we expect no survival bias, because both networks routinely initiate intensive care at birth, revealed comparable aRR. Variations in observed practices between SNN and US-VON were large.

Conclusions: The SNN units had a significantly lower risk ratio for death or major morbidity. Despite higher mortality, this difference is independent of survival bias. The higher delivery room mortality reflects the SNN practice to favor primary nonintervention for infants born <24 completed gestational weeks. We propose further research into which practice differences have the strongest beneficial impact.