Variations in the number of births by day of the week, and morbidity and mortality in very-low-birth-weight infants

Objective: To know the distribution of births of very low birth weight infants by day of the week, and whether this distribution affects the morbidity and mortality in this group of patients. Methods: This was a retrospective analysis of data collected prospectively in the Spanish SEN1500 network (2002–2011). Outborn infants, patients with major congenital anomalies, and those who died in the delivery room were excluded. Births were grouped into “weekdays” and “weekends.” A multivariate logistic regression analysis was conducted to evaluate the independent effect of the birth moment on outcomes, and Cox regression for survival. Results: Out of a total of 27,205 very low birth weight infants born at and/or admitted to the participating centers, 22,961 (84.4%) met inclusion criteria. A reduction of 24% in the number of births was observed during the “weekends” compared with “weekdays”. In the raw analysis, patients born on weekends exhibited higher morbidity and mortality (mortality rate: 14.2% vs. 16.5%, p