Supplementary Material for: Risk Factors for Necrotizing Enterocolitis: A Prospective Multicenter Case-Control Study

<b><i>Background:</i></b> The identification of independent clinical risk factors for necrotizing enterocolitis (NEC) may contribute to early selection of infants at risk, allowing for the development of targeted strategies aimed at the prevention of NEC. <b><i>Objective:</i></b> The objective of this study was to identify independent risk factors contributing to the development of NEC in a large multicenter cohort. <b><i>Methods:</i></b> This prospective cohort study was performed in 9 neonatal intensive care units. Infants born at a gestational age ≤30 weeks were included. Demographic and clinical data were collected daily until day 28 postnatally. Factors predictive of the development of NEC were identified using univariate and multivariable analyses in a 1: 5 matched case-control cohort. <b><i>Results:</i></b> In total, 843 infants (56 NEC cases) were included in this study. In the case-control cohort, univariate analysis identified sepsis prior to the onset of NEC and formula feeding to be associated with an increased risk of developing NEC, whereas the administration of antibiotics directly postpartum was inversely associated with NEC. In a multivariable logistic regression model, enteral feeding type and the number of days parenterally fed remained statistically significantly associated with NEC, whereas the administration of antibiotics directly after birth was associated with a lower risk of developing NEC. <b><i>Conclusions:</i></b> Formula feeding and prolonged (duration of) parenteral feeding were associated with an increased risk of NEC. Contrary to expectations, the initiation of treatment with antibiotics within 24 h after birth was inversely associated with NEC.