Early enteral nutrition practices and their association with growth and necrotising enterocolitis in extremely preterm infants—A dual national cohort study

BACKGROUND: In Sweden, the incidence of necrotising enterocolitis (NEC) in extremely preterm infants has increased from 6 to 10% over a decade. We examined whether changes in enteral nutrition during the first 2 weeks were associated with growth and development of NEC. METHODS: The EXPRESS (2004-2007) and EXPRESS 2 (2014-2016) cohorts included infants <27 gestational weeks. NEC diagnoses were validated. Nutritional data were retrieved from four of the six healthcare regions (n = 815). Growth and NEC incidence were compared between cohorts, and odds ratios (OR) were adjusted for early risk factors in a logistic regression model. RESULTS: In EXPRESS 2, during the first postnatal week, feeding advancement was more rapid (10 vs. 8 ml/kg/d, p < 0.001) and fortification more common (27% vs. 3.6%, p < 0.001). Growth improved from birth to 28 days (delta z-scores: weight, -2.18 vs. -1.49, p < 0.001; length, -2.22 vs. -1.96, p = 0.013) and to 36 weeks' postmenstrual age. Neither feeding advancement nor fortification was associated with increased NEC risk >7 d (n = 44; aOR 0.96, 95% CI 0.91-1.01, p = 0.15; aOR 1.33, 95% CI 0.57-2.79, p = 0.50). CONCLUSION: A more active early enteral nutrition policy in Sweden was associated with faster feeding advancement, earlier fortification, increased protein intake, and improved growth without increased NEC risk. IMPACT: Human breastmilk fortification increased, and macronutrient intakes improved among extremely preterm infants in Sweden during the years 2014-2016, compared to 2004-2007. Weight and length growth improved during the years 2014-2016. More active enteral nutrition during 2014-2016 was not associated with an increased incidence of necrotising enterocolitis. The study uses validated, population-based data from two national cohorts with high-resolution daily nutrition and growth records. Findings support earlier feeding advancement and fortification to improve growth without increasing necrotising enterocolitis risk in extremely preterm infants.