Growth at 2 years in children born preterm: donor milk versus preterm formula

Abstract

Background: The NICHD Neonatal Research Network MILK Trial randomized infants born preterm to receive donor milk or preterm formula. We hypothesized that there would be no growth differences at follow-up by study diet. Methods: We conducted a secondary analysis of the double-blind trial of infants <29 weeks’ gestation or <1000 g at birth at 15 US centers (September 2012–March 2019). Infants were randomized to receive donor milk or preterm formula. The primary outcome was body mass index (BMI) Z-score at 22–26 months corrected age. Results: Among 483 trial participants, 376 were seen at follow-up (181 donor milk, 195 formula). At 22–26 month follow-up, anthropometrics were similar for the two groups, including BMI Z-score (donor milk 0.21 ± 1.13, formula 0.23 ± 1.28, p = 0.67). There was a greater increase in weight Z-score between discharge and follow-up for children randomized to donor milk (donor milk 1.04 ± 1.28, formula 0.73 ± 1.30, p = 0.004). Conclusions: While BMI Z-scores were similar at 22–26 months corrected age, patterns of growth between discharge and follow-up differed by study diet. Children fed donor milk in early infancy showed a greater increase in weight Z-score between discharge and follow-up than children fed preterm formula in early infancy. Impact: At 2 years, the anthropometrics were similar for children randomized to donor milk or preterm formula in early infancy. Patterns of growth between discharge and follow-up differed by early infancy diet. There was a greater weight Z-score increase between discharge and follow-up for children randomized to donor milk than formula. Donor milk appears to be non-inferior to preterm formula with respect to growth at 2 years for children born extremely preterm. Policies and practices that facilitate parental milk provision and donor milk availability are needed for infants born extremely preterm.