Association between nonacidified standard and high‐protein human milk fortifiers and increased weight velocity relative to acidified human milk fortifiers in preterm infants: A retrospective cohort study

Background Fortification of human milk is necessary for preterm infant growth. We evaluated the impact of an acidified human milk fortifier and nonacidified human milk fortifiers on growth velocity in preterm infants. Methods This retrospective, single‐center study compared preterm infants ( N = 375) receiving either acidified human milk fortifier ( n = 163) or a combination of standard‐protein and high‐protein human milk fortifier ( n = 212) in a tertiary neonatal intensive care unit. Infants with a birth weight of 500–1800 g and feeding initiation by day of life 7 were eligible for inclusion. The coprimary outcome was weight velocity (g/kg/day) at day of life 28 and 36 weeks' postmenstrual age. Multivariable linear regression model for the coprimary outcomes and growth‐related secondary outcomes were adjusted for gestational age, birth weight, sex, and race. Results Infants receiving standard‐protein/high‐protein human milk fortifiers demonstrated higher weight velocity at day of life 28 (12.09 ± 3.27 vs 10.92 ± 3.06 g/kg/day, P < 0.001) and 36 weeks' postmenstrual age (13.31 ± 2.23 vs 12.67 ± 2.28 g/kg/day, P = 0.02) compared with those receiving acidified human milk fortifier. Length velocity at day of life 28 was greater in the standard‐protein/high‐protein group (1.09 ± 0.54 vs 0.97 ± 0.43 cm/week, P = 0.02) but not at 36 weeks' postmenstrual age ( P = 0.06). Human milk exposure and incidence of comorbidities were similar between groups. Conclusions Standard‐ and high‐protein human milk fortifiers were associated with improved weight and length growth in preterm infants.