Static and longitudinal extrauterine growth restriction in very low birth weight infants: prevalence and associated factors.

OBJECTIVES: Extrauterine growth restriction (EUGR) occurs when preterm infants fail to achieve expected intrauterine growth rates. EUGR is classified as static (body weight < 10th percentile at 36 weeks postmenstrual age (PMA) or longitudinal (weight z-score decline > 1 standard deviation from birth to 36 weeks PMA). This study aimed to determine the prevalence of each type and identify associated factors. METHODS: This retrospective cohort study included very low birth weight (VLBW) infants admitted to a tertiary-level NICU between January 2020 and December 2023. Infants who died, were transferred before 36 weeks PMA, or had chromosomal or major anomalies were excluded. RESULTS: Of 107 infants, 55 (51.4%) had static EUGR and 35 (32.7%) had longitudinal EUGR. Multivariable analysis identified SGA as the only significant factor associated with static EUGR (aOR 9.01, 95% CI 2.08-39.08, p = 0.003). Delayed achievement of 120 mL/kg/day after day of life 10 showed a positive association with static EUGR but did not reach significance (aOR 2.57, 95% CI 0.93-7.13, p = 0.069). In contrast, delayed full enteral feeding was the only significant factor associated with longitudinal EUGR (aOR 3.98, 95% CI 1.48-10.68, p = 0.006). Agreement between definitions was weak (κ = 0.186, p = 0.019). CONCLUSION: Static EUGR was strongly associated with SGA status at birth, whereas longitudinal EUGR identified a partially distinct subgroup of infants. Delayed achievement of full enteral feeding was significantly associated with longitudinal EUGR. This finding warrants cautious interpretation, as delayed enteral feeding may serve as a marker of illness severity rather than a direct causal factor.