Extrauterine Growth Restriction and Catch-up Growth Following NICU Discharge: A Tale of two Standards

Aim: Extrauterine growth restriction (EUGR) is common in premature infants, but the progression after neonatal intensive care unit (NICU) discharge is not well described. We aimed to assess EUGR after NICU discharge and to identify factors associated with catch-up growth (CUG) and neurodevelopmental outcomes at 2 years of age. Methods: Growth parameters at birth, 36 weeks postmenstrual age (PMA), and two neurodevelopmental follow-up visits for preterm graduates of our NICU were reviewed. EUGR was assessed using Fenton and Intergrowth-21 standards. Factors associated with outpatient growth and neurodevelopmental outcomes at 2 years of age were evaluated using logistic and linear regression. Results: 369 infants born at 24–32 weeks gestation comprised the cohort. EUGR prevalence was 14.9% for Intergrowth-21 versus 56.4% for Fenton (p <.001). Although there was a significant decrease in weight z-score from birth to 36 weeks PMA, weight z-scores returned to their birth weight values at the second clinic visit (86 weeks PMA). Infants who received formula as opposed to human milk (HM) showed faster CUG. Higher scores in the Bayley-III scale at 2 years of age were associated with HM feeding. Discussion/Conclusion: Fewer infants were identified as EUGR when Intergrowth-21 versus Fenton growth standards were used, which categorizes infants with adverse clinical courses and poorer neurodevelopmental outcomes more distinctly. While growth failure during the birth hospitalization is common in preterm infants, outpatient CUG was demonstrated, with return to birth weight z-score. Our findings suggest that HM feeding may have a positive impact on cognitive, language, and motor developmental outcomes for preterm infants despite less rapid CUG.