In Preterm Infants, Length Growth below Expected Growth during Hospital Stay Predicts Poor Neurodevelopment at 2 Years

BACKGROUND: In preterm infants, neonatal weight growth is associated with neurodevelopmental outcome but is a poor indicator of growth quality. OBJECTIVE: The aim of this work was to measure the relationship between neonatal length growth and the 2-year neurological outcome in preterm infants. METHODS: A total of 2,403 infants enrolled in the LIFT cohort with gestational age less than 34 weeks were studied. Neonatal observed length growth (OLG) was calculated as the change in length Z-score between birth and discharge. Expected length growth (ELG) was estimated based on gestational age, birth weight Z-score, birth length Z-score, gender, and observed neonatal weight growth. The difference between OLG and ELG (∆OLG-ELG) was calculated as OLG - ELG, and infants were ranked into 3 classes depending on their ∆OLG-ELG (≤-0.5, -0.49 to 0.49, ≥0.50 Z-score). We explored the relationship between ∆OLG-ELG and 2-year neurodevelopmental outcome (n = 2,036), and, in a subgroup (n = 85), between ∆OLG-ELG and body composition at discharge. RESULTS: ELG was strongly predicted from the above-mentioned parameters (R2 = 0.73, p = 0.001). OLG correlated closely with gestational age (p = 0.001) but ∆OLG-ELG did not (p = 1.0). OLG was not associated with a 2-year nonoptimal outcome after adjustment for gestational age, but ∆OLG-ELG ≤-0.5 was; the crude and adjusted odds ratios were 1.63 and 1.56, respectively. ∆OLG-ELG correlated negatively with fat mass (R2 = 0.29, p = 0.006) before and after adjustment for gestational age. CONCLUSION: ∆OLG-ELG is a marker of neonatal growth that does not depend on gestational age, and may reflect quality of growth. A ∆OLG-ELG ≤-0.5 Z-score is associated with a higher risk for 2-year nonoptimal neurodevelopmental outcome.