Longitudinal analysis of catch-up growth pattern in low birth weight infants up to 5 years in a nationwide Korean cohort.

PURPOSE: This study aimed to investigate catch-up growth (CUG) patterns in low-birth-weight infants (LBW) and identify factors associated with growth trajectories from birth to 5 years, focusing on the relationship between early growth status groups (no early CUG for height only, weight only, or both height and weight, and the normal reference group) and subsequent growth outcomes. METHODS: We conducted a longitudinal analysis of 15,235 infants with low birth weight using nationwide data from the South Korean National Health Insurance Service (NHIS). No early CUG was defined at 4-6 months as height or weight below the 10th percentile based on the 2017 Korean growth charts. Growth outcomes at 1, 2, 3, and 5 years were assessed using logistic and linear regression models. Analyses were adjusted for demographic and clinical factors, including socioeconomic status (SES) and feeding type. RESULTS: Approximately 82% of infants achieved CUG in height by 6 months of corrected age. No early CUG in height and weight group had the lowest average birth weight, and inadequate CUG in height was most prevalent at one year of age, persisting across all periods and consistently showing the highest prevalence at five years of age. Height and weight z-scores at the first screening visit (4-6 months of corrected age) highlighted the greater influence of initial height on later height. CONCLUSION: This study highlights the importance of early-life conditions and interventions in shaping the growth trajectories of LBW infants, emphasizing the significance of height catch-up.