ESPE Abstracts

Purpose: This study aimed to compare growth patterns and the achievement of catch-up growth (CUG) in small-for-gestational-age (SGA) infants at four years of age, based on the type of feeding during the first 4-6 months, using nationwide data.

Methods: We included full-term 42,295 SGA children (21,917 boys; 52%) who participated in the first (4-6 months), second (9-12 months), third (18-24 months), and fifth (42-48 months) rounds of the National Health Screening Program for Infants and Children (NHSPIC), under the National Health Insurance Service from 2007 to 2014. SGA was defined as birth weights below the 10th percentile for gestational age. The study population was divided into two groups based on the primary milk feeding type: "Breastfed" and "Formula-fed." CUG was defined as a height Standard Deviation Score (SDS) at the 3rd percentile or above by the fifth NHSPIC visit. Propensity scores were used to match the breastfed and formula-fed groups 1:1 based on sex, birth weight, delivery mode, socioeconomic status, and residence. Multivariate logistic regression analysis was performed to evaluate the effect of milk feeding type on CUG at four years of age.

Results: Among the study participants, 49.1% (n = 20,774) were breastfed, and 50.9% (n = 21,521) were formula-fed at 4-6 months. After propensity score matching, both groups included 19,308 infants. Up to the second NHSPIC round, the breastfed group exhibited significantly smaller increases in weight and height Z-scores compared to the formula-fed group. However, from the second round onward, the breastfed group demonstrated faster gains in both metrics (all P < 0.0001). By the fifth NHSPIC, however, the breastfed group showed a lower likelihood of achieving CUG compared to the formula-fed group (Odds Ratio [OR] 0.794, 95% CI 0.665-0.948, P = 0.011). Receiver operating characteristics (ROC) curve analysis indicated that an increase in weight of approximately 1.352 SDS from birth to the first NHSPIC was predictive of CUG at the fifth NHSPIC (Area Under the Curve [AUC] = 0.7685, sensitivity 65.3%, specificity 76.1%).

Conclusion: In a cohort of Korean SGA infants, those breastfed for the first 4-6 months had lower CUG rates at four years than formula-fed infants. Additionaly, adequate weight gain from birth to 4-6 months was found to be crucial for CUG. If weight gain is insufficient in breastfed SGA infants, early nutritional supplementation may be needed. Further research is required to identify factors influencing growth in this key developmental stage.