SUN-206 - Early Postnatal Growth Predictors of Catch-Up Growth in Term Small-for-Gestational-Age Infants: A Nationwide Propensity-Score-Matched Study

Background: Infants born small for gestational age (SGA) are at risk for impaired growth and metabolic complications. However, the long-term effects of early feeding type on catch-up growth (CUG) in SGA infants remain controversial, and there have been no established anthropometric thresholds to predict later CUG.

Methods: This population-based study analyzed full-term SGA infants enrolled in the National Health Screening Program for Infants and Children (NHSPIC) in South Korea. Anthropometric data were collected at 4–6, 9–12, 18–24, 30–36, and 42–48 months. Feeding type was classified as exclusively breastfed or exclusively formula-fed based on parent-reported data from the 1st (4–6 months) and 2nd (9–12 months) NHSPIC rounds. SGA was defined as a birth weight below the 3rd percentile, and CUG as achieving a height above the 3rd percentile by 42–48 months. Propensity-score matching (1:1) was applied for sex, birth weight, socioeconomic status, and residence. Logistic regression and receiver operating characteristic analyses were used to identify predictors of CUG.

Results: Among the 2,913 infants included, 31.4% were breastfed and 68.6% were formula-fed. Formula-fed infants exhibited faster early growth, but intergroup differences diminished after 9-12 months, resulting in comparable CUG rates at four years of age. Feeding type was not significantly associated with CUG (adjusted odds ratio 1.38; 95% CI 0.76–2.51). In contrast, weight and height Z-scores at 4–6 months independently predicted later CUG (AUC 0.77 and 0.84, respectively).

Conclusion: Early postnatal growth adequacy, rather than feeding type, was the key determinant of later catch-up growth in term SGA infants. Despite slower initial growth, breastfeeding supported equivalent long-term outcomes and may represent a physiologically favorable trajectory. Early assessment of growth parameters at 4–6 months can guide timely intervention for infants at risk of persistent growth failure.

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