Background <p>Very preterm infants born before 32 weeks of gestation remain vulnerable to postnatal growth impairment. However, longitudinal data focusing on appropriate-for-gestational-age (AGA) infants are limited. Standard growth references may inadequately reflect the developmental trajectories of this population.</p> Methods <p>We constructed sex-specific growth curves for height, weight, body mass index, and head circumference from term-equivalent age to 6 years postmenstrual age in AGA infants born at &lt;32 weeks of gestation without neurodevelopmental impairments. These trajectories were compared with Japanese national growth standards.</p> Results <p>Infants born before 28 weeks of gestation demonstrated significantly reduced growth relative to national standards, with the greatest deviation occurring between 40 and 60 weeks postmenstrual age. While gradual catch-up growth was observed thereafter, full alignment with standard curves was not achieved. Lower gestational age correlated with more pronounced deficits across all anthropometric parameters. Head circumference remained notably reduced among infants born before 25 weeks, raising concern for potential neurodevelopmental implications.</p> Conclusions <p>Extremely preterm AGA infants experience persistent growth deficits through early childhood. These findings underscore the importance of long-term growth surveillance and early intervention strategies to support optimal physical and neurological outcomes in this high-risk population.</p> Impact <p><UnorderedList Mark="Bullet"> <ItemContent> <p>Many extremely preterm infants grow more slowly than expected well into early childhood.</p> </ItemContent> <ItemContent> <p>Babies born earlier in pregnancy show more delayed physical growth across all measures.</p> </ItemContent> <ItemContent> <p>Infants born before 25 weeks may have a smaller head size, raising concerns for brain development.</p> </ItemContent> </UnorderedList></p>