Background: Preterm infants requiring prolonged hospitalization in the neonatal intensive care unit (NICU) are often exposed to early-life stress, which may contribute to long-term health consequences. Epigenetic markers, particularly DNA methylation (DNAm) of stress-related genes such as SLC6A4 and NR3C1 , have been identified as potential biomarkers of early-life stress. Limited research has compared DNAm patterns between term and preterm infants or examined associations between NICU-related s