Abstract: Breastfeeding is important for brain development and was shown by many studies to result in higher scores Intelligent Quotient (IQ). However, the exact mechanism whereby Breastfeeding influences cognitive development remains unclear. This work aimed to study the expression of genetic code FADS2 linked to the cognitive function in relation to the mode of feeding. The study comprised 30 preterm infants of 32 to 34 weeks gestation age including 15 exclusively breastfed and 15 fed on Infant Milk Formula (IMF) selected from the Neonatal Intensive Care Unit (NICU) in Talkha Central Hospital in Dakahlia Governorate Egypt. Blood samples were drawn at birth and at 12 weeks of life and FADS2 mRNA gene expression-was measured using real time PCR at birth and at 12 weeks of life. Blood indices were measured at 12 weeks. FADS2 mRNA gene expression demonstrated a significant increase from birth to 3 months, with 109 folds rise in breast fed group compared to five folds rise in the artificially fed group at (p