Trimester-Specific Associations Between Maternal Fatty Acid Ratios and Cognitive and Executive Functioning in 4-Year-Old Children

Purpose: Early prenatal fatty acid balance is vital for brain development, yet trimester-specific effects on long-term neurodevelopment remain unclear. This study examined associations between maternal omega-6/omega-3 (n-6/n-3) ratios in the first and third trimesters and child neurodevelopment at age four. Methods: In the ECLIPSES cohort (n = 223), maternal serum n-3 and n-6 fatty acids were measured at 12 and 36 gestational weeks. At age four, children’s cognitive and executive function were assessed using the Wechsler Preschool and Primary Scale of Intelligence (WPPSI), and the Behavior Rating Inventory of Executive Function (BRIEF)—Preschool Version, respectively. Multivariable regression models were adjusted for sociodemographic and lifestyle factors. Results: A higher n-6/n-3 ratio in the first trimester was significantly associated with poorer executive functioning, as reflected by higher BRIEF scores indicating greater difficulties in inhibition (b = 2.45, p = 0.002), working memory (b = 1.87, p = 0.030), planning/organization (b = 2.20, p = 0.004), and the Global Executive Composite (b = 1.96, p = 0.006). Higher first-trimester ratios were also associated with lower WPPSI working memory performance (b = −2.14, p = 0.013), while general cognitive abilities were largely unaffected. Conclusions: An elevated maternal n-6/n-3 ratio in early pregnancy is associated with poorer executive function in preschool children, whereas evidence linking these ratios to general cognition remains limited. These findings indicate that associations between fatty acid balance and executive function were mainly observed during the first trimester.