Arachidonic acid is preferentially biomagnified over DHA in fetal erythrocytes: evidence from 172 paired maternal–cord samples in Oman

The selective transfer of long-chain polyunsaturated fatty acids (LCPUFAs) from mother to fetus is essential for fetal development, particularly neurodevelopment and membrane synthesis. While docosahexaenoic acid (DHA) has been the focus of research, emerging evidence suggests arachidonic acid (AA) may be more strongly biomagnified across the placenta. We hypothesized that arachidonic acid (AA) would be preferentially biomagnified over docosahexaenoic acid (DHA) in fetal erythrocytes compared to maternal erythrocytes. This cross-sectional study investigated fatty acid biomagnification using erythrocyte membrane composition as a long-term indicator of status. Paired maternal venous and umbilical cord blood samples were collected at delivery from 172 healthy Omani mother-infant pairs. Fatty acids were analyzed via gas chromatography and expressed as relative proportions (%) and absolute concentrations (mg/mL). Wilcoxon signed-rank tests and Spearman correlations assessed differences and associations. AA showed significant biomagnification, increasing from 13.55 % in maternal to 14.87 % in fetal erythrocytes (p < 0.001), while DHA increased modestly (4.11 to 4.40%, p = 0.034). Linoleic acid (LA), a precursor to AA, was significantly lower in fetal blood, indicating selective exclusion. Ratios such as AA/LA, AA/DHA, and (AA+DHA)/MUFAS were elevated in fetal erythrocytes, suggesting strong placental lipid selectivity. In contrast, monounsaturated fatty acids (MUFAS) and precursors such as α-linolenic acid (ALA) and EPA were reduced. Significant maternal-fetal correlations were found for AA, DHA, and composite indices. These findings demonstrate preferential biomagnification of AA, underscoring its physiological importance during gestation. Erythrocyte membrane profiling provides a stable measure of fatty acid transfer and highlights the need to revisit maternal dietary guidelines and infant formula composition.