Plasma triacylglycerol (TG) fatty acid composition of healthy non-pregnant and non-lactating women, expectant mothers and their term neonates from Seoul, South Korea was investigated. They were ethnically homogenous and the women had comparable age and parity. Blood samples were obtained at recruitment, third trimester and birth from the non-pregnant women, expectant mothers and neonates respectively. Percent levels of linoleic and arachidonic acids and n-6 metabolites and total n-6 were significantly lower in the pregnant women than in the non-pregnants (p < 0.0001). Similarly, there were lower levels of alpha-linolenic (p = 0.033), eicosapentaenoic and docosahexaenoic acids and n-3 metabolites and total n-3 (p < 0.0001) in the expectant mothers. Compared with their mothers, the neonates had higher proportions of dihomo-gamma-linolenic, arachidonic, docosatetraenoic and docosapentaenoic acids and n-6 metabolites (p < 0.0001) and lower linoleic acid (p < 0.0001). Of the n-3 series, alpha-linolenic acid was lower (p < 0.0001) and eicosapentaenoic, docosapentaenoic and docosahexaenoic acids and n-3 metabolites and total n-3 higher (p < 0.0001) in the neonates compared with their mothers. The study reveals that pregnancy is associated with a reduction in the relative levels of plasma triacylglycerol arachidonic and docosahexaenoic acids. Moreover, it indicates that the decline is a manifestation of selective transfer of these fatty acids to the developing fetus.