Evidence that the essential fatty acid (EFA) status during pregnancy and at birth may not be optimal is mainly based on fatty acid profiles of maternal and neonatal plasma phospholipids. However, erythrocyte phospholipids may be more reliable than plasma phospholipids to reflect the EFA status of an individual. Therefore, the present study compares the levels of EFA and of their derivatives (LCPUFA) in erythrocyte and plasma phospholipids collected during pregnancy and at delivery of 184 women and of their infants at birth. In general, the relative concentrations of erythrocyte and plasma phospholipid fatty acids (% of total fatty acids) were strongly correlated, but not at early pregnancy. The overall changes in fatty acid concentrations during pregnancy were qualitatively comparable between erythrocytes and plasma, although the comparability became less towards the end of pregnancy. The changes in absolute amounts (mg/l) of fatty acids in erythrocyte and plasma phospholipids also compare quite well till 32 weeks of gestation, but not thereafter. Most maternal-neonatal differences in relative fatty acid concentrations are qualitatively comparable for erythrocyte and plasma phospholipids. However, significant differences were observed for the absolute amounts of arachidonic and docosahexaenoic acids. No matter these differences, plasma and erythrocyte phospholipids seem equally suitable to reliably quantify the more functional EFA and LCPUFA status based on fatty acid ratios. Correlations between neonatal and maternal fatty acid values at delivery/birth are highly significant in erythrocyte as well as plasma phospholipids. Neonatal erythrocyte (but not plasma) values also correlated strongly with maternal values at early pregnancy. Therefore, the neonatal EFA and LCPUFA status might be predicted on the basis of EFA and LCPUFA concentrations of maternal erythrocyte phospholipids at early pregnancy.