Adaptations of maternal lipid metabolism during pregnancy are directed toward both the needs of the fetus for lipid substrates and maternal requirements for lipid stores serving as energy reserves for lactation. The mechanisms are poorly understood, but must be elucidated before new dietary recommendations can be made about dietary supplementation with long-chain polyunsaturated fatty acids (LC-PUFA). Problems of high priority for research are: (1) Fetal requirements for specific fatty acids, including essential fatty acids (EFA) and long-chain polyunsaturated fatty acids (LC-PUFA); (2) The mechanisms for transfer of fatty acids across the placenta; (3) The role of very low density lipoproteins (VLDL) in transfer of EFA and LC-PUFA from the maternal liver to the placenta; (4) Adjustments of fatty acid metabolism in the maternal liver during pregnancy; and (5) The effect of dietary LC-PUFA on maternal fatty acid metabolism during pregnancy.