Metabolic adaptations during pregnancy are essential to meet the physiological demands of pregnancy as well as adequate growth and development of the fetus. There has been considerable interest in carbohydrate metabolism during pregnancy, with diabetes, the main disorder of glucose metabolism, a considerable focus for research. Whereas disorders of protein and lipid metabolism are recognised during pregnancy, their influence has received less attention. Fasting glucose values fall in early pregnancy with a rise in plasma free fatty acids, enhanced ketogenesis and a fall in plasma amino acids. Decreased hepatic insulin sensitivity in later pregnancy plays a key role in bringing about the appropriate changes in carbohydrate, lipid and amino acid metabolism which are essential for normal fetal development and survival.