Obstetrics describes the care related to pregnancy. An understanding of the changes in maternal physiology and pathophysiology of pregnancy-related disorders is essential to provide safe, effective obstetric care. This chapter summarises the implications the physiological changes occurring in pregnancy will have on anaesthetic practice. The physiological changes include changes in cardiovascular and haematological system, respiratory system, gastrointestinal system and central nervous system. Patients with cardiovascular disease need close monitoring and multidisciplinary care throughout the pregnancy with the involvement of obstetricians, anaesthetists, intensivists and cardiologists. Pregnant patients should be considered to be at risk from aspiration from approximately 16/40 (before if symptoms of reflux). Patients should be premedicated with an H2-blocking drug the evening before and on the morning of Caesarean section. 30ml 0.3 Mol sodium citrate should be given immediately before a rapid sequence induction with cricoid pressure, which is used when administering general anaesthesia.