Maternal haemodynamic changes during spinal anaesthesia for caesarean section have traditionally been evaluated by noninvasive blood pressure and heart rate. Recent publications have addressed the importance of cardiac output measurement in the assessment of the maternal circulation. In this review, a physiological approach is suggested for the prevention and treatment of haemodynamic instability during caesarean section in healthy women and in those with preeclampsia or cardiac disease. A better understanding of the maternal haemodynamic effects of spinal anaesthesia and the effects of vasopressors has emerged from the monitoring of cardiac output during caesarean section in healthy women and in those with severe preeclampsia or cardiac disease. Based on maternal physiological arguments, phenylephrine is the vasopressor of choice in healthy pregnant women. New work demonstrating cardiac dysfunction in some women with severe preeclampsia has implications for risk assessment and anaesthesia. Recent publications suggest that combined spinal-epidural and continuous spinal anaesthesia is well tolerated in pregnant women with cardiac disease. The most frequent response to spinal anaesthesia for elective caesarean section is a marked decrease in systemic vascular resistance and partial compensation from increased stroke volume and heart rate. Early administration of phenylephrine by bolus or continuous infusion is indicated in most cases. Recent work has expanded our knowledge of the therapeutic range of phenylephrine and indicates that the heart rate response to vasopressors is a good surrogate marker for cardiac output. Further research should examine haemodynamic changes during spinal anaesthesia in high-risk pregnant women with early onset preeclampsia or cardiac disease.