The Fontan circulation is characterised by passive pulmonary blood flow, with cardiac output dependent on preload, low PVR, ventricular function, and SVR. Pregnancy may destabilise this circulation, increasing the risk of hypoxia, arrhythmia, thromboembolism, cardiac decompensation, and foetal growth restriction. Caesarean section under general or regional anaesthesia adds further haemodynamic challenge.