The pathophysiology of pre-eclampsia, disease of the endothelium, placental ischaemia, and its consequences on blood pressure and heart rate variations are described. The methods of evaluation of heart rate and blood pressure during pregnancy, outpatient visit clinical measurement, self-measurement, ambulatory measurement, "Finapres", electrocardiogram and Holter ECG are reviewed; the practical implications of the nocturnal fall of vagal tone with tachycardia, demonstrated during pre-eclampsia, are discussed.