We have studied changes of the electrical heart field resulting from the changed spatial position of the heart during the last period of pregnancy in healthy women. This was suggested to be a good model of electrocardiographic changes that could be found on patients suffering from obesity. The measured parameters of the electrical heart field were compared with hemodynamic parameters before and after delivery in the group of non-obese women with physiological pregnancy and in a group of healthy non-obese and non-pregnant women. Several significant changes of the electrical heart field were detected in the late pregnancy: increased heart rate, shortening of A-V conductance, prolongation of QT interval normalised for the heart rate and changes in the ventricular depolarisation and repolarisation patterns. Some of these changes are not fully restored in 4 days after delivery. Moreover, we have found an increased pump function of the left ventricle accompanied by decreased peripheral resistance in the group of pregnant women. Increased pump function was partially restored after delivery, peripheral resistance was not only restored, but it overshot to increased values. Persisting elevated heart rate with increased peripheral resistance suggested increased sympathetic activity after birth. Only some changes of electrical heart field could be explained by changed spatial arrangement of the chest organs during pregnancy and they must be considered in a complex consequence with changes in regulatory mechanisms.