The advent of fetal echocardiography combined with Doppler technology gave the clinicians the possibility to evaluate and clarify the main aspects of fetal and postnatal circulatory physiology. From the end of cardiogenesis to the end of gestation the developmental changes of the fetal myocardial structure, ventricular function and circulatory physiology have all been studied. Also the physiological features of the transitional circulation in the first postnatal period, as well as the developmental changes in the morphology and function of the neonatal ventricles can be assessed by Doppler echocardiography. This review is divided in two parts. In the first one we will briefly discuss the contractile properties of the fetal myocardium, the cardiac performance and dynamics of the fetal circulation; in the second one we will consider the physiological aspects of the transitional circulation, the structural features of the immature neonatal myocardium, as well as the developmental changes of the myocardial mechanics as shown by Doppler ultrasound.