The authors report the results of a transverse prospective study of 80 normal women, divided into 4 groups of 20: control group, 1st trimester of pregnancy, 2nd trimester of pregnancy, 3rd trimester of pregnancy. These groups were comparable in terms of age, height and haemoglobin level. No significant difference was observed in terms of obstetric profile between the various groups of women. The results did not reveal any difference concerning the morphology of cardiac structures, the parameters of left ventricular diastolic filling and the frequency of valvular regurgitation. On the other hand, diameters and cavity volumes, left ventricular mass, left ventricular ejection fraction, and maximal antegrade aortic and pulmonary blood flow rates were higher during pregnancy; these increases were less marked when the measurements were performed in the dorsal supine position compared to those observed in the left lateral supine position.