DOPPLER-ECHOCARDIOGRAPHIC ASSESSMENT OF B LOOD-FLOW OVER THE FETAL AORTIC AND PULMONARY VALVES IN THE 2ND HALF OF PREGNANCY

Pulsed Doppler velocimetry of the fetal aortic and pulmonary valves de rived in the five-chamber-view and short-axis view were performed in 8 8 uncomplicated pregnancies between the 20th and 40th week of gestatio n. The maximal and mean velocities were assessed for both semilunar va lves. Considering the valve diameters and heart rate the stroke volume and cardiac output for both ventricles were calculated. Furthermore, the common stroke volume, common cardiac output and the ratio of right to left cardiac output were calculated. Normal ranges for all these p arameters were constructed and correlated with gestational age. The ma ximal velocities were higher in the aorta than in the pulmonary trunk, but no differences were found in the mean velocities. The stroke volu me and cardiac output of the right ventricle were in higher ratio 1,3: 1 than that of the left ventricle as an expression of the right ventri cular dominance in the fetus. Intracardiac Doppler flow velocimetry gi ves an insight into the physiology of fetal circulation and is a basis for the analysis of blood flow under pathological conditions.