[Doppler echocardiographic analysis of blood flow through the fetal aorta and pulmonary valve in the second half of pregnancy].

Pulsed Doppler velocimetry of the fetal aortic and pulmonary valves derived in the five-chamber-view and short-axis view were performed in 88 uncomplicated pregnancies between the 20th and 40th week of gestation. The maximal and mean velocities were assessed for both semilunar valves. 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 parameters were constructed and correlated with gestational age. The maximal velocities were higher in the aorta than in the pulmonary trunk, but no differences were found in the mean velocities. The stroke volume 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 ventricular dominance in the fetus. Intracardiac Doppler flow velocimetry gives an insight into the physiology of fetal circulation and is a basis for the analysis of blood flow under pathological conditions.