ABSTRACT
Two-dimensional-directed M-mode echocardiography was done on 80 normal fetuses between
the 17th to 42nd weeks of gestation. The M-mode beam transected the ventricles at
the level of the chordae tendineae at the tip of atrioventricular valves. Right and
left ventricular dimensions and free wall thicknesses correlated well with gestational
age. Calculated measurements showed a good correlation of the stroke volume and cardiac
output with gestational age. The right ventricular dimension, however, was significantly
greater than the left ventricular one. Fractional shortening of the right and left
ventricle did not change significantly with advancing gestational age. This study
indicates that the human fetal right ventricle dimension, stroke volume, and cardiac
output are slightly larger than that of the left ventricle. This study also suggests
that the human fetus increases its cardiac output to match its growth and it does
so by increasing ventricular size rather than fractional shortening or heart rate.
