Interdependence of pulse wave variables in the human fetal aorta.

The problem of inferring the state of fetal circulation from diameter pulse waves in the descending aorta was studied with the aid of statistical methods in 12 fetuses in late uncomplicated gestation. By means of a phase-locked, echo-tracking ultrasound technique, aorta diameter-time waveforms and pulse propagation velocities were measured. In a factor analysis, three independent factors explained 75% of the total variance of variables in the waveforms. Relationships between some of the variables and biophysical events are suggested; they await confirmation from animal experiments, in order to develop a practical method for assessing fetal circulation.