[Fetal photoplethysmography as a diagnostic parameter for fetal distress in pregnant rabbits (author's transl)].

The changes in fetal photoplethysmogram and fetal heart rate were determined in pregnant rabbits, under the stress by pressing the abdominal aorta and thereby decreasing the blood flow there. ECG, heart rate, direct blood pressure and blood flow of the abdominal aorta in pregnant rabbits were also measured simultaneously. When the blood flow was reduced by 20 percent, the wave height of fetal photoplethysmogram was decreased by 40 percent but the fetal heart rate remained unchanged. When the blood flow was reduced by 50 percent, the wave height was correspondingly decreased by 50 percent and the fetal heart rate fell off from 180 b.p.m. to 60 b.p.m. The fetal heart rate returned to 120 b.p.m. 60 seconds after resumption of blood flow. When the blood flow was reduced to less than 20 percent, the wave height was decreased by 60 percent and the fetal heart rate fell off 20 seconds later. These results indicate that the fetal photoplethysmogram, mainly the wave height, has already undergone a change even before the fetal heart rate turns into reversible bradycardia. The fetal photoplethysmography may, therefore, be useful to grasp the early changes in fetal hemodynamics.