The effects of vibroacoustic stimulation on baseline heart rate, breathing activity, and body movements of normal term fetuses

To determine the fetal biophysical effects of vibroacoustic stimulation produced by an electronic artificial larynx we studied 20 normal term pregnancies assigned either to control (no stimulus) or experimental (stimulus) groups. Each fetus was observed for 3 hours; either no stimulus or a 3-second stimulus was delivered after the first hour. Fetal heart rate baseline and variation, breathing movement incidence, rate, and variation, and body movement incidence data were acquired concurrently and analyzed at 15-minute intervals. Intergroup comparisons showed that, after stimulation, fetal heart rate baseline and variation increased significantly, whereas breathing incidence fell during the first 15 minutes. Within-group analyses showed that poststimulus elevation of fotal heart rate baseline was the only significant time interaction over the 3 hours. Vibroacoustic stimulation appears to be primarily associated with transient alterations in fetal heart rate baseline; concomitant changes in breathing activity probably reflect normal biologic cycles.