Fetal responses to different intensity levels of vibroacoustic stimulation.

The fetal responses to three different intensity levels of vibroacoustic stimulation (mean 92, 103, and 109 dB) were investigated in 275 pregnant women between 32-42 weeks of gestation. A 103-dB and a 109-dB stimulation aroused fetal movements, perceived by the mother, significantly more often than did a 92-dB stimulation (P less than .05 and P less than .01, respectively). Fetal heart rate (FHR) accelerations occurred slightly more often at a 109-dB stimulation than at a 92-dB level, but the difference was not significant. In the second part of the study, the three modes of stimulation were compared under standardized conditions in ten normal patients. The immediate reaction concerning fetal body movements as measured by the mother or the observer and FHR accelerations were the same as described earlier. There was a significant delayed increase of fetal gross body movements after 8 minutes at the 103- and 109-dB stimulation levels. Thus, the fetal response to vibroacoustic stimulation changes with different intensity levels.