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Acceleration of fetal head induced by vibration of maternal abdominal wall in sheep
A J Peters1, R M Abrams, K J Gerhardt
1Department of Obstetrics and Gynecology, University of Florida, Gainesville, 32610-0294, USA.
Objective:
The human body is often exposed to significant vibration stress in the workplace, at home, and during recreational activities. The current study was designed to evaluate whether low- to midfrequency vibrations present at the extraabdominal wall would be attenuated across this wall and what the levels of exposure would be once these vibrations reached the fetal head.
Study Design:
Four pregnant sheep were instrumented with acceleration transducers to obtain acceleration levels at the extraabdominal and intraabdominal walls and at the fetal head. Sine-wave vibration stimulation was applied over a frequency range of 3 to 150 Hz at a constant acceleration level of 2.5 m/sec2 (root-mean-square).
Results:
Vibration of the extraabdominal wall resulted in a frequency-dependent rise in vibration levels at the intraabdominal wall, from 4% to 140% of the input level. At the fetal head a broad peak in response was noted between 6 and 12 Hz, but the overall levels never exceeded 4% of the input level.
Conclusion:
Fetal exposure to localized vibratory stimulation of the maternal abdomen is maximal in the range of 6 to 12 Hz.