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Fetal vibroacoustic stimulation test
Last reviewed: 08.07.2025
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It is known that vibroacoustic stimulation causes a reaction from the fetus and can be used to assess its condition.
In a normal pregnancy, the test is always associated with the appearance of fetal movements felt by the mother. The fetal response to stimulation is more active the longer the pregnancy term. The test can be used as an initial screening of the fetus's condition, but further studies with neurological and auditory control are needed for the method to be recommended for widespread clinical practice. In this regard, it is important to take into account the sound environment surrounding the fetus in the uterine cavity during labor. It has been shown that in most women, their own cardiovascular noises in the uterine cavity are not heard during labor. The main intrauterine noises are low-frequency sounds with a frequency below 100 Hz and a sound intensity of 60-85 dB. All maternal sounds in the uterine cavity (bowel movements, etc.) are clearly heard, reporting on the main intrauterine background. The intrauterine acoustic environment changes significantly under the conditions of antenatal acoustic stimulation. Vibroacoustic stimulation with an “artificial larynx” device with a sound level of 110 dB, an average frequency of 60 Hz and a stimulation duration of 1-2 s causes tachycardia in 1/3 of fetuses without significant differences at different stages of pregnancy.
Acoustic stimulation of the fetus in the early period of labor is performed to predict the further condition of the fetus. Some authors believe that the vibroacoustic stimulation test can replace the determination of the pH of the blood of the skin of the fetal head in case of threatening changes in the heart rate. It is important to take into account the effect of vibroacoustic stimulation on the organization of behavioral reactions of the fetus. During the last third of pregnancy, the human fetus undergoes a gradual development of behavioral reactions. These reactions reflect the degree of maturity of the brain, they are similar in their manifestations to the reactions of a newborn. In fetuses with growth retardation, as well as in fetuses whose mothers suffer from type I diabetes, there is a delay in the development of behavioral reactions. Normal fetuses respond to vibroacoustic stimulation with motor reactions and prolonged tachycardia. The meaning of behavioral reactions of the fetus is still not entirely clear.