The effect of vibratory acoustic stimulation on fetal middle cerebral artery impedance and instantaneous fetal heart rate: 1. a transversal study on fetuses with 35 to 41 weeks of gestational age - Revista Brasileira de Ginecologia e Obstetrícia

SUMMARY Purpose: to examine the response of the fetal heart rate (FHR) and middle cerebral artery resistance (MCA PI) to vibratory stimulation (VAS) in normal human fetuses. Methods: when the fetuses were without activity (in apnea and without corporal movements), we obtained baseline measurements of MCA PI and FHR before and after the application of a 3-sec vibratory acoustic stimulus. Real time ultrasonography with pulsed wave and color Doppler imaging was used for the execution of the study. The VAS was performed using a bicycle horn with 400 to 4000 Hz and sound pressure was 65 to 110 dB. Results: the FHR before VAS was 139 ± 3.14 bpm and after VAS was 153 ± 7.23 bpm (p<0.0001). The MCA PI rate before VAS was 1.84 ± 0.07 and after VAS was 1.56 ± 0.04 (p<0.001). In all cases we observed a fetal response with vigorous corporal movements, FHR rise and MCA PI reduction after VAS. Conclusions: we conclude that VAS, in human fetuses near term, for 3 sec as described in this study, determines some response, with increase in FHR and corporal movement and MCA PI reduction. Although we have a tendence to say that VAS determines fetal cerebral flow increase, these data do not allow such clinic interpretation.