Computerised cardiotocography following vibro-acoustic stimulation

To study the effect of vibro-acoustic stimulation (VAS)to the mean fetal heart rate (FHR), period of high and low FHR variation, overall variation (msec and bpm)and short term variation (msec). In a prospective study 17 pregnant women between 34±42 weeks gestation admitted to antenatal ward for obstetric complicationtwo 60 min FHR recording was carried out with an interval of 30 min in between recordings. On a random basis the fetus was stimulated by a vibro-acoustic stimulator for 5 sec at the beginning of one of the two 60 min FHR recordings. Automated analysis of the FHR, tocodynamometry, and maternal perception of fetal movements was done by a commercially available computerized programme (System 8000).It was possible to obtain the two 60 min recordings with signal loss of < 10% in 12 out of 17 patients.No changes were observed when the FHR parameters for 60 min after VAS was compared with the controlperiod. When analyzed in segments of 0 to 10, 11 to 20, 20 to 40 and 41 to 60 min the mean baseline FHR was significantly higher after VAS during the first 10 minutes compared with any 10 or 20 min segment of the control period or any such segments 10 min after VAS. Concomitantly the overall variation and shortterm variation was significantly lower during the first 10 minutes following VAS (p < 0.05) compared with the parameters in the corresponding periods during the control period. The mean period of high and low FHR variability episodes, mean overall variation and short term FHR variation was similar in the recordings obtained with and without VAS from 11 to 60 min.The FHR changes following VAS affected the mean baseline FHR and the overall and short-term variation only for the 10 min and did not cause FHR disturbance beyond this period.