A study of correlation of individual biophysical variables and vibroacoustic stimulation with perinatal outcome

Vibroacoustic stimulator provokes a physiological sympathetic range response characterized by fetal heart rate acceleration suggesting an intact non-hypoxic CNS. To improve the sensitivity other variables of fetal well being should be added to acoustic stimulation. Visual Acoustic Stimulation Test (VAST) utilizes ultrasound to evaluate the fetal responses to acoustic stimulation. Observation of fetal startle response to vibroacoustic stimulus was found to be associated with a FBP score of eight and above. Vibroacoustic stimulation has been reported to wake up the fetus from sleep cycles and hence reduce false positive results. Most fetuses after 30-32 weeks respond to acoustic stimulation. The observation time after VAST is maximum ten minutes, Fetal V.A.S.T. predicted perinatal outcome with highest accuracy, is highly sensitive, specific with low false positive and negative rates Mean testing time in our study was 5.32 ± 0.68 minutes. The subjects with normal startle were 154 and out of which 67(43.50%) had normal perinatal growth while 87(56.50%) had abnormal perinatal growth. With total 46 subjects with abnormal startle 8(17.39%) had normal perinatal growth while 38(82.16) had abnormal perinatal growth. The association was found to be statistically significant (p<0.005). In total 97 of normal fetal growth, 70(72.16%) had normal perinatal outcome and with 103 total abnormal growth only 5(4.85%) had normal perinatal outcome and rest 98(95.15%) had abnormal perinatal outcome. VAST results were 87.2% sensitive, 80% specific with a positive predictive value of 87.9% and an accuracy of 84.5%.