Abstract
A healthy foetus, if exposed to external sound stimulation, often responds with vigorous movements which can be felt by the mother. A hypoxic foetus usually does not show this response. To evaluate the fetal acoustic stimulation test (FAST) in antepartum fetal monitoring. Prospective interventional study carried out at the Teaching Hospital, Galle. An initial non-stress test (NST) followed by a FAST using the Corometric model 146 was carried out in 423 high risk pregnant women. The response to FAST was assessed and compared with the NST. A repeat NST was recorded in women who had an initial non-reactive NST. The results of the NST and FAST were compared with the fetal outcome if the woman delivered within 24 hours. Maternal perception of fetal movements after FAST, results of NST before and after FAST, and the babies' 5 minute Apgar scores if delivered within 24 hours of the FAST. Of the women, 349 (82.5%) noticed fetal movements after FAST. Of the 167 women who complained of absent or reduced fetal movements, 67% felt fetal movements after FAST. Ninety one had a nonreactive NST and 43 (47%) became reactive after FAST. Compared to the NST, the FAST had less sensitivity (93% vs 100%, p = 0.01), better specificity (79% vs 45%, p = 0.001), better positive predictive value (67% vs 50%, p = 0.02), similar negative predictive values (96% vs 100%, p > 0.05) and better accuracy (83% vs 69%, p = 0.03) in predicting neonatal asphyxia (5 minute Apgar score < 7) if the baby was delivered within 24 hours after the test. The FAST is a reliable, cost effective screening test for antepartum fetal monitoring. It significantly reduces the false positive (non-reactive) NST and has a good negative predictive value.
Highlights
The fact that a foetus is sensitive to external environmental sound vibration and that it responds to it was observed almost 80 years ago [1]
Compared to the non-stress tests (NST), the fetal acoustic stimulation test (FAST) had less sensitivity ( 93 % vs 100 %, p = 0.01 ), better specificity ( 79 % vs 45 %, p = 0.001 ), better positive predictive value ( 67 % vs 50 %, p = 0.02 ), similar negative predictive values ( 96 % vs 100 %, p > 0.05 ) and better accuracy ( 83% vs 69%, p = 0.03) in predicting neonatal asphyxia ( 5 minute Apgar score < 7) if the baby was delivered within 24 hours after the test
Subsequent reports of the fetal heart rate increasing with sound stimulation led to its use for antepartum fetal monitoring, especially in the USA, where the use of a fetal acoustic stimulation test (FAST) was described [2,3]
Summary
The fact that a foetus is sensitive to external environmental sound vibration and that it responds to it was observed almost 80 years ago [1]. Ultrasound studies have shown that the fetal response to sound stimulation is analogous to the newborn startle reflex and that it is a consistent phenomenon from the 28th week of pregnancy [4]. As these movements are strong and vigorous they are more readily recognised by the mother than spontaneous fetal movements [5]. Maternal perception of fetal movements in response to FAST has a higher sensitivity [8] In both high and low risk pregnancies, it has been found to be a useful screening test [8,9,10,11,12,13]. Several studies have shown that the FAST can convert false positive (non-reactive) non-stress tests (NST) to reactive ones and shorten the time duration that a NST needs to be carried out [11,12,13]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
