EFFICACY AND SAFETY OF FETAL ACOUSTIC STIMULATION TESTING

Objective: The non-stress test (NST) has emerged in many centers as th e primary test for fetal well-being. However, the high percentage of f alsely non-reactive tests has led to prolonged testing time and to mor e invasive forms of evaluation. Fetal acoustic stimulation (FAS) appea rs to hold promise for improving the speed and accuracy of clinical as sessment when using the NST. The purpose of this study was to evaluate the efficacy of using FAS to decrease the number of falsely reactive NSTs and to decrease antenatal testing time. The second purpose was to evaluate the safety of FAS testing using the neonatal brain stem audi tory-evoked response (BAER) test. Methods: Over a 6-month period, 184 patients were randomized to receive either the NST or FAS as the prima ry method of fetal assessment. FAS was performed using an electronic a rtificial larynx applied to the maternal abdomen at a sound intensity level of approximately 80 decibels and a frequency of 85 hertz. Some i nfants receiving in utero stimulation with the artificial larynx were picked to undergo hearing evaluation by BAER testing in the nursery pr ior to discharge. These results were compared to gestational age contr ols from our nursery. Results: Over a 6-month period, 184 patients wer e randomized to receive either the NST or FAS as the primary method of fetal assessment. In the NST group, 10.9% of the tests (27/248) were non-reactive as compared to only 0.7% of the tests (1/134) in the FAS group (P < 0.005). Testing time was also significantly shorter in the FAS group (10.6 minutes versus 8.2 minutes, P < 0.05). BAER testing wa s performed on both ears of 10 infants delivered at 37-41 weeks gestat ional age. Standard waveform analysis for sensorineural hearing loss r evealed no difference between babies of mothers undergoing antepartum assessment with FAS and gestational age controls. Conclusions: FAS tes ting can significantly reduce the number of falsely non-reactive NSTs and thus reduce the number of patients who would otherwise undergo mor e prolonged or invasive forms of monitoring. Testing time is also sign ificantly reduced. Based on the current reference method for evaluatin g neonatal hearing, FAS appears to be a safe and reliable method of an tenatal fetal evaluation.