Use of sound-elicited fetal heart rate accelerations to assess fetal hearing in the second and third trimester

Abstract

ObjectivesWe previously reported that fetal heart rate (FHR) accelerations could be obtained after fetal sound stimulation. We examined FHR accelerations during 20–37 weeks gestational age (GA) in order to assess the optimal time for the test. MethodsThe fetus was stimulated from the maternal abdomen with pure tone 2000 Hz, 90 dB, 5 s. Changes in the FHR before and after the sound stimulation were measured by a cardiotocometer. ResultsCompared with the positive rate of FHR accelerations at 20–21 weeks GA, significant increases were recognized in 26–27, 28 to 29, 30 to 31, and 34–35 weeks GA. Comparing the positive rate of FHR accelerations between the minimal and moderate variability of FHR baseline, no significant differences were observed at 20–27 weeks GA. On the other hand, at 28–37 weeks GA, the positive rate to detect FHR accelerations due to sound stimulation was 100% in moderate FHR baseline variability. ConclusionConsidering development of human fetal hearing, the method should be performed between 28 and 37 weeks GA and during moderate FHR variability corresponding to active sleep conditions. The method developed in the present study may provide a promising tool for evaluating the fetal hearing.