This study compared fetal response to musical stimuli applied intravaginally (intravaginal music [IVM]) with application via emitters placed on the mother’s abdomen (abdominal music [ABM]).
Responses were quantified by recording facial movements identified on 3D/4D ultrasound.
One hundred and six normal pregnancies between 14 and 39 weeks of gestation were randomized to 3D/4D ultrasound with: (a) ABM with standard headphones (flute monody at 98.6 dB); (b) IVM with a specially designed device emitting the same monody at 53.7 dB; or (c) intravaginal vibration (IVV; 125 Hz) at 68 dB with the same device. Facial movements were quantified at baseline, during stimulation, and for 5 minutes after stimulation was discontinued. In fetuses at a gestational age of >16 weeks, IVM-elicited mouthing (MT) and tongue expulsion (TE) in 86.7% and 46.6% of fetuses, respectively, with significant differences when compared with ABM and IVV (p = 0.002 and p = 0.004, respectively). There were no changes from baseline in ABM and IVV. TE occurred ≥5 times in 5 minutes in 13.3% with IVM. IVM was related with higher occurrence of MT (odds ratio = 10.980; 95% confidence interval = 3.105–47.546) and TE (odds ratio = 10.943; 95% confidence interval = 2.568–77.037). The frequency of TE with IVM increased significantly with gestational age (p = 0.024).
Fetuses at 16–39 weeks of gestation respond to intravaginally emitted music with repetitive MT and TE movements not observed with ABM or IVV.
Our findings suggest that neural pathways participating in the auditory–motor system are developed as early as gestational week 16. These findings might contribute to diagnostic methods for prenatal hearing screening, and research into fetal neurological stimulation.