Vibratory acoustic stimulation and fetal gasping

OBJECTIVE: Vibratory acoustic stimulation (VAS) has been used to shorten the duration of antepartum fetal heart rate monitoring. Questions have been asked regarding the possible effects of VAS on the fetus. VAS was used to investigate whether the acute effect of VAS is associated with gasping in the normal fetus. STUDY DESIGN: Thirty-seven normal patients at 37-42 weeks' gestation with singleton fetuses were studied. All had normal amniotic fluid volume on ultrasound. These 37 subjects had a five-minute baseline sonographic assessment of fetal breathing and body movements. A fetal gasp was defined as an isolated, slow, irregularly occurring, deep, inspiratory- type movement, or series of them, of the chest and abdomen. Three-second VAS was then delivered with an artificial larynx placed directly over the fetal head. Fetal breathing, body and gasping movements were assessed at the time of this stimulus. RESULTS: A significant increase in fetal body movements (P < .001), a significant decrease in fetal breathing (P < .003) and absence of gasping movements were noted. CONCLUSION: The results suggest that gasping does not occur in response to VAS in the normal, term fetus.