Effects of vibratory acoustic stimulation on human fetal breathing and gross fetal body movements near term.

Twenty-five pregnant women between 36 and 40 weeks' gestational age were studied to examine effects of a 5-second external vibratory acoustic stimulus on fetal breathing and gross fetal body movement patterns. When the study period was compared with the control period, there was an immediate significant decrease in the incidence of fetal breathing movements that persisted for 1 hour after the stimulus. Moreover the fetal breathing pattern was more irregular for the hour after the stimulus. There was also a significant but delayed increase in the incidence of gross fetal body movements that persisted for 1 hour after the stimulus. We hypothesize that an external vibratory acoustic stimulus causes a change from a state of sleep to a state of wakefulness in near-term healthy fetuses.