Abstract
Human fetal evoked response to acoustic stimuli was recorded from the abdominal wall of five mothers at the 32th to 38th week of pregnancy. Tone bursts with frequency of 1000Hz, duration of 50m sec, and rise and decay time of 13msec were given every 4 seconds through a bone vibrator attached to the maternal abdominal wall at then nearest place to the fetal ear. The responses were conducted through an active electrode located on the maternal abdominal wall in the vicinity of the fetal vertex and were averaged by a digital computer. The results were as follows:
1) The typical wave form of the response consisted of four prominent deflections: a negative, a positive, a negative and a positive deflection with respective peak latencies of 100 to 150msec, 200 to 300msec, 500 to 600msec and 700 to 800msec.
2) These deflections of the fetal evoked response were considered to correspond to the four components (N1, P2, N2, P3) of the slow “vertex potential” to auditory stimulus in young children.
3) This fetal evoked response could not be recorded from the abdominal wall of non-pregnant woman or case without tonal stimulation.
