Auditory evoked response of the human fetus: simplified methodology

The author presents a retrospective study where he analyzes the possibility of using sound-evoked movements of human fetuses to evaluate their conditions in utero. He uses a narrow band stimulator at 1,500 cycles/second at 125 decibels of sound level pressure as five pulsed stimuli lasting two seconds each and one second apart applied to maternal abdomen. Analysis was performed on 2,025 fetal electronic monitoring tests on which 1,626 auditive stimulation were applied. A test was considered positive when sound stimulation evoked no movements or only a slight, slow, not immediate movement was observed by the mother or the professional applying the test. A test was considered negative (fetus in good health) when a fetal immediate sudden, strong, Moro like reaction was observed clinically (starttle reflex). This test produced a sensitivity of 57.35%, greater than any other observed in nonstress cardiotocography. The author suggests this simple, easy-to-apply test should have a place as screening procedure in large populations or where facilities for more complete monitoring are not available. The combination of this simplified auditive stimulation with the conventional auditory evoked response offers better sensitivity and positive predictive values than the largely used non-stress test. In any case it would help in the detection of potential risk cases and should be included as a first simple procedure to be applied to high risk pregnancies.