Early Human Development, 18 (1988) 81-93 Elsevier Scientific Publishers Ireland Ltd. 81 EHD 00915 Fetal cardiac and motor responses to octave-band noises as a function of central frequency, intensity and heart rate variability J-P. Lecanueta, C. Granier-Deferre” and M-C. Busnelb aLaboratoire de Psycho-Biologie de I’Enfant* CNRS, UA315 41, rue Gay-Lussac, Paris 75005, and bGroupe G&nPtique, Neurogt%tique et Comportements, UER Biom6dicale. Universitk PARIS V, 45, rue des Saints-P&es, Paris 75006, France Accepted for publication 18 January 1988 Summary Accelerative and decelerative cardiac responses and motor responses (leg movements) of 37-40 weeks (G.A.) fetuses are analyzed as a function of the frequency of three octave-band noises (respectively centered at 500 Hz, 2000 Hz and 5000 Hz) and of their intensity level (100, 105, 110 dB SPL, ex utero), during high (HV) and low (LV) heart rate (HR) variability pattern states. In both states, increasing the frequency and/or the intensity of the acoustic stimulation: (i) increases the ratios and amplitudes of accelerations, and the motor response ratios, (ii) reduces deceleration ratios and motor response latencies. Cardiac and motor reactiveness are higher in HV than in LV with acceleration ratios always greater than motor ones. However, when a high intensity and/or frequency is used, the reactive- ness differences between states disappears. Low intensity and/or frequency stimula- tion levels induce a majority of decelerations. fetus; acoustical stimulation; intensity; frequency; cardiac acceleration; cardiac deceleration; motor response; heart rate variability pattern Introduction Since 1925 [33], human fetal reactiveness to sound has been investigated with loud external stimulations (see Ref. 8). They induce mostly accelerative (or biphasic) heart rate (HR) modifications and fast motor responses, components of the acoustic startle response. 0378-3782/88/$03.50 0 1988 Elsevier Scientific Publishers Ireland Ltd. Published and Printed in Ireland