The effect of external stimuli on fetal behaviour.
The sensory receptors of the human fetus and their adequate stimulation are reviewed. Emphasis is put on the two main sensory routes through which the fetus may be stimulated: the hearing and the cutaneous senses. Most experimental and descriptive studies were done in these two well-defined areas. The core of the review deals with the description of sensory stimulation of the fetus as a function of the known behavioral states. It is postulated, and a series of experimental works cited in support, that reactions of the fetus to external stimuli, irrespective of the route through which they are presented, are subject to modulation by these states. It is proposed that an adequate stimulus in the normal, physiological range produces little or almost no effect in deep sleep (state 1 fetal) and does not change this state, whereas an inadequate stimulus which is strong ("painful") produces a definite change in state 1 fetal and is capable of triggering a change from state 1F to 2F (active sleep or rapid-eye-movement sleep).
D000818:Animals; D003080:Cold Temperature; D005260:Female; D005318:Fetal Heart; D005333:Fetus / Q000502:physiology*; D006309:Hearing; D006339:Heart Rate; D006801:Humans; D010812:Physical Stimulation; D011247:Pregnancy; D011984:Sensory Receptor Cells / Q000196:embryology; D012867:Skin / Q000294:innervation; D012903:Smell; D013649:Taste; D014785:Vision, Ocular