Tactile hypersensitivity in pre-term newborns
Résumé
For a long time, newborns, and a fortiori preterm ones, have been considered to be devoid of sensory perception and hence of pain perception. However, tactile perception is functional very soon during prenatal development. From 7 weeks post-conception, fetus show withdrawal reflex after a subtle tactile stimulation of the face. From 21 weeks, after the antero-posterior development of the tactile sensitivity, each part of the body reacts to a tactile stimulation. Still, the threshold of tactile sensitivity of premature newborns remains unknown. This study was performed on 10 preterms, born at 31.3 weeks of gestation (±4.7 s.d.) and tested when they had reached the term age (at least 37 weeks), 9 early-term (born at 37-38 weeks of gestation) and 10 full-term (born at 40-41 weeks of gestation) newborns tested between 2 and 4 days of postnatal age. Thirty adults were also tested (28.35 years old ±3.83 s.d.). The stimulation consisted in touching the back of the subject's hand with a 0.008g Von Frey filament. All subjects were tested twice: once using the filament and once using a fake stimulation. We considered as a response any behavioural change occurring within the first second after the stimulation. Preterm newborns showed strong, albeit non-localized, responses. This hypersensitivity was observed in half of the full-term newborns tested but neither in the early-term newborns nor in the adults tested. This study is the first to show a clear reaction to a so subtle stimulation, unperceivable by adults, underlying an exceptional tactile sensitivity in preterm newborns and an important gap between their and our sensory worlds. From birth, the preterm newborn is subjected to numerous tactile stimulation (delivery, nursing care, contacts with social and physical environments). These results open new lines of thoughts about routine practices.