title: Response of the foetal pupil to vibro-acoustic stimulation: a foetal attention test.
abstract: BACKGROUND
  The iris regulates the intensity of light that stimulates the retina. The pupils dilate also in response to mental activities as sign of attention. We hypothesized that the response of the foetal pupil to vibro-acoustic stimulation (VAS) reflects foetal attention.
  
  
  OBJECTIVE
  To determine whether the changes in the foetal pupil produced by vibroacoustic stimulation is a sign of foetal attention.
  
  
  METHODS
  We studied sonographically the pupils and iris of 151 foetuses between 27 and 41 weeks of gestation, using maximum ultrasonic zoom.
  
  
  METHODS
  160 human foetuses between the 27th and the 41st week of gestation.
  
  
  METHODS
  The diameters of the pupil and iris were compared before and after VAS.
  
  
  RESULTS
  At baseline, the pupils were miotic. We observed a response to VAS, manifest as a prominent pupillary dilatation in all foetuses. At all gestational ages, the percent increase in pupillary diameter was ≥57% (mean 87%; range: 57-135%).
  
  
  CONCLUSIONS
  VAS dilated the foetal pupil. Sonographic assessment of the foetal pupil provided important insights in the development of foetal neurological functions.
authors.affiliation: Unit of Foetal Medicine, Vigo University Hospital Complex, Calle Pizarro, 22. 36204, Vigo, Pontevedra, Spain. carlos.lopez.ramon.y.cajal@sergas.es
authors.forename: Carlos
authors.initials: C
authors.lastname: López Ramón Y Cajal
mesh_terms: D000161:Acoustic Stimulation; D001288:Attention / Q000502:physiology*; D005260:Female; D005333:Fetus / Q000502:physiology*; D006801:Humans; D011247:Pregnancy; D011680:Pupil / Q000502:physiology*; D016216:Ultrasonography, Prenatal