Related Experiment Video
Updated: Jun 5, 2026
Quantitative Assessment of Cortical Auditory-tactile Processing in Children with Disabilities
Published on: January 29, 2014
Response of the foetal pupil to vibro-acoustic stimulation: a foetal attention test
1Unit of Foetal Medicine, Vigo University Hospital Complex, Calle Pizarro, 22. 36204, Vigo, Pontevedra, Spain. carlos.lopez.ramon.y.cajal@sergas.es
Insights
Vibro-acoustic stimulation (VAS) caused significant pupillary dilation in fetuses, suggesting fetal attention. This sonographic method offers insights into developing fetal neurological functions.
Area of Science:
- Fetal Neurology
- Ophthalmology
- Developmental Biology
Background:
- The iris controls light entering the eye, and pupil dilation can indicate attention.
- Fetal pupil response to external stimuli is not well understood.
Purpose of the Study:
- To investigate if fetal pupil changes in response to vibro-acoustic stimulation (VAS) indicate fetal attention.
- To assess the feasibility of sonographic monitoring of fetal pupil dynamics.
Main Methods:
- Sonographic examination of pupils and irises in 160 fetuses (27-41 weeks gestation).
- Pupil and iris diameters were measured before and after VAS.
- Maximum ultrasonic zoom was utilized for detailed imaging.
Main Results:
- Baseline fetal pupils were miotic (constricted).
- VAS consistently induced significant pupillary dilation in all fetuses studied.
- The mean pupillary diameter increase was 87%, with a range of 57-135% across all gestational ages.
Conclusions:
- Vibro-acoustic stimulation reliably dilates the fetal pupil.
- Sonographic assessment of fetal pupil response is a valuable tool for evaluating fetal neurological development.
- This method provides insights into early neurological function and attention mechanisms in utero.
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.
Aims:
To determine whether the changes in the foetal pupil produced by vibroacoustic stimulation is a sign of foetal attention.
Study Design:
We studied sonographically the pupils and iris of 151 foetuses between 27 and 41 weeks of gestation, using maximum ultrasonic zoom.
Subjects:
160 human foetuses between the 27th and the 41st week of gestation.
Outcome Measures:
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.
