The relationship between the response to external light stimulation and behavioral states in the human fetus: how it differs from vibroacoustic stimulation.
OBJECTIVE
To determine the effects of external light stimulation on fetal behavioral states and know the difference from those of vibroacoustic stimulation.


METHODS
A flashlight and a vibroacoustic stimulator was applied directly on the maternal abdomen to determine the response of 56 normal fetuses at 36-40 weeks gestation. Fetal heart rate (FHR) and body movements were recorded using an actocardiograph, and fetal eye movements were observed using real-time ultrasonography. Using Nijhuis's criteria, the fetal behavioral states (1F-4F) were determined. FHR acceleration was considered a fetal response to the stimulations.


RESULTS
The lag time between stimulation and fetal response was within 4 s. A positive response rate to the light stimulation was higher at behavioral states 2F (82%) and 3F (83%) than at state 1F (4%). Light stimulation changed the behavioral state of two of the six 3F fetuses (33%) from 3F to 4F. No change of state was observed in fetuses that were in states 1F and 2F. For vibroacoustic stimulation, fetal response was 100% positive and changes of states were observed frequently irrespective of the behavioral state before the stimulation.


CONCLUSIONS
Fetal response to light stimulation is closely connected to fetal behavioral states and may reflect some distinct stages of the sleep-wakefulness cycle.
Kiuchi
M
M
Department of Obstetrics and Gynecology, Tottori University School of Medicine, 36-1 Nishimachi, 683-8504, Yonago, Japan.
Nagata
N
N
Ikeno
S
S
Terakawa
N
N
D000161:Acoustic Stimulation; D001519:Behavior; D005133:Eye Movements; D005260:Female; D005324:Fetal Movement; D005333:Fetus / Q000502:physiology*; D005865:Gestational Age; D006340:Heart Rate, Fetal; D006801:Humans; D008027:Light; D010775:Photic Stimulation; D011247:Pregnancy; D014732:Vibration