Abstract
: The capacity of 4D-US to evaluate complex
facial expressions allows to recognize a common
behavior, yawning. Although remarkably little
interest has been paid to yawning in research
and medical practice, even though it is an
everyday phenomenon, we submit an original
interpretation on the basis of knowledge derived
from phylogeny and ontogeny. As a flip-flop
switch, the reciprocal interactions between
sleep and wake promoting brain regions allow the
emergence of distinct states of arousal. By his
ontogenical links with REM sleep, yawning
appears as a behavior which procures an
arousal's reinforcement throught the powerful
stretch and the neuromuscular rewiring induced.
Yawning indicates an harmonious progress in the
development of both the brainstem and the
peripheral neuromuscular function, testifier the
induction of an ultradian rhythm of vigilance.
The lack of fetal's yawn as of swallowing,
associated or not with retrognathia, may be a
key to predict a brainstem's dysfunction after
birth.
Fetal swallowing movernents in utero have
been well documented and are thought to
contribute to the dynamic balance of amniotic
fluid volume, especially in the latter half of
pregnancy. The facial coronal view is an
important tool in evaluating facial anatomical
integrity. This view dernonstrates orbits,
ocular lenses, eyelids, nose, and lips. In this
scanning plane, movements of the tongue, chewing
and wide opening of the mouth have been noted.
Recently, while scanning a fetus at 20 weeks in
the coronal plane, we noted a fetal yawning
movement. The fetal mouth, previously closed,
opened widely and remained so for 2 to 3 minutes
with concomitant bilateral extension of the
fetal upper extremities and flexion of the fetal
head, resembling a yawning response, markedly
different than a brief swallowing episode.
Yawning is a complex arousal defense reflex
located in the reticular brain stem with a
peripheral and central arch. Currently,the
etiology or the underlying stimulus evoking
yawning is not known. The previous hypothesis of
yawning being facilitated by higher than normal
levels of C02 or lower than normal levels Of 02
blood levels has been rejected? Our above case
suggests yawning is an earlyappearing mechanism
functioning in utero at 20 weeks gestation.
References
Romero R, Pilu G, Jeanty P, et al The Face
in Prenatal Diagnosis of Fetal Anomalies.
Norwalk, CT, Appleton & Lange, 1988, p
81
Askenasy
JJ Is yawning an arousal defense reflex? J
Psychol 123:609, 1989
B Petrikovsky, GP Kaplan, H Pestrak
Gynecol 1995;86:605-8
Robert
S Egerman, Donald S Emerson
(University of tennesse Memphis)
The New England Journal of Medecine
vol 335, n°20, p1497 (photo
ci-contre)
Fetal facial expressions are
sometimes seen during ultrasonography.
This yawning fetus studied at 34 week's
gestation was born vigorous and healthy
at term.
Brian
McManus, P Devine, R
Brandstetter The N England J of
M vol 335, 1997, n°18, p1329
Regarding the interpretation of the
image showing an ultrasonogram in which
a 34 week-old fetus is repeorted to be
yawning, the literature fails to define
in yawning in a fetus, with the result
that far too many interpretations of
open mouths as yawns have been
accepted. The range of variation
includes, for example, a single,
continuous opening of the mouth lasting
three minute and a set of five
repetitive openings of the mouth for
four to six seconds each.There is also
a discrepancy in the use of the
anatomical criterion of retraction of
the tongue to characterize the fetal
yawn, whereas in yawning adults, the
tongue is extended. Furthermore, we
question the validity of the claim that
such "a rarely observed" event is not
just a reflex related to the swallowing
of amniotic fluid and prolonged by
chance alone.
Finally, if the assessment is based
on accepted models in adults, there is
no physiologic reason why a fetus
should yawn. Doppler studies during
yawning have shown no hypoxia; yawning
confers no protection against
atelectasis in a fluid-filled lung;
because infants with anaencephaliy have
been shown to yawn, the action cannot
be attributed to boredom and if there
is is a need to yawn, the reported
repetitive nature of the action appears
to signify an inability to compensate
for that need.
Masuzaki
H Color Dopplerimaging of foetal
yawning Ultrasound in obstetric
"&"gynecolgy 8(5)355-6 Nov
1996
The authors reply
:
Although we are surprised that the
glimpse of quiet, gentle act has provoked
such a strong response, we recognize that
reviewing a single static image may
produce a skeptical response. Anyone
involved with ultrasonography, however,
recognizes tht it is a dynamic method, and
the real-time viewing of a yawn in process
is much more compelling and less open to
alternative interpretations. Limitations
of publishing technology prevent us from
sharing the full experience with readers.
Although fish, tortoises and mammals yawn,
we cannot explain why human fetus would
yawn. Behaviour observed in utero,
including breathing, yawning, and the
startle response, serves as a continuum to
the activity shown in a newborn infant. It
is unlikely that on emmerging from the
birth canal, an infant undergoes a
neuromuscular rewiring. The yawn, a
rudimentary reflex, apparears to have at
best an obscure pupose, if any. Perhaps,
as a paralinguistic communication, it
signifies a time foor a group members to
rest.
