Color Doppler ultrasound has been widely
used to study arterial and venous circulation in
fetuses. Moreover, this technique has recently
been applied to the observation of fetal nasal
and buccal fluid flow. In this report, we
describe fetal yawning as revealed by color
Doppler ultrasound.
Case report : A 26-year-old Japanese
woman underwent ultrasonographic examination for
fetal growth at 30 weeks' gestation. The
examination was performed using an ALOKA SSD2000
ultrasound system with color-flow and spectral
Doppler analysis capabilitles. A single fetus in
the vertex presentation showed no structural
anomalies and normal amniotic fluid volume;
fetal growth was consistent with dates. At the
time of facial examination, fetal yawning
happened to be observed over a 5-s period. The
full extent of fetal yawning was recorded ou an
attached two-dimensional Cine Mode Display
(ALOKA) in order to analyze the fetal nasal and
buccal fluid flow associated with fetal mobihty
at a precise moment in time.
For the first 3 s, a slow opening of the
mouth was followed by maintenance of the open
position without any recognizable color in the
nasal or buccal area. In the next phase (3-5 s),
a red-colored jet flowing from the nostrils
appeared, gradually increasing with the
sustained wide opening of the mouth, ending with
a buccal fluid flash associated with the quick
closure of the mouth.
Discussion : Yawning is a complex
involuntary behavioral reflex induced by hunger,
sleepiness or boredom. Its mechanism and
functional role are not entirely known. Its
behavioral aim seems to be an arousal defense
reflex with subserving reversal of brain
hypoxia. Notably, yawning can be used as a
functioning index of the dopaminergic system in
vivo in the human being.
The yawning motion can rarely be observed in
the human fetus. According to de
Vries and colleagues, fetal yawning is a
non-repetitive movement similar to the yawn
observed after birth: prolonged wide opening of
the jaws followed by quick closure. It is
initially observed at around 11 weeks and
follows no particular gestational age-related
pattern. Sepulveda and
Mangiamarchi documented repetitive fetal
yawning movements in detail in a 27-week fetus.
They noted that several yawning movements
occurred and that each individual sequence was
observed for only a very short period of time,
ranging from 4 to 6 s. We confirm their
observation regarding the duration of yawning,
but in our case, a single non-repetitive yawning
movement was seen.
Color Doppler is able to visualize the
presence of flow in the nasal fossa, mouth,
pharynx, trachea and esophagus. This technique
bas been used to predict fetal upper respiratory
tract function and diagnose fetal cleft palate.
In the present case we confirmed that fetal
yawning was accompanied by a fluid movement
between the amniotic cavity anf the fetal
airway. Fertal jaw movements with prolonged
opening of the mouth were fare more commonly
observed than yawns. We assume, therefore, that
color Dopller imagung of the fetal nasal and
buccal area can be used to distinguish between
fetal yawning and fetal jaw movement.
