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27 janvier 2002
Ultrasound Obstet Gynecol
1995; 5; 57-59
Fetal Yawning
W Sepulveda, M Mangiamarchi
Centre for fetal care, Queen Charlotte's and Chelsea Hostpital London
 
Video de bâillement foetal à 23 semaines en Echo 4D
Video de bâillement foetal à 13 semaines en Echo 4D
Fetal yawning in utero at 20 weeks gestation
Sherer DM, Smith SA, Abramowicz JS. J.Ultrasound Med 1991 Feb;10(2):68
Fetal yawning : a behavior's birth with 4D US revealed
 Bâillements du foetus: la naissance d'un comportementrévélée par l'échographie 4D Dr O.Walusinski
 
INTRODUCTION The advent of real-time ultrasonography has allowed the observation and further characterization of several aspects of behavior in the human fetus, including body extremity movements, breathing movements, stretches, startles, hiccups, eye movements, jaw movements, sucking and swallowing, head to face contact, and head rotation, anteflexion and retroflexion.
Fetal yawning, one of the most uncommon behavioral, states in hurnan fetuses, can be observed incidentally, during ultrasonographic examination of the fetal face during the second and third trimeisters. In this report, we describe in detail a fetal yawning pattern in a 27-week fetus. This observation provides chronological timing and expands previous observations of this complex involuntary reflex in utero.
 
fetal yawn
CASE REPORT
A 25-year-old woman underwent ultrasonographic evaluation for fetal growth at 27 weeks because of uterine size and dates discrepancy. High-resolution ultrasonographic examination (Acuson 128XP/ 10, Acuson, CA) revealed a single fetus in cephalic presentation with biometry consistent with dates. There were no fetal structurai anomalies, the amniotic fluid was normal, and color Doppler examination demonstrated normal impedance indices in both. the umbilical and middle cerebral arteries. During focused examination of the face, the fetus clearly yawned several times. Five yawning movements in total, all similar to those seen in infants, were observed over a 7-min period of time. They consisted of a slight extension of the head, followed by progressive and wide opening of the mouth with simultaneous retraction of the tongue, sustaining wide opening of the mouth for a fraction of a second, and a return to the resting position with closed mouth and flexed head. All five complete sequences observed vere taped in a video cassette recorder, model AG-7/350 (Panasonic, Tokyo) and 2-D Cine Option Display (Acuson) used for subsequent analysis of timing. Each yawn lasted for 4-6 s, the intervals between yawns being 138. 42, 195 and 21 s. Since we were imaging the fetal profile, a simultaneous view of the upper extremities and thoracoabdominal region was not possible and therefore simultaneous stretching of the arms and fetal breathing if present, were not documented. At 38 weeks, an elective Cesarean section was performed because of previous Cesarean delivery, with delivery of a healthy fernale infant weighing 2890 g with Apgar scoresof 8 and 10 at 1 and 5 min, respectively, and arterial and venous cord pH of 7.294 and 7.346 respectively. Follow-up to 2 months has been normal.
 
DISCUSSION
Yawning is a universally well known, but poorly understood, physiological reflex present in almost all mammals, consisting of breathinig through the mouth and nose with a long inhalation with the mouth wide open, followed by a slow exhalation. Although it can be induced by several physiological processes, such as hunger, fatigue, sleepiness, boredom and drowsiness, a number of neurological disorders and drugs can also trigger this reflex. The physiological function and neuroanatomical pathways involved in yawning are unknown. It is therefore not surprising how little is known about this reflex in the human fetus. According to de Vries and coworkers and Roodenburg and colleagues isolated episodes of fetal yawning can occasionally be observed during both the first and the second half of normal pregnancy, with the f irst evidence at 11 weeks. It has also been shown that in terrn human fetuses, yawning occurs predominantly during the active sleep (2F) and not during the quiet sleep (1F) behavioral state. However, since fetal movements of the jaw are far more common than yawns throughout pregnancy, it is possible that some of the movements. observed by these investigators might have represented prolonged opening of the mouth rather than yawning. Sherer and associates described in detail a single yawning movement in a 20 week fetus; they observed that the fetal mouth, previously closed,opened widely and remained so for 2 to 3 minutes'in association with simultaneous extension of the fetal arms and flexion of the fetal head. We cannot confirm their observation regarding the duration of the yawn or the number of yawns,since in our case several yawning movements were seen and each individual sequence was observed for only a very short period of time, ranging from 4 to 6 s. A possible explanation for repetitive yawning in our case could be that the observation was made in a transition between one behavioral state and another, i.e. just before or after the active sleep (2F). behavioral state, but this needs to be proved. The physiological role of yawning during intrauterine life remains speculative. It has been proposed that yawning is a complex arousal defence mechanism. the center of which is located in the reticular brainstem, and its function is to reverse brain hypoxia and improve brain oxygenation. However, its role for only primary respiratory purposes has been questioned. In our case, fetal hypoxia was ruled out by Doppler study. In addition, fetal fatigue or boredom are highly unlikely.A respiratory function is less probabble, since the surrounding environment is liquid rather than gaseous, as in the case of, extrauterine life. However, since a forced inspiration is a critical component of yawning, a potential role for expanding fetal terminal alveoli by the inspired fluid is possible consistent with the hypothesis that yawning may serve as a mechanism to protect against alveolar collapse in extrauterine life.