Le bâillement, du réflexe à la pathologie
Le bâillement : de l'éthologie à la médecine clinique
Le bâillement : phylogenèse, éthologie, nosogénie
 Le bâillement : un comportement universel
La parakinésie brachiale oscitante
Yawning: its cycle, its role
Warum gähnen wir ?
Fetal yawning assessed by 3D and 4D sonography
Le bâillement foetal
Le bâillement, du réflexe à la pathologie
Le bâillement : de l'éthologie à la médecine clinique
Le bâillement : phylogenèse, éthologie, nosogénie
 Le bâillement : un comportement universel
La parakinésie brachiale oscitante
Yawning: its cycle, its role
Warum gähnen wir ?
Fetal yawning assessed by 3D and 4D sonography
Le bâillement foetal
mystery of yawning 

mise à jour du
12 décembre 2011
Springer 2010
Development of Normal Fetal Movements
The first 25 weeks of Gestation
Alessandra Piontelli
Departement of maternal/fetal medicine
Clinica Mangigalli
University of Milan Italy


Tous les articles consacrés au bâillement foetal
Fetal yawning: all publications
 Bâillements du foetus: la naissance d'un comportement révélée par l'échographie 4D
Fetal yawning : a behavior's birth with 4D US revealed
Video de bâillement foetal à 23 semaines en Echo 4D
autres photos de bâillements foetaux
Video de bâillement foetal à 13 semaines en Echo 4D
Sonography Edited by: Kerry Thoirs
Fetal Yawning Olivier Walusinski
Chapter 18 Pages 325-332
Development of Fetal Yawn Compared with Non-Yawn Mouth Openings from 24-36 Weeks Gestation. Reissland N
Seemingly Trivial Fetal Motions: Yawning and Hiccups. Piontelli A
According to Dorland's Medical Dictionary, "A yawn is a deep, involuntary inhalation with the mouth widely open, often accompanied by the act of stretching". Yawning is composed roughly of an active wide opening of the mouth followed simultaneously by a deep inhalation, a dilatation of the pharynx, larynx and thorax, and by a lowering of the diaphragm. The oral cavity becomes amply visible, the tongue is retroverted, the eyes halfclose, the nostrils dilate, the eyebrows rise and the forehead wrinkles slightly. Finally, the mouth passively closes again with a deep expiration.
Fetuses yawn.
Some authors claim that they do so from 12 weeks. However, we did not detect the first yawns earlier than 15 weeks. Fetal yawns do not correspond completely to the above description. Up until 25 weeks the eyes are kept closed, and the dilation of the nostrils as well as the lowering of the diaphragm are too difficult to evaluate.
At around 25 weeks fetuses open their mouth widely, blink, raise their eyebrows, wrinkle their forehead and retrovert their tongue. Dilation of the larynx, pharynx and thorax have been ascertained in fetal animals such as sheeps.
Yawns last on average 8-10 s and occur principally as occasional and isolated events. However, in three cases (at 20, 21 and 25 weeks respectively), one fetus yawned in a series of five and two in a series of six yawns with an interval of 8-10 s between the closure of the mouth and the next yawn.
Most, but not all yawns emerge before a cycle of rest. However when fetuses start yawning, they stop all previous activities, and only resume any other motion when the yawn or yawns are over.
Yawning fetuses do not display apparent signs of distress. Cerebral blood flows were checked during and immediately after yawning, but these were well within the normal range.
On the whole, we are still far from understanding the functional significance of yawning, whether before or after birth. Nevertheless, one cannot but wonder why fetuses yawn. In life after birth, yawning is mostly connected with tiredness, sleepiness, boredom, irritation, interruption of sleep and rousing. However, yawning can also be related to pleasure and relaxation as well as hunger. It is difficult to ascribe complex emotions such as boredom or irritation to fetuses. Hunger is another stimulus which may hardly be experienced in utero, save perhaps in extreme circumstances. Hedonic feelings are hard to demonstrate at this early stage, too, though fetuses may begin to function on a pleasure/displeasure base. Some motions and positions are "preferred" to others, but one cannot go much further beyond this simple fact. Anyway, even assuming fetuses could begin to experience some form of pleasure or displeasure after the first half 4 pregnancy, why should this be expressed through yawns?
In life after birth yawning has a "contagious", social nature. Seeing someone yawning triggers a yawn. Yawning also has an ideational component as even just thinking of yawning makes one yawn. None of this, however, can be associated with fetal life. Fetuses can hardly be regarded as social beings, though they increasingly prepare to enter a social world. In utero they clearly never see someone yawning, nor were the fetal yawns we studied preceded or followed by their mothers' yawning. All mothers (and fathers) were very attentive and laughed during and after the fetal yawn. It is also difficult to assume that fetuses could have such complex forms of ideation as to think about a yawn, and start yawning as a consequence.
After birth, yawning is not a necessary event, in the sense that it does not invariably accompany any of the above-mentioned states, and displays large variations both within the same individual and amongst different individuals. The same quality of apparent non-necessity applies in fetal life. After birth, frequent yawning is linked with a variety of medical conditions. Neurological conditions are often associated with frequent yawning. Viral infections, diseases directly affecting the trunk or its compression due to intracranial hypertension, diseases of the thalamus, of the region of the hypophysis, brain tumours, cerebral haemorrhage, multiple sclerosis, myasthenia gravis and more are all coupled with excessive yawning. All sorts of non-neurological conditions can also cause excessive yawning. These range from diabetes to profuse bleeding, liver cirrhosis and heart attack. However, nonexcessive yawning is a perfectly normal phenomenon in man during all phases of life, and fetuses can hardly be defined as excessive yawners. Furthermore, all fetuses who yawned were perfectly healthy at birth and at subsequent follow-ups.
Though yawning is readily and easily recognizable at all ages, including the fetal stage, various modes of yawning and their possible significance may change with age. In the neonate, yawning is almost invariably accompanied by stretching. In the adult, stretching especially occurs when yawning is associated with awakening, and as such has been related with a kind of re-setting in motion of the organism after the relative stillness of sleep. In the fetus, some tentative form of stretching can be observed only from 24 to 25 weeks. One or both arms can be slightly stretched outwards and the forearm stretched either upwards or downwards. However, at this stage stretching is barely perceptible.
The neural mechanisms controlling yawning have been to some extent clarified. A primary "yawning centre" is located in the bulbopontine regions of the cerebral trunk. Anencephalic children born with the cerebral hemispheres missing or reduced to small masses attached to the base of the cranium, and without the cerebellum and the flat bones of the skull, yawn and stretch just like all of us. In other words, we don't need a cortex in order to yawn. In man and in some mammals a second pathway is thought to be represented by the ill-defined limbic system, an assemblage of interrelated, phylogenetically old, deep brain structures commonly regarded as involved in emotions, motivation, processing of sensory and motor functions, memory and even cognitive information.
Given its link with sleep, and especially with the transitions between sleep and wakefulness and vice versa, yawning has elicited a special curiosity in those involved in sleep research. The main experts in the field can be considered to be the American psychologist Robert Provine and the neurologist and psychiatrist Piero Salzarulo in Italy.
The association between yawning and sleepiness has been explained by the anatomical proximity between the bulbopontine region involved in yawning and the ascending reticular formation discovered in 1949 by Moruzzi and Magoun. This latter system acts diffusely on the cerebral cortex and activates it, regulating arousal and sleep.
Awakening is very rare before 34-36 weeks, and fetal sleep prior to this age is considered by many to be a preparatory function only akin to sleep. Fetuses do not yawn because they feel sleepy.
Besides in man, yawning is widespread throughout the animal kingdom. Darwin in his famous book The expression of emotions in man and animals mentioned yawns in various species of monkeys, including the baboon, the macaque and the cercopithecus. Following his lead, other scientists have investigated yawning in animals. When monkeys yawn, they display acuminate teeth. "Alpha males" have been found to yawn more frequently not only than females, but also than less high-ranking males. For this reason, this display and consequently yawning have been taken to indicate dominance, aggression and territorial defence.
Besides monkeys and mice, all sorts of animals, including snakes, fish, penguins, crocodiles, and parrots yawn. Given its widespread nature within the animal kingdom, yawning could have different functions in different species.
All sorts of explanations have been given to explain yawning in man, ranging from oxygenation to brain cooling. Yawning has been suggested to foster wakefulness, or to communicate relaxation after a period of high vigilance. By being contagious, yawning indicates empathy, appreciation of other people's behavioural and physiological states. Many more explanations have been offered. However, none of the above could apply to the fetus.
Yawning: a Form of Communicating?
Finally, a few additional words on yawning. Provine, the researcher who studied many of its facets, considered it a facial expression with a communicative function after birth. Jean Piaget was the first to make an important observation in 1951: that children started yawning in response to seeing a yawn only during the 2nd year of life. Subsequently, Provine and Anderson and Meno [271 proved experimentally that contagiousness of yawning did not start reliably in children under 6 years old. This finding aroused a lot of interest from two main points of view. Following the seminal studies of Meltzoff and Moore, it has long been known that newborns are capable of recognizing and imitating most facial expressions. Many scientists wonder why they do not do the same with such a dramatic facial expression as a yawn. Recently, yawning has met with renewed interested linked with studies of mirror neurons and autism.
So-called autistic spectrum disorders are characterized by a more or less profound impairment in communicative capacities and shared social interactions. Autistic individuals have problems in relating to others and in reading other people's emotional states. In particular, they are unable to display empathic reactions when others show pleasure, fear or pain. Empathy is connected with the capacity to recognize, understand and share the emotions of others. A number of anatomical and functional studies all seem to point to disfunctioning of the above-mentioned mirror neuron system in autism. The fetus and the neonate generally are not 'autistic', yet, as Piaget pointed out, they cannot imitate and possibly decode yawns in others.
This is just an hypothesis, but what if one turned the matter round and saw yawning as an - albeit unconscious - form of communicating various states to the caregiver. When mothers see a neonate yawning, they assume, depending on the context, that the child must be sleepy, waking up, or even hungry. In other words, at the neonatal stage yawning could be an important tool for directing the efforts of the caregiver onto "the right track".
Up to 2 years of age, and before they become fully verbal, children need a lot of empathic understanding on the part of those caring for them. Furthermore, sleep and hunger are two basic and vital states. A caregiver can miss many other nuances, but not these vital needs.
Yawning, unlike crying and screaming, elicits empathy and sympathy, not irritation, anxiety or exasperation, thus simplifying the task. Furthermore, in children yawning would not need to be bidirectional. When babies and children are tired, and they communicate this by yawning, the caregiver usually takes the initiative to put them to bed. At such moments they may like to be lulled to sleep, or be read a repetitive story, but clearly are not willing to engage in complex social interactions. On the other hand, though, babies (and young children) are not keen to recognize fatigue or boredom in their caregiver's face when she or he yawns while they may be needing or demanding some action or interaction. As the saying goes, "Children's needs come first". Mother or father may be tired, but still have to prepare some food or be asked to participate in some story-telling or preparatory ritual for sleep.
If this were the case, fetuses yawning in utero would be displaying a preparatory and anticipatory function, helping them to have their vital needs better understood and more easily met by those caring for them after birth.