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
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mise à jour du
18 avril 2002
 Obstet Gynecol
1995;86:605-608
cas cliniques
 The Application of Color Doppler Technology to the Study of Fetal Swallowing
B Petrikovsky, GP Kaplan, H Pestrak
Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, North Shore University Hospital Cornell University Medical College, Manhasset, New York
 
 

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Swallowing activity develops earlier than sucking in the course of fetal development. The human fetus demonstrates swallowing movements as early as 11 weeks gestation, whereas more complex sucking movements can be identified at 18-20 weeks. Swallowing has been studied electrophysiologically in fetal sheep, which have been documented to swallow 20-200 mL of amniotic fluid (AF) in two to seven separate swallowing episodes over a 24-hour period of observation. Recently, Sherman et al evaluated swallowing in singleton gestations in chronically instrumented ewes, both electromyographically and by assessing esophageal fluid flow. Fetuses swallowed an average of 35+-9 ml/hour during the 12-hour study. Total daily volume of swallowed fluid was 840+- 224 ml.
 
Neurologic control of fetal swallowing included coordinated contractions of the thyroid, nuchal, and thoracic segments of the esophagus, which averaged 43+-3 contractions per hour. Recent advances in ultrasonography have allowed adequate imaging of fetal structures involved in the mechanisrn of swallowing, namely the fetal mouth, tongue, pharynx, larynx, trachea, and esophagus. We present our observations of fetal swallowing obtained by superimposing color-flow Doppler signals on the regular gray-scale sonographic image. Thorough knowledge of the physiology of fetal swallowing may allow us to achieve a better understanding of abnormal swallowing in neurologically impaired fetuses.
 
3D
 
Materials and Methods : A sagittal view through the fetal face and a profile were imaged in ten fetuses at 36-41 weeks gestation. All mothers were referred for fetal assessment, including a biophysical profile, for the following indications: decreased fetal movement in three, previous stillborn in two, suspected postmaturity in five. Studies were performed in the postprandial state at 9 Am and 12 noon in a quiet room with the woman in the lateral recumbent position. All ultrasound examinations were performed using a 3.5-MHz Acuson 128 PX curvilinear probe. All observations were made in the absence of fetal breathing.
 
Fetal lips, mouth, tongue, pharynx, larynx, trachea, and esophagus were surveyed in serial coronal planes. Color-flow Doppler signals were superimposed on each gray-scale image to assess the direction and location of AF flow with respect to anatomic structures of the fetal upper gastrointestinal and respiratory tracts during the act of swallowing. All fetal movements were analyzed by a review of the videotape in slow motion. All neonates were born at term in satisfactory condition. One- and 5-minute Apgar scores were greater than 7 and 9, respectively, in all cases.
 
Results : Two to six sucking movements preceded every swallow in eight of the ten fetuses. The remaining two fetuses exhibited one sucking movement before each swallow. The swallowing process itself was initiated by opening of the fetal mouth and the introduction of AF into the oral cavity. At this stage of swallowing, no active tongue movements were detected. At each such mouth opening, the fetus continued to fill the oral cavity. Minimal spillage of AF back into the amnion was seen. The soft palate superiorly and the tongue posteriorly and inferiorly obstructed the further flow of AF at this stage of swallowing.
 
Low-frequency tongue movements in the caudal direction were associated with further movement of AF toward the pharynx. Elevation of the soft palate and its opposition to the posterior wall of the pharynx were incomplete, as evidenced by a tiny stream of AF directed superiorly to the nasopharynx. A small stream of AF was directed into the trachea as well. Upward movement of the larynx and epiglottic movement were seen next, in association with narrowing of the lumen of the pharynx. These dynamic changes were accompanied by downward flow of AF into the esophagus.
 
Discussion : Previously, we studied the effect of fetal swallowing on the AF index in response to acoustic stimulation and found that AF decreases after extensive fetal swallowing. However, the mechanism of normal fetal swallowing has remained obscure. We report here the use of color Doppler technology to describe the swallowing cycle in a term human fetus. The cornbination of color flow and spectral Doppler analyses was used by Chiba et al ,Isaacson and Birnholz, and Badalian et al to study fetal breathing. They demonstrated a positive correlation between breathing-related nasal peak flow velocity and advancing fetal maturity. Isaacson and Birnholz were able to visualize the oropharynx and observed its rhythmic expansions 200 msec before the onset of inspiration and 100 msec before glottic opening. They also described upward displacement of the larynx and speculated that it was related to fetal swallowing. Fox et al modified the technique of Isaacson and Birnholz by scanning in sagittal and transverse planes of the fetal nose, assessing the perinasal flow using color Doppler technique in fetuses with diaphragmatic hernia. Bowie and Clair observed fetal swallowing and regurgitation in normal fetuses and in those with polyhydramnios. They reported distinct pharyngeal and tongue movements related to swallowing activity. However, the use of grayscale imaging alone did not allow the investigators to follow the movements of an AF bolus at different stages of fetal swallowing.
 
Using a color Doppler technique, we were able to observe a flow of AF through the fetal mouth, oropharynx, pharynx, and esophagus. We were particularly careful to videotape fetal swallowing when there were no fetal breathing movements, in order to avoid potential confusion. The swallowing pattern in a normal fetus near term differs from that in the infant and adult. The three phases of swallowing (oral, pharyngeal, and esophageal) are the same, but the oral and pharyngeal phases appear to be less completely developed. In a mature fetus, two to six sucking movements usually precede the initiation of the oral stage of swallowing, whereas in an adult, during the oral phase the tongue opposes the hard palate to propel a liquid or solid bolus into the oropharynx. The base of the tongue moves upward to the posterior pharyngeal wall to seal off the nasopharynx effectively. In the fetus, tongue opposition to the hard palate is not evident, although AF is propelled by the tongue into the oropharynx. In addition, the oropharynx is not sealed completely, allowing some of the AF to escape into the nasopharynx. The normal pharyngeal stage of swallowing in an adult includes glottal closure to prevent aspiration, and opening of the esophageal sphincter. In the mature fetus, the trachea is not sealed completely by glottal closure and swallowed AF is directed not only into the esophagus, but into the trachea as well.
 
A detailed study of the normal development of swallowing over the course of fetal life may lead to the early identification of potential neonatal swallowing difficulties and may shed further light on the mechanisms of polyhydramnios and oligohydramnios