Obstetrics and gynecology. Childbirth with extension presentation of the fetal head (lecture notes)

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Obstetrics and gynecology. Childbirth with extension presentation of the fetal head (lecture notes)

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Lecture number 11. Childbirth with extensor presentation of the fetal head

There are the following extensor presentations of the fetal head: anterior head, frontal and facial (the parietal region, forehead or face of the fetus, respectively, are facing the entrance to the small pelvis). These presentations are rare. The main causes of extensor presentations include reduced uterine tone, its uncoordinated contractions, underdeveloped abdominals, narrow pelvis, decreased muscle tone of the pelvic floor, too small or, conversely, large fetal sizes, and lateral displacement of the uterus. Childbirth with extensor presentation of the fetal head (anterocephalic, frontal and facial) are pathological.

Anterior presentation of the fetus (first degree of extension). In this case, the large fontanel is a wire point, the head with a straight size passes the plane of the small pelvis. The direct size is the distance from the glabella to the outer protrusion of the back of the head (12 cm).

frontal presentation characterized by the fact that the wire point is the forehead. The head passes all the planes of the pelvis with a large oblique size. This is the largest size (from the chin to the outer occipital protrusion), it is 13-13,5 cm.

Facial presentation of the fetus is the third degree of extension. With this type of presentation, the wire point is the chin. The head passes the birth canal in a vertical size (from the hyoid bone to the middle of the large fontanel, which is 9,5-10 cm).

extensor presentation include five main stages of the mechanisms of childbirth.

The first moment is the extension of the head, the degree of which is determined by the presentation variant.

The second point is the internal rotation of the head with the formation of a rear view (the back of the head is located in the sacral cavity).

The third moment is the flexion of the fetal head after the formation of a fixation point at the lower edge of the pubic symphysis. With an anterior presentation, it is the forehead, with a frontal presentation it is the region of the upper jaw, with a facial presentation it is the hyoid bone. During the third moment of the mechanism of childbirth with facial presentation, the head is born.

The fourth moment in frontal and frontal presentation is the extension of the head after fixing the back of the head at the top of the coccyx.

The fourth moment (with facial presentation) and the fifth moment (with frontal and frontal presentations) include the internal rotation of the shoulders and the external rotation of the head.

With an anterior presentation, the fetal head becomes brachycephalic as a result of the configuration, i.e., elongated towards the crown. In frontal presentation, the head is extended towards the forehead. With facial presentation, the lips and chin of the fetus are extended.

With extensor cephalic presentations, other anomalies of insertion of the head are also possible: high straight standing of the head, low (deep) transverse standing of the head, asynclitism.

The diagnosis of anterocephalic presentation of the fetus is carried out using data from a vaginal examination: the large and small fontanelles of the fetal head are at the same level or the large one is lower than the small one. Childbirth occurs through the natural birth canal, their management is expectant. If there are indications (fetal hypoxia, spasm and rigidity of the muscles of the birth canal) and appropriate conditions, it is possible to carry out surgical intervention in the form of obstetric forceps or the use of a vacuum extractor. Protection of the perineum of the woman in labor is carried out, as in the case of occipital presentation. A caesarean section is necessary if the size of the pelvis of the woman in labor and the head of the fetus do not match.

frontal presentation the fetus is observed in most cases in the form of a transitional state to facial presentation. Diagnosis of frontal presentation is based on auscultation of fetal heart sounds, external obstetric and vaginal examinations. With frontal presentation, the fetal heartbeat is better heard from the side of the breast. During an external obstetric examination, on one side of the presenting part of the fetus, a sharp protrusion (chin) is probed, on the other, the angle between the back and the back of the head. The diagnosis is determined by vaginal examination. At the same time, the frontal suture, the anterior edge of the large fontanel, the superciliary arches with eye sockets, and the nose of the fetus are determined. Childbirth in a natural way is possible only with a small size of the fetus. In other cases, with a frontal presentation, a caesarean section is necessary if in the next 2 hours the frontal presentation does not turn into a facial or flexion presentation.

Facial presentation of the fetus can be diagnosed by external obstetric examination. In this case, the dimensions of the head are larger than with the occipital presentation. In cases of severe swelling of the fetal face, vaginal examination is sometimes erroneously diagnosed as breech presentation. The differential diagnosis is based mainly on the determination of fetal bone formations. With facial presentation, the chin, superciliary arches, and the upper part of the orbit are palpated. With breech presentation, the coccyx, sacrum, ischial tubercles are determined. In cases of careless vaginal examination, damage to the eyeballs and mucous membrane of the oral cavity of the fetus is possible. If a vaginal examination reveals that the chin is turned backwards, then natural childbirth is not possible. In such cases, with a live fetus, a caesarean section is performed. If the fetus is not viable, then resort to perforation of the head. If, with the front presentation of the fetus, the chin is turned forward, childbirth takes place spontaneously.

Author: Ilyin A.A.

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