Biomechanism of labor in anterior and posterior occiput presentation. Principles of conducting the I stage of childbirth. During the first stage of labor, two phases are distinguished

BIOMECHANISM OF DELIVERY IN ANTERIOR VIEW OF OCCIPULAR PRESENTATION

The first moment is flexion of the head.

It is expressed in that cervical part the spine is bent, the chin is approaching chest, the back of the head drops down, and the forehead lingers over the entrance to the small pelvis. As the occiput descends, the small fontanel is set below the large one, so that the leading point (the lowest point on the head, which is located on the wire midline of the pelvis) becomes a point on the swept seam closer to the small fontanel. In the anterior view of the occipital presentation, the head is bent to a small oblique size and passes through it into the entrance to the small pelvis and into the wide part of the small pelvic cavity. Consequently, the fetal head is inserted into the entrance to the small pelvis in a state of moderate flexion, synclitically, in transverse or in one of its oblique dimensions.

Second moment - inner turn heads (correct).

The fetal head, continuing its translational movement in the pelvic cavity, encounters resistance to further advancement, which is largely due to the shape of the birth canal, and begins to rotate around its longitudinal axis. The rotation of the head begins when it passes from the wide to the narrow part of the pelvic cavity. At the same time, the back of the head, sliding along the side wall of the pelvis, approaches the pubic joint, while the anterior section of the head departs to the sacrum. The sagittal suture from the transverse or one of the oblique dimensions subsequently passes into the direct size of the exit from the small pelvis, and the suboccipital fossa is established under the pubic joint.

The third moment is the extension of the head.

The fetal head continues to move through the birth canal and at the same time begins to unbend. Extension at physiological childbirth occurs at the exit of the pelvis. The direction of the fascio-muscular part of the birth canal contributes to the deviation of the fetal head towards the womb. The suboccipital fossa abuts against the lower edge of the pubic articulation, a point of fixation, support is formed. The head rotates with its transverse axis around the fulcrum - the lower edge of the pubic articulation - and within a few attempts it is completely unbent. The birth of the head through the vulvar ring occurs with a small oblique size (9.5 cm). The back of the head, crown of the head, forehead, face and chin are born in succession.

The fourth moment is the internal rotation of the shoulders and the external rotation of the fetal head.

During the extension of the head, the fetal shoulders have already inserted into the transverse dimension of the entrance to the small pelvis or into one of its oblique dimensions. As the head follows the soft tissues of the pelvic outlet, the shoulders move in a helical fashion along the birth canal, that is, they move down and at the same time rotate. At the same time, with their transverse size (distantia biacromialis), they pass from the transverse size of the small pelvic cavity into an oblique one, and in the plane of the exit of the small pelvic cavity into a straight size. This rotation occurs when the fetal body passes through the plane of the narrow part of the pelvic cavity and is transmitted to the born head. In this case, the nape of the fetus turns to the left (in the first position) or right (in the second position) thigh of the mother. The anterior shoulder now enters under the pubic arch. Between the anterior shoulder at the place of attachment of the deltoid muscle and the lower edge of the symphysis, a second point of fixation, support is formed. Under the action of labor forces, the fetal body is bent into thoracic region spine and the birth of the shoulder girdle of the fetus. The anterior shoulder is born first, while the posterior one is somewhat delayed by the coccyx, but soon bends it, protrudes the perineum and is born above the posterior commissure during lateral flexion of the body.

BIOMECHANISM OF DELIVERY IN POSTER VIEW OF OCCIPULAR PRESENTATION

With occipital presentation, regardless of whether the occiput at the beginning of labor is turned anteriorly, to the womb or backwards, to the sacrum, by the end of the period of exile, it is usually set under the pubic joint and the fetus is born in 96% in the anterior view. And only 1% of all occipital presentation the baby is born in the back.

At vaginal examination determine a small fontanel at the sacrum, and a large fontanelle at the bosom. The biomechanism of childbirth in the posterior view consists of five moments.

The first moment is the flexion of the fetal head.

In the posterior view of the occiput presentation, the sagittal suture is set synclitically in one of the oblique dimensions of the pelvis, in the left (first position) or in the right (second position), and the small fontanelle is turned to the left and posteriorly, to the sacrum (first position) or to the right and posteriorly, to sacrum (second position). The bending of the head occurs in such a way that it passes through the plane of entry and the wide part of the cavity of the small pelvis with its average oblique size (10.5 cm). The leading point is the point on the swept seam, located closer to the large fontanel.

The second point is an internal incorrect turn of the head.

An arrow-shaped seam of oblique or transverse dimensions makes a turn of 45 ° or 90 °, so that the small fontanel is behind the sacrum, and the large fontanel is in front of the bosom. Internal rotation occurs when passing through the plane of the narrow part of the small pelvis and ends in the plane of the exit of the small pelvis, when the swept suture is installed in direct size.

The third point is further (maximum) flexion of the head.

When the head approaches the border of the scalp of the forehead (point of fixation) under the lower edge of the pubic articulation, it is fixed, and the head makes further maximum bending, as a result of which its occiput is born to the suboccipital fossa.

The fourth moment is the extension of the head.

A fulcrum (anterior surface of the coccyx) and a fixation point (suboccipital fossa) were formed. Under the influence of generic forces, the head of the fetus makes an extension, and from under the womb appears first the forehead, and then the face facing the bosom. In the future, the biomechanism of childbirth occurs in the same way as in the anterior form of the occipital presentation.

The fifth moment is the external rotation of the head, the internal rotation of the shoulders.

Due to the fact that the biomechanism of labor in the posterior occipital presentation includes an additional and very difficult moment - the maximum flexion of the head - the period of exile is delayed. It requires additional work uterine muscles and abdominals. soft tissues The pelvic floor and perineum are subject to severe stretching and are often injured. Prolonged labor and high blood pressure from the side of the birth canal, which the head experiences at its maximum flexion, often leads to fetal asphyxia, mainly due to the disturbed cerebral circulation.

During childbirth, the fetus passes to the exit from the birth canal, performing translational and rotational movements. The complex of such movements is the presentation of the fetus, which largely determines the complexity of childbirth. More than 90% of cases are occipital presentation of the fetus.

Biomechanism in nulliparous

According to studies, in primiparas, the head moves forward a little during pregnancy. The degree of this progress depends on the ratio of the size of the fetal head and the mother's pelvis. For some, the fetus stops its movement at the entrance, and for some, already in the expanded part of the cavity. When labor begins, the head resumes its advancement when the first contractions appear. If the birth canal interferes with the progress of the fetus, then the biomechanism of childbirth in the anterior view of the occipital presentation occurs in the area of the pelvis where the obstacle is encountered. If the birth proceeds normally, then the biomechanism turns on when the head passes the border between the wide and narrow parts of the pelvic cavity. To cope with the obstacles that have arisen, uterine contractions alone are not enough. Attempts appear, pushing the fetus along the way to the exit from the birth canal.

In most cases, the biomechanism of labor in the anterior occipital presentation is activated at the stage of expulsion, when the head passes into the narrow part of the pelvic cavity from the wide one, although in primiparous everything can begin at the moment of disclosure, when the fetal head is in the entrance.

During the process of expulsion of the fetus, the fetus and uterus are constantly interacting with each other. The fetus tries to stretch the uterus in accordance with its shape and size, while the uterus tightly covers the fetus and amniotic fluid, adapting it to its shape. As a result of such actions fertilized egg and the entire birth canal achieve the most complete correspondence to each other. So there are prerequisites for the expulsion of the fetus from the birth canal.

Division by moments

The biomechanism of childbirth in the anterior view of the occipital presentation is conditionally divided into four points:

head flexion;
its inner turn;
extension of the head;
internal rotation of the trunk combined with external rotation of the head.

moment one

Flexion of the head consists in the fact that under the influence of intrauterine pressure cervical region the spine bends, bringing the chin closer to the chest, and lowering the back of the head down. In this case, the small fontanel is located below the large one, gradually approaching the wire line of the pelvis, and this part becomes the part of the head located below everything.

The benefit of this flexion is that it allows the head to overcome the pelvic cavity with smallest size. The straight size of the head is 12 cm, and the small oblique resulting from flexion is 9.5 cm. True, during the normal course of childbirth, there is no need for such a strong bending of the head: it bends as much as it needs to pass from wide to narrow pelvic cavity. Maximum flexion of the fetal head is required only in situations where the birth canal is not wide enough to allow the head to pass through. This happens when the pelvis is too narrow, and also in the case of posterior occiput presentation.

Flexion is not the only movement of the fetus in this moment of the biomechanism of labor. At the same moment, the head occurs through the birth canal, and after the end of bending, its internal rotation begins. So at the first moment of the biomechanism of childbirth, there is a combination of translational movement with flexion and rotation. However, since the most pronounced movement is the flexion of the head, the name of the first moment reflects this fact.

moment two

Internal rotation of the head is a combination of its translational movement with internal rotation. It begins when the head is bent and settled at the entrance to the small pelvis.

The fetal head, moving progressively in the pelvic cavity, encounters resistance to further movement and begins to rotate around the longitudinal axis. There is a kind of screwing of the head into the pelvis. This occurs most often when it passes from a wide to a narrow part of the pelvic cavity. The back of the head slides along the wall of the pelvis, approaching. This moment can be fixed by watching how the position of the swept seam changes. Before turning, this suture is located in the small pelvis in a transverse or oblique size, and after turning it is located in a direct size. The end of the rotation of the head is marked when the sagittal suture is established in a straight size, and the suboccipital fossa assumes a position under the pubic arch.

Moment three

Extension of the head. The head continues to move along the birth canal, gradually beginning to unbend. In normal delivery, extension is performed at the exit of the pelvis. The back of the head comes out from under the pubic arch, and the forehead protrudes beyond the coccyx, protruding the back and front of the perineum in the form of a dome.

The suboccipital fossa rests on the lower edge of the pubic arch. If at first the extension of the head was slow, at this stage it accelerates: the head unbends literally in a few attempts. The head penetrates through the vulvar ring along its small oblique size.

In the process of extension, the crown, frontal region, face and chin appear in turn from the birth canal.

Moment Four

External rotation of the head with internal rotation of the body. While the head follows the soft tissues of the pelvic outlet, the shoulders screw into the pelvic canal. The born head receives the energy of this rotation. At this point, the back of the head turns towards one of the mother's thighs. The front shoulder comes out first, followed by slight delay due to the bending of the coccyx, the back shoulder is also born.

The birth of the head and shoulders sufficiently prepares the birth canal for the appearance of the rest of the body. Therefore, this step is quite easy.

The considered biomechanism of labor in the anterior occipital presentation for primiparous is completely true for multiparous. The only difference is that in those giving birth again, the beginning of the biomechanism falls on the period of exile, when the waters broke.

Actions of obstetricians

In addition to the biomechanism, it is necessary to use obstetric assistance in childbirth.

You can't rely on nature for everything. Even if a woman in labor has a relatively regular birth in the occipital presentation, the help of an obstetrician may be needed.

First moment. Protection of the perineum, preventing premature extension. Palms need to hold the head, preventing movement during attempts and increasing flexion. It is necessary to strive to ensure that the bending is not maximum, but such that it is genetically necessary. There is no need to intervene unless absolutely necessary. The child is usually able to adapt himself to birth canal. It is the obstetric benefit during childbirth that causes many complications, and not the childbirth itself. More often, the child is injured not from the perineum of the woman in labor, but from the hands of the midwife protecting the perineum.
second moment- in the absence of attempts to remove the head from the genital slit. If the head comes out at the maximum of attempts, it strongly presses on the genital slit.

This is the order. With the completion of the attempt, the vulvar ring is gently stretched with fingers right hand over the birthing head. Stretching is interrupted with the beginning of a new attempt.

These actions, aimed at obstetric benefits, must be alternated until the head of the parietal tubercles approaches the genital opening, when the compression of the head increases and the stretching of the perineum increases. As a result, the risk of injury to the head of the fetus and the woman in labor increases.

Third moment- minimize the tension of the perineum to increase the compliance of the penetrating head. The obstetrician gently presses with his fingertips on the tissues surrounding the genital opening, directs them towards the perineum, which reduces its tension.

Fourth moment- adjustment of pushing. The time of appearance of the parietal tubercles of the head in the genital gap increases the risk of perineal rupture and traumatic compression of the head.

Just as great danger bears complete cessation pushing Important role breath plays in it. The mother is told to breathe deeply and often. open mouth to ease tension. When the need arises in an attempt, the woman in labor is forced to push a little. By the method of initialization and termination of attempts, the midwife controls the birth of the head at the most crucial time.

Fifth moment- the appearance of the shoulders and torso. After the head comes out, the woman in labor needs to push. Shoulders are born, as a rule, without the help of an obstetrician. If this does not happen, the head is captured by hand. The palms of the hands touch the temporo-buccal regions of the fetus. The head is first pulled down until one of the shoulders appears under the pubic arch.

Next, the head is taken with the left hand and lifted up, and the right crotch is shifted from the back shoulder, which is carefully removed. Having freed the shoulder part, lift the torso up by the armpits.

In some cases, to prevent intracranial injury a perineotomy is performed if the perineum is unyielding.

Complications

Although anterior occiput delivery routinely demonstrates a biomechanism, complications can occur. Strongly affects the possibility of a successful delivery. Difficult births occur if the woman in labor has a narrow pelvis. This pathology is quite rare. It serves as a reason for the decision to carry out a planned caesarean section. There are others adverse factors that can complicate childbirth: a large or overdue fetus. In these cases, it is often chosen. In some cases, the need to end the birth through surgery caesarean section appears only in their course.

The regular set of all movements that the fetus makes while passing through the mother's birth canal is calledbiomechanism of childbirth . Against the background of translational movement along the birth canal, the fetus performs flexion, rotational and extensor movements.

Occipital presentation such a presentation is called when the fetal head is in a bent state and its lowest located area is the back of the head. Occiput births account for about 96% of all births. With occipital presentation, there may be front and rear view. front view more often observed in the first position, rear - in the second.

The entry of the head into the entrance of the pelvis is made in such a way that the sagittal suture is located along the midline (along the axis of the pelvis) - at the same distance from the pubic joint and the promontory - synclitic(axial) insertion. In most cases, the fetal head begins to insert into the entrance in a state of moderate posterior asynclitism. In the future, during the physiological course of childbirth, when contractions intensify, the direction of pressure on the fetus changes and, in connection with this, asynclitism is eliminated.

After the head has descended to the narrow part of the pelvic cavity, the obstacle encountered here causes an increase in labor activity, and at the same time strengthening and various movements fetus.

BIOMECHANISM OF DELIVERY IN ANTERIOR VIEW OF OCCIPULAR PRESENTATION

First moment - flexion of the head.

It is expressed in the fact that the cervical part of the spine bends, the chin approaches the chest, the back of the head drops down, and the forehead lingers over the entrance to the small pelvis. As the back of the head lowers, the small fontanel is set below the large one, so that the leading point (the lowest point on the head, which is located on the wire midline of the pelvis) becomes a point on the sagittal suture closer to small relative. In the anterior view of the occipital presentation, the head is bent to a small oblique size and passes through it into the entrance to the small pelvis and into the wide part of the small pelvic cavity. Consequently, the fetal head is inserted into the entrance to the small pelvis in a state of moderate flexion, synclitically, in transverse or in one of its oblique dimensions.

second moment - internal rotation of the head (correct).

The fetal head, continuing its translational movement in the pelvic cavity, encounters resistance to further advancement, which is largely due to the shape of the birth canal, and begins to rotate around its longitudinal axis. The rotation of the head begins when it passes from the wide to the narrow part of the pelvic cavity. At the same time, the back of the head, sliding along the side wall of the pelvis, approaches the pubic articulation, while the anterior section of the head departs to the sacrum. The sagittal suture from the transverse or one of the oblique dimensions subsequently passes into the direct size of the exit from the small pelvis, and the suboccipital fossa is established under the pubic joint.

Third moment - extension of the head.

The fetal head continues to move through the birth canal and at the same time begins to unbend. Extension during physiological childbirth occurs at the exit of the pelvis. The direction of the fascio-muscular part of the birth canal contributes to the deviation of the fetal head towards the womb. The suboccipital fossa abuts against the lower edge of the pubic articulation, a point of fixation, support is formed. The head rotates with its transverse axis around the fulcrum - the lower edge of the pubic articulation - and within a few attempts it is completely unbent. The birth of the head through the vulvar ring occurs with a small oblique size (9.5 cm). The back of the head, crown of the head, forehead, face and chin are born in succession.

Fourth moment - internal rotation of the shoulders and external rotation of the fetal head.

During the extension of the head, the fetal shoulders have already inserted into the transverse dimension of the entrance to the small pelvis or into one of its oblique dimensions. As the head follows the soft tissues of the pelvic outlet, the shoulders move in a helical fashion along the birth canal, that is, they move down and at the same time rotate. At the same time, with their transverse size (distantia biacromialis), they pass from the transverse size of the small pelvic cavity into an oblique one, and in the plane of the exit of the small pelvic cavity into a straight size. This rotation occurs when the fetal body passes through the plane of the narrow part of the pelvic cavity and is transmitted to the born head. In this case, the nape of the fetus turns to the left (in the first position) or right (in the second position) thigh of the mother. The anterior shoulder now enters under the pubic arch. Between the anterior shoulder at the place of attachment of the deltoid muscle and the lower edge of the symphysis, a second point of fixation, support is formed. Under the influence of birth forces, the fetal body flexes in the thoracic spine and the birth of the fetal shoulder girdle. The anterior shoulder is born first, while the posterior one is somewhat delayed by the coccyx, but soon bends it, protrudes the perineum and is born above the posterior commissure during lateral flexion of the body.

After the birth of the shoulders, the rest of the body, due to the good preparedness of the birth canal by the born head, is easily released. The head of the fetus born in the anterior occipital presentation has a dolichocephalic shape due to the configuration and the birth tumor.

BIOMECHANISM OF DELIVERY IN POSTER VIEW OF OCCIPULAR PRESENTATION

With occipital presentation, regardless of whether the occiput at the beginning of labor is turned anteriorly, to the womb or backwards, to the sacrum, by the end of the period of exile, it is usually set under the pubic joint and the fetus is born in 96% in the anterior view. And only in 1% of all occipital presentations the child is born in the rear view.

Occipital posterior birth is a variant of the biomechanism in which the birth of the fetal head occurs when the back of the head is facing the sacrum. The reasons for the formation of the rear view of the occiput presentation of the fetus may be changes in the shape and capacity of the small pelvis, functional inferiority of the muscles of the uterus, features of the shape of the fetal head, premature or dead fetus.

On vaginal examination determine a small fontanel at the sacrum, and a large fontanelle at the bosom. The biomechanism of childbirth in the posterior view consists of five moments.

First moment - flexion of the fetal head.

In the posterior view of the occiput presentation, the sagittal suture is set synclitically in one of the oblique dimensions of the pelvis, in the left (first position) or in the right (second position), and the small fontanelle is turned to the left and posteriorly, to the sacrum (first position) or to the right and posteriorly, to sacrum (second position). The bending of the head occurs in such a way that it passes through the plane of entry and a wide part of the pelvic cavity with its average oblique size (10.5 cm). The leading point is the point on the swept seam, located closer to the large fontanel.

second moment - internal wrong head rotation.

Swept seam from oblique or transverse dimensions makes a 45° or 90° turn , so that the small fontanel is behind the sacrum, and the large one is in front of the bosom. Internal rotation occurs when passing through the plane of the narrow part of the small pelvis and ends in the plane of the exit of the small pelvis, when the sagittal suture is set in a straight size.

Third moment - further ( maximum) head flexion.

Due to the fact that the biomechanism of labor in the posterior occipital presentation includes an additional and very difficult moment - the maximum flexion of the head - the period of exile is delayed. This requires additional work of the muscles of the uterus and abdominals. soft tissues pelvic floor and perineum exposed strong stretching and are often injured. Prolonged labor and increased pressure from the birth canal, which the head experiences at its maximum flexion, often lead to fetal asphyxia, mainly due to the violation cerebral circulation.

The mechanism of labor begins in that plane of the pelvis, in which the fetus encounters an obstacle as it advances.

Some advancement of the head is observed during pregnancy. With the onset of childbirth, the forward movement of the head resumes at the first contractions. normal delivery when the head moves from the wide to the narrow part of the pelvic cavity, the fetus encounters an obstacle To overcome the obstacle encountered by the head, uterine contractions alone are not enough. This requires attempts, during which, due to pressure, the fetus moves towards the exit from the birth canal, despite the fact that the mechanism of childbirth can begin in the period of disclosure, more often it occurs in the period of exile, when the head moves from the wide to the narrow part of the pelvic cavity

During the entire period of expulsion, the fetus and the birth canal continuously influence each other. At the same time, the fetus tends to stretch the birth canal, according to its shape, which tend to tightly embrace the fetus with the surrounding posterior waters and adapt to its shape. As a result of the interaction of the fetus and the birth canal, the shape of the fetal egg (fetus, posterior water, placenta) and the birth canal gradually come into full compliance with each other. The walls of the birth canal tightly cover the entire fetal egg, with the exception of the lowest segment (segment) of the head

Fig.5.12. The mechanism of childbirth in the anterior view of the occipital presentation. a - the first moment: 1 - flexion of the head, 2 - view from the side of the exit of the pelvis (sagittal suture in the transverse dimension of the pelvis); b - second moment: 1 - internal rotation of the head, 2 - view from the side of the exit of the pelvis (sagittal suture in the right oblique size of the pelvis); c - completion of the second moment: 1 - internal rotation of the head is completed, 2 - view from the side of the pelvis (the sagittal suture is in the direct size of the pelvis).

Rice. 5.12. Continuation

d - the third moment of extension of the head after the formation of the fixation point (the head with the area of the suboccipital fossa came under the pubic arch), e - the fourth moment of the external rotation of the head, the birth of the shoulders (the anterior shoulder is delayed under the symphysis), e - the birth of the shoulders, the rear shoulder rolls out above the perineum

As a result, favorable conditions to expel the fetus from the birth canal.

In the anterior view of the occipital presentation, four main points of the mechanism of childbirth are distinguished (Fig. 5 12, a-g)

First moment- flexion of the head (flexio capitis). Under the influence of intrauterine and intra-abdominal pressure the cervical part of the spine bends, the chin approaches the chest, the back of the head drops down. As the back of the head lowers, the small fontanel is set below the large one, gradually approaches the median (wire) line of the pelvis and finally becomes the lowest part of the head - the wire point.

Flexion of the head allows it to pass through the cavity of the small pelvis in the smallest or close to it size - small oblique (9.5 cm). However

At normal ratio sizes of the pelvis and head, there is no need for maximum flexion of the head: the head bends as much as necessary to pass from the wide to the narrow part of the pelvic cavity.

second moment- internal rotation of the head (rotatio capitis interna). The fetal head, during its translational movement in the pelvic cavity, when it passes from the wide to the narrow part, encountering an obstacle to further advancement, simultaneously with bending, begins to rotate around its longitudinal axis. At the same time, the back of the head, sliding along the side wall of the pelvis, approaches the pubic joint, while the anterior section of the head departs to the sacrum. This movement is easy to detect by observing the change in the position of the swept seam (see Fig. 4.15, A1, B1, C1). The sagittal suture, located before the described rotation in the cavity of the small pelvis in the transverse or one of the oblique dimensions, subsequently passes into the direct dimension. The rotation of the head ends when the sagittal suture is set in the direct size of the exit, and the suboccipital fossa is set under the pubic joint.

This rotation of the head is preparatory to the third moment of the birth mechanism, which without it would have taken place with great difficulty or not at all.

Third moment- extension of the head (deflexio capitis). The fetal head continues to move through the birth canal and at the same time begins to unbend. Extension during the physiological course of childbirth occurs at the outlet of the pelvis. Extension begins after the suboccipital fossa rests against the lower edge of the pubic joint, forming a fixation point (hypomochlion). The head rotates with its transverse axis around the fixation point (the lower edge of the pubic symphysis) and in a few attempts it fully unbends and is born. At the same time, the parietal region, forehead, face and chin sequentially appear from the genital slit. The birth of the head through the vulvar ring occurs with its small oblique size.

Fourth moment- internal rotation of the body and external rotation of the head (rotatio trunci interna seu rotatio capitis externa). During the extension of the head, the fetal shoulders are inserted into the transverse dimension of the entrance or into one of its oblique dimensions as the head advances. In the exit plane of the pelvis, following it, the shoulders of the fetus spirally move along the pelvic canal. With their transverse size, they pass from the transverse to the oblique, and when they exit, into the direct size of the pelvis. This rotation is transmitted to the born head, while the nape of the fetus turns to the left (in the first position) or right (in the second position) thigh of the mother. The front shoulder turns to the pubic joint, the back - to the sacrum. Then the shoulder girdle is born in the following sequence: first, the upper third of the shoulder, facing anteriorly, and then, due to lateral flexion of the spine, the shoulder, facing backwards. Next, the entire body of the fetus is born.

All of the listed moments of the mechanism of childbirth are performed with the translational movement of the fetal head, and there is no strict distinction between them (Fig. 5.13).

The first moment of the mechanism of childbirth is not limited to head flexion alone. It is also accompanied by translational movement, its advancement along the birth canal, and later, when flexion ends, and the beginning of the internal rotation of the head. Consequently,

The second moment of the mechanism of childbirth is a combination of translational and rotational movements. Along with this, at the beginning of the internal rotation, the head finishes bending, by the end of the rotation it begins to unbend Of all these movements, the rotation of the head is the most pronounced, therefore the second moment of the mechanism of childbirth is called "internal rotation of the head"

The third moment of the mechanism of childbirth is made up of translational movement and extension of the head. However, along with this, the head continues to make an internal rotation almost until birth. At this moment of the mechanism of childbirth, the extension of the head is the most pronounced, as a result of which it is called "extension of the head"

The fourth moment of the mechanism of childbirth is composed of the translational movement of the head and the internal rotation of the shoulders, as well as the external rotation of the head associated with this. The movement that determines this moment is the most easily detected external rotation of the head. Simultaneously with the movements of the fetal head listed above, and sometimes preceding them, movements of the entire his torso

The mechanism of labor in primiparous is essentially the same as in multiparous. In multiparous, it usually does not begin during the period of disclosure, as it often happens in primiparas, but later in the period of exile, after the outflow of amniotic fluid. The movement of the head through the birth canal may begin during the period opening in those of the multiparous women who, despite postponed childbirth, well preserved functional state muscles of the uterus and abdominals, diaphragm, abdominal wall, pelvic floor

Each of the above rotations of the head can be easily detected during a vaginal examination of a woman in labor by displacement of the swept suture from one size of the pelvic cavity to another, by the relative position of the large and small fontanelles. Quite valuable data can also be obtained by the method of external examination Systematically and carefully performed palpation of parts of the fetus (back, occiput, forehead, chin, anterior shoulder) and cardiac monitoring of heart tones allow to determine the change in their relative position in relation to each other and to the birth canal

By American classification seven main fetal movements during childbirth are distinguished: 1) insertion of the head, 2) advancement of the head, 3) flexion of the head, 4) internal rotation of the head, 5) extension of the head, 6) external rotation of the head and internal rotation of the body, 7) expulsion of the fetus.

5.4.2. The mechanism of labor in the posterior occipital presentation

With occipital presentation, regardless of the type at the beginning of labor, by the end of the period of expulsion, the occiput is usually set under the pubic joint, and the fetus is born in the anterior view (Fig. 5.14).

With the initially rear view of the first position during the internal rotation, the swept seam rotates counterclockwise and successively passes from the left oblique to the transverse, then to the right oblique and, finally, to the direct size. In the second position, which is much more common, in the rear view during the internal rotation of the head, the swept seam rotates clockwise. At the same time, it goes from the right oblique first to the transverse, then to the left oblique and, finally, to the direct size of the exit. In this regard, the small fontanelle in the posterior view of the occiput presentation describes a large arc - about 135 ° and the initial posterior view, both in the first and in the second position, subsequently turns into an anterior view.

However, this does not always happen. In some cases (in 1% of all occiput presentations), the fetus is born in a posterior occipital presentation. Childbirth in the back view of the occipital presentation is a variant of the norm.

The mechanism of childbirth in the posterior view of the occipital presentation consists of the following points.

First moment- flexion of the head in the plane of the entrance to the small pelvis. The wire point is a small fontanelle. The head is inserted into the entrance to the pelvis more often in the right oblique size, less often in the left.

second moment consists in the internal rotation of the head, in which the swept seam, when it passes into the narrow part of the plane of the small pelvis, is located in a direct size. The occiput is turned backwards. Often, at the same time, the wire point changes, it becomes the area between the small and large fontanel.

Third moment- maximum flexion of the head - occurs in the plane of the exit of the pelvis. This creates two fixation points. The first is the front edge of a large fontanel, which approaches the lower edge of the womb. Due to strong flexion, the back of the head is born and a second fixation point is formed - the suboccipital fossa, which abuts against the coccyx area, and extension occurs.

Due to the fact that the head in the plane of the small pelvis is somewhat unbent, eruption occurs with an average head size, a circumference of 33 cm.

The wire point in the posterior view of the occipital presentation at the entrance to the small pelvis is the small fontanelle. In the pelvic cavity, the area between the small and large fontanel becomes a conducting point.

The configuration of the head in the posterior view of the occipital presentation is pre-lychocephalic. The birth tumor is located on the presenting parietal bone closer to the large fontanel.

Rice. 5.14. The mechanism of labor in the posterior view of the occiput presentation a - the first moment of flexion of the head, b - the second moment of internal rotation of the head, c - the third moment of additional flexion of the head

When conducting labor, there are difficulties in determining the location of the head in relation to the planes of the pelvis. Often, if the head is located in a small segment at the entrance to the pelvis, it seems that it is already in the cavity of the small pelvis. Only with a vaginal examination is it possible to determine exactly in which plane of the pelvis the head is located.

Taking into account the fact that the mechanism of childbirth in the posterior view includes an additional and very difficult moment - the maximum flexion of the head, the period of exile is delayed. Childbirth in the posterior view of the occipital presentation differs in duration, is accompanied by an excessively large expenditure of tribal forces. The pelvic floor and perineum are subject to great strain and are often torn. Prolonged labor and increased pressure from the birth canal, which the head experiences at its maximum flexion, often lead to fetal hypoxia, impaired cerebral circulation, and cerebral lesions.

The reasons for the formation of the rear view can be due to both the fetus (small head, in some cases difficult flexion of the cervical spine, etc.), and the state of the birth canal of the woman in labor (anomalies in the shape of the pelvis and pelvic floor muscles).

5.4.3. The influence of the mechanism of childbirth on the shape of the head

In the process of passing the head through the birth canal, it adapts to the shape and size of the birth canal (mother's pelvis). The adaptability of the head is limited by known limits and depends on the displacement of the bones of the skull in the region of the sutures and fontanelles, as well as on the ability of the bones of the skull to change shape (flatten, bend) when passing through the small pelvis.

Changing the head when it passes through the birth canal is called head configuration. The configuration depends on the characteristics of the head and the birth canal. The wider the seams softer than the bone, the greater the ability of the head to configure. In addition, the configuration is significant when there is difficulty in advancing the head (narrowing of the pelvis). The shape of the head changes depending on the mechanism of childbirth. In cases of occiput presentation (especially posterior view), the head is pulled towards the back of the head, taking on a dolichocephalic shape (Fig. 5.15). If the birth is normal, then the configuration of the head is weakly expressed and does not affect the health and development of the newborn: changes in the shape of the head disappear without a trace soon after delivery.

In childbirth during the period of exile, in addition to changing the shape of the head, a birth tumor may appear (Fig. 5.16). It represents tissue edema in the lowest anterior section (leading point) of the presenting part. Tissue edema occurs due to obstruction of outflow venous blood from that part of the presenting part, which is located below the contact zone.

A generic tumor develops with head presentations and is formed after the outflow of water only in live fetuses. With occiput presentation, the birth tumor is located closer to the back of the head in the region of the right or left parietal bone, depending on the position. At first position most of the tumor is located on the right parietal bone, with the second - on the left.

According to the configuration of the head of the born fetus and the location on it

Rice. 5.15. Moderate head configuration in occipital presentation.

Rice. 5.16. Birth tumor on the head of a newborn.

1 - skin; 2 - bone; 3 - periosteum; 4 - swelling of the fiber (birth tumor).

birth tumor can be judged on the mechanism of childbirth, the nature of the insertion of the head (synclitic or asynclitic), the degree of its flexion, etc. If the mechanism of labor deviates from the typical variant, the configuration of the head and the location of the birth tumor change.

The birth tumor does not have sharp contours; it passes through fontanelles and sutures. The longer the birth after the outflow of amniotic fluid, the more pronounced the birth tumor. In some cases, it can be mistaken (during vaginal examination) for amniotic sac. A reliable differential diagnostic sign is the presence of hair and swelling, determined by touch with a birth tumor. In the case of normal childbirth, the birth tumor does not reach a large size and disappears a few days after childbirth.

With difficult passage of the head through the birth canal and operative delivery, a blood tumor or cephalohematoma may occur on the head (Fig. 5.17, a, b) - hemorrhage under the periosteum.

5.4.4. Theories of the mechanism of childbirth

There are numerous theories in the literature explaining the flexion and rotation of the fetus during childbirth, which are of historical interest only. It is currently believed that in the mechanism of childbirth great importance have both physical (spatial relationships of the fetus and the birth canal) and biological (the strength of intrauterine pressure and muscle resistance of individual parts of the fetus) factors. A significant role in the mechanism of childbirth belongs to the muscles of the pelvic floor. As a result of the interaction of all these factors, individual

Rice. 5.17. Cephalhematoma of the newborn

a - scheme: 1 - skin, 2 - bone, 3 - periosteum, 4

hematoma, b - general form

The mechanism of labor can be explained as follows. The glans, slightly bent before the second stage of labor, flexes under the influence of expelling forces, taking into account the rule of uneven leverage. The manifestation of this law is possible because the junction of the spine with the base of the skull is not in the center of the skull, but eccentrically - closer to the back of the head than to the chin. In this regard, most of the expelling forces are concentrated on the short arm of the lever, i.e. on the back of the head. At the same time, the long arm of the lever, at the end of which is the face of the fetus with its largest convex and voluminous part - the forehead, meets resistance from the innominate line of the pelvis. This creates two opposing forces. One of them presses occipital part heads from top to bottom, i.e. towards the exit of the pelvis, and forces it to move forward, the other, counteracting this pressure, delays the front of the head (forehead) and does not allow it to follow the back of the head. As a result, the back of the head falls lower than the forehead, the head is bent and at the same time its deeper penetration into the pelvic cavity.

The following factors contribute to the internal rotation of the head: adaptation of the head and its passage along the most large sizes planes of the pelvis, the structure of the pelvic floor and the contraction of its muscles. With translational movement, the head, tightly covered by the walls of the small pelvis, slides along their surfaces, which are a system of inclined planes. Under such conditions, the head follows the dimensions of the pelvis, of which the largest at the entrance to the pelvis is transverse, in the plane of the pelvis - oblique and at the exit from the pelvis - straight. Moving along the walls of the pelvis that are tightly adjacent to it and at the same time being under the influence of the muscles of the pelvic floor, the head makes an internal turn, adapting its size to the large size of the pelvis.

To turn the head with the back of the head anteriorly, the following factors are also important: 1) the structure of the pelvis, since its front wall is shorter than the back

(sacrum), it provides the least resistance to the advancing head; 2) the muscles of the pelvic floor, especially the levators, which, by contracting, contribute to the rotation of the occiput anteriorly, and then the extension of the head.

To advance the head, the shape of the head and pelvis matters. The head as an object of childbirth is a kidney-shaped body with two poles - the back of the head and the chin. Both of these poles are connected by a "line of head curvature", which is turned by the bulge of a large fontanelle. The birth canal also has the form of an arc, the convex side of which is turned backwards. The head easily passes through the pelvis if the head and pelvic curvature match. In the process of adapting the head curvature to the pelvic one, an internal rotation occurs.

The internal rotation of the body and the external rotation of the head are mainly determined by the rotation of the shoulder girdle. The shoulder girdle, passing sequentially through the plane of entry into the pelvis (in a transverse section), the pelvic cavity - in an oblique size and the exit plane (in a direct size), performs a rotational movement, which is transmitted to the born head.

MECHANISM OF DELIVERY IN ANTERIOR VIEW OF OCCIPULAR PRESENTATION.

Determine which formation belongs to the anterior, posterior, lower horns, central part

Praesentatio occipitalis visus anterior.

(First option)

Occipital presentation such a presentation is called when the fetal head is in a bent state and its lowest located area is the back of the head. Occiput births account for about 96% of all births.

The anterior view of the occipital presentation refers to the physiological type of the biomechanism of childbirth (the natural articulation of the fetus is preserved). Biomechanism of childbirth - this is a natural set of all movements that the fetus makes, passing through the mother's birth canal. Against the background of translational movement along the birth canal, the fetus performs flexion, rotational and extensor movements.

The biomechanism of childbirth consists of four moments.

1 moment – flexiocapitis- flexion of the head. In this case, the head is installed with a swept seam in the transverse, less often in one of the oblique dimensions of the plane of the entrance of the small pelvis. The sagittal suture is located at the same distance from the pubic joint and the cape - synclitic(axial) insertion Leading (wired) point- small spring (fontanella minor).

Rice. 2. The second moment of the biomechanism of childbirth. A - internal rotation of the head, B - view from the side of the exit plane of the small pelvis; sagittal suture in the right oblique size of the pelvis (from: V.I. Bodyazhina et al. "Obstetrics" M .: Litera, 1995).

Rice. 3. The second moment of the biomechanism of childbirth. A - internal rotation of the head is completed, B - view from the side of the exit plane of the small pelvis; sagittal suture in the direct size of the pelvis (from: V.I. Bodyazhina et al. "Obstetrics" M .: Litera, 1995).

3 moment – deflexio (extensio) capitis- extension of the head. Extension of the head occurs around the point of fixation ( puntum fixum seu hypomochlion), which is suboccipital fossa. As a result of extension of the head, its birth occurs. The back of the head is born first, then the parietal tubercles, after that front part skulls. Cutting diameter - small oblique size - diameter suboccipitobregmatica- 9.5 cm, circumferentia suboccipitobregmatica- 32 cm.

Rice. 4. The third moment of the biomechanism of childbirth. A - the beginning of extension, B - extension of the head (from: V.I. Bodyazhina et al. "Obstetrics" M .: Litera, 1995).

4 moment – rotatio trunci interna et capitis externa- internal rotation of the body and external rotation of the head with the face to the mother's thigh, opposite to the position of the fetus. The posterior shoulder is placed in the sacral cavity, and the anterior shoulder is cut through to the upper third (to the point of attachment of the deltoid muscle to humerus) and rests against the lower edge of the symphysis; a fixation point is formed, around which the fetal body is bent into cervicothoracic region in accordance with the direction of deepening of the birth canal. In this case, the back shoulder is born above the perineum, and then the front shoulder is completely released.

Rice. 6. Dolichocephalic