Occipital presentation of the fetus: the mechanism of childbirth. Anterior occipital presentation

Performs translational and rotational movements. The totality of all movements of the fetus when passing through the birth canal is called the mechanism of childbirth. The movement of the fetus (head) begins simultaneously with the appearance of a regular labor activity. To the moment full disclosure of the uterine os, the head is already in the pelvic cavity, completing the internal rotation (Fig. 13).

During the period of disclosure, with the normal mechanism of childbirth, the fetal head enters the small one in such a way that its sagittal suture is at the same distance from the pubic articulation and the sacral cape of the promontorium - a synclitic insertion. However, sometimes even with a normal mechanism of labor (in primiparous with elastic abdominal walls, in multiparous with flaccid walls), the sagittal suture is closer to the promontorium. This off-axis asynclitic insertion is usually transient and disappears soon. On the contrary, strong degrees of asynclitic insertion, especially posterior asynclitism (sagittal suture closer to the symphysis), are observed with (see).

In the anterior view of the occipital presentation, the head, when passing through the birth canal, makes successively certain movements (Fig. 14).

Mechanism and management of childbirth occipital presentation: rice. 13-head at the bottom of the pelvis finishes rotation, its wire point (small fontanelle) stands anteriorly to the left; rice. 14 - movement of the head when passing through the birth canal (left occipital presentation): from top to bottom - entry of the head into the pelvis, the beginning of rotation, rotation is completed; rice. 15 - bending of the head; rice. 16 - the head has finished rotation, the swept seam is in direct size exit of the pelvis; rice. 17 - the beginning of the extension of the head, the head "cuts"; rice. 18 - the head is "cut through"; rice. 19 - external rotation of the head to the right thigh of the mother, the front shoulder is installed under the pubic joint; rice. 20 - the birth of the front shoulder; rice. 21 - the birth of the back shoulder.

1. Flexion (flexion) - rotation around the transverse (frontal) axis (Fig. 15). Due to the bending, one pole of the head (small fontanel) becomes the lowest point of the advancing head. This point is called the wire point: it first descends into the entrance of the pelvis, during the rotation it always goes ahead and at the end of the rotation it is under the pubic joint (the first one is shown in the genital gap).

2. The second rotation of the head occurs around the longitudinal axis - the internal rotation of the head with the back of the head forward (rotation). This rotation of the head is done in such a way that the back of the head turns anteriorly, and the anterior region of the large fontanelle - posteriorly. Making the second rotation, the head passes with an arrow-shaped seam from the transverse size of the pelvis to a straight line. This is important to note (for diagnostic purposes); at internal study in the direction of the swept seam, you can determine the location of the head: at the entrance to the pelvis, the swept seam is in a transverse size, slightly oblique; in the pelvic cavity - in an oblique size; at the bottom of the pelvis - in a straight line (Fig. 14 and 16).

3. The third rotational movement of the head around the frontal axis - the transition to a state of extension (deflection). Small fontanel (wire point) from the entrance to the pelvis to pelvic floor moves in a straight line, but from here and further, in order to reach the vulgar ring, it must move along the wire axis of the pelvis - along a parabola. In this case, the fetal head should move from a bent state to an unbent one (Fig. 17 and 18).

When passing through the vulva, the extension of the head reaches a maximum. Under the pubic arch, the area of ​​\u200b\u200bthe suboccipital fossa finds a fulcrum for itself, around which the head does extension; it seems to roll over, and at first the forehead cuts through, then the face and, finally, the chin. This point of support (at this case suboccipital fossa) is commonly called the pivot point (hypomochlion), or fixation point.

When the head has completely left the vulva (cut through), it makes another rotation around the longitudinal axis (by 90 °): backward, the face turned during eruption turns towards the mother's thigh, in the first position - towards the right, in the second - towards the left thigh . This will be the external rotation of the head (some consider it the fourth moment of the labor mechanism, Fig. 19).

The birth of the shoulders and torso of the fetus occurs according to the same mechanism: the shoulders enter the pelvis in a transverse or oblique size and, having reached the pelvic floor in this position, they become here in the direct size of the pelvis. After the birth of the head, the anterior shoulder is established under the pubic joint (Fig. 19 and 20), forming, as it were, a hypomochlion, around which the entire shoulder girdle is born, erupting (Fig. 21). When the shoulders are cut through, the Boulevard Ring is significantly stretched, which must be taken into account when protecting the perineum.

A. Flexion head presentation:

A) anterior occipital presentation

1. Flexion of the head (flexio capitis) - 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. Leading (wired) point - small fontanel (1)

2. Normal internal rotation of the head (rotatio capitis interna normalis) - begins at the transition from the wide part to the narrow part of the small pelvis, ends with the establishment of an sagittal suture in the direct size of the exit plane of the small pelvis. The back of the head is turned forward, the forehead is turned backward (2)

3. Extension of the head (extensio capitis) - occurs around the fixation point - the 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. The eruption diameter is a small oblique size (3).

4. Inner turn of the body and external rotation of the head (rotatio trunci interna et capitis externa) with the face towards the mother's thigh, opposite to the position of the fetus (towards the right thigh at the 1st (left) position, towards the left at the 2nd (right) position) (4).

B) rear view of the occipital presentation.

1. Flexion of the head (flexio capitis) - the head is installed with a swept seam in the transverse, less often in one of the oblique dimensions of the plane of entry into the small pelvis. The wire point is the middle of the distance between the large and small fontanelles (1).

2. Internal rotation of the head (rotatio capitis interna anormalis) - ends with the establishment of an sagittal suture in the direct size of the exit plane from the small pelvis with the back of the head facing backwards (wrong rotation) (2)

3. Additional flexion of the head (flexio capitis accessorius) - occurs around the first fixation point (the border of the scalp of the forehead). As a result of the third moment of the biomechanism of childbirth, occipital part skulls (3)

4. Extension of the head (extensio capitis) - occurs around the second fixation point - the suboccipital fossa. The eruption diameter is the average oblique size. The birth of the head occurs face anteriorly (4)

5. Internal rotation of the shoulders and external rotation of the head (rotatio trunci interna et capitis externa) - face to the mother's thigh, opposite to the position of the fetus (5)

B. Extension head presentation.

A) anterior presentation

1. Slight extension of the head - the head is installed with an arrow-shaped suture in the transverse size of the plane of entry into the small pelvis. Wire point - large fontanelle (1)

2. Internal rotation of the head - begins in the cavity of the small pelvis and ends with the establishment of an arrow-shaped seam in the direct size of the plane of the exit of the small pelvis. A feature of the internal rotation is the obligatory formation of a rear view (occiput to the sacrum) (2)

3. Bending of the head around the first point of fixation - the bridge of the nose, as a result, the region of the anterior crown is cut through (3)

4. Extension of the head around the second fixation point - the suboccipital fossa, as a result, the head is born. Eruption Diameter - Large Straight Head Size (4)

B) frontal presentation

1. Extension of the head medium degree- the frontal suture is set in the transverse size of the plane of the entrance to the small pelvis; wire point - middle of the forehead (1)

2. Internal rotation of the head - ends with the establishment of the frontal suture in the direct size of the exit plane of the small pelvis. The peculiarity of the internal rotation: a) the obligatory formation of the rear view (back of the head to the sacrum); b) internal rotation begins and ends at the pelvic floor (2)

3. Flexion of the head - occurs around the first fixation point - upper jaw, which rests on the lower edge of the symphysis. As a result, it cuts frontal part skulls (3)

4. Extension of the head around the second fixation point - the suboccipital fossa, which is fixed in the coccyx area. The eruption diameter is the average oblique head size. The head is born (4)

5. External rotation of the head and internal rotation of the shoulders (5)

B) facial presentation

1. Maximum extension of the head - wire point - chin. The longitudinal facial line is set in the transverse size of the plane of the entrance to the small pelvis (1)

2. Internal rotation of the head with the back of the head, Chin to symphysis (anterior view). Turning the head with the chin backwards makes it impossible to give birth through the natural birth canal. Internal rotation begins and ends at the pelvic floor (2)

3. Flexion of the head - fixation point - the hyoid bone is fixed to the pubic arch, and the head is born. Cutting diameter - vertical dimension heads (3)

4. External rotation of the head, internal rotation of the shoulders.

The biomechanism of childbirth in breech presentation:

1. Lowering the pelvic end: the wire point is the buttock, facing anteriorly and standing below the rear

2. Internal rotation of the buttocks: the front buttock - to the symphysis, the back - to the sacrum.

3. Insertion and eruption of the buttocks: the point of fixation - the region of the ilium of the fetus - rests against the pubic arch.

4. The birth of the shoulder girdle

5. The birth of the head - the head rests against the pubic arch with a fixation point - the suboccipital fossa.

GOU VPO CHELYABINSK STATE MEDICAL ACADEMYDEPARTMENT OF OBSTETRICS AND GYNECOLOGY № 1

BIRTH WAYS. FETUS AS AN OBJECT OF BIRTH.

BIOMECHANISM OF DELIVERY IN HEAD

FETUS PRESENTATION

Compiled by: Associate Professor of the Department of Obstetrics and Gynecology No. 1 Plekhanova L.M.

The pelvis consists of 4 bones: 2 pelvic (nameless), sacrum, coccyx.

The pelvic bone is formed as a result of the fusion of 3 bones - the pubic, ischium and ilium.

Ilium (os. Ileum) - steam room consists of a body and a wing, on which spines and a crest stand out. Connection with the sacrum - sacroiliac - semi-joint. On this bone is the border between the small and large pelvis - the nameless line.

Ichium (os. ischi) - steam room consists of a body and two branches - lower and upper. It has an ischial tuberosity and an ischial spine.

The pubic or pubic bone (os. pubis) is a steam room, consists of a body, two branches, are interconnected by means of a semi-joint - symphysis.

The sacrum (os.sacrum) is formed by 5 fused vertebrae, has a protrusion -promontorium - the border of the pelvic area.

The coccyx (os. coccyges) consists of 4-5 fused vertebrae, mobile - connected to the sacrum by sacrococcygeal articulation.

Pelvic planes

1. The plane of entry into the small pelvis.

Borders - upper edge womb, nameless lines, promontorium. Straight size - 11 cm, right and left oblique - 12 cm, transverse - 13 cm.

2. The plane of the wide part of the small pelvis

Borders - the middle of the inner surface of the symphysis, on the sides - the middle of the inner surfaces of the acetabulum, behind - the connection of II and III sacral vertebrae. Straight and transverse dimensions - 12.5 cm.

3. The plane of the narrow part of the small pelvis.

Borders - the lower edge of the symphysis, the spines of the ischial bones, the sacrococcygeal joint. Straight size - 11-11.5 cm, transverse - 10.5 cm.

4. Plane of exit from the small pelvis

Borders - the lower edge of the symphysis, ischial tuberosities, the tip of the coccyx. Straight size - 9.5-11 cm, transverse - 11 cm.

The wire axis of the pelvis is a line passing through the geometric centers of all planes, along which the fetus moves.

The angle of inclination of the pelvis is the ratio of the plane of entry into the small pelvis to the horizontal plane (norm 55-68) - the measurement is carried out by a goniometer.

Rhombus of Michaelis - a platform on the back of the sacrum. Borders: superior recess between the spinous process of the 5th lumbar vertebra and the beginning of the sacral crest, inferior - the apex of the sacrum, lateral - posterior spines ilium. Muscular fences: upper half - protrusions of large spinal muscles, below - protrusions of the gluteus maximus muscles. The shape normally approaches a square, with anomalies of the pelvis and spine, its shape changes. Its longitudinal and transverse diagonals are normally 11 cm each.

The difference between the female pelvis and the male pelvis: the pelvis is more capacious, the wings of the ilium are deployed, the shape of the entry plane is oval, the bone formations of the small pelvis are thinner and smoother, the birth canal is cylindrical, the narrower width of the pubic articulation and the obtuse pubic angle.

Determining the size of the pelvis: 1 D. spinarum - the distance between the anterior-superior awns - 25-26 cm. 2. D. cristarum - the distance between the most distant points of the iliac crests - 28-29 cm.

    D. trochanterica - distance between greater skewers thigh bones- 30-31 cm.

    C. externa - external conjugate, 20 cm, subtract 9 cm to calculate the true one.

    C. diagonalis - 12.5-13 cm, to calculate the true subtract 1.5-2 cm.

    The direct size of the exit plane, after measuring with a tazometer, subtract 1.5 cm.

    The transverse dimension of the exit plane is measured with a centimeter tape, 1.5 cm is added to the obtained value.

    Soloviev index - circle wrist joint reflects to some extent anatomical features bones (their massiveness) is normally 14-15 cm.

Anatomy of the pelvic floor muscles

The pelvic floor is formed by three soy muscles separated by formations: 1. The lower (outer) layer of muscles consists of four muscles, in shape this layer resembles the number 8, in addition to them there is a steam room

    The middle layer consists of a muscular-fascial plate - the urogenital diaphragm.

    The top layer of muscles is m.levatoris or the so-called pelvic diaphragm.

Function of the pelvic floor: support for the internal genital organs and participation in the formation of the birth canal.

FETUS AS AN OBJECT OF BIRTH

Signs of fetal maturity: height from 48 cm, weight over 2500.0 g, convex rib cage, the umbilical ring in the middle of the distance between the womb and the navel, the subcutaneous fat layer is developed, the remains of a cheese-like lubricant. Nails at the fingertips, ear and nasal cartilages are elastic, the ovaries in boys are lowered into the scrotum, in girls the genital slit is covered with large labia, the hair is more than 2 cm long, the movements are sometimes active, the cry is loud.

The head of a mature fetus has a number of features: the bones of the skull are connected by sutures and fontanelles, the bones are elastic, the bones can move one relative to the other - these properties ensure the movement of the fetus through the birth canal with known spatial difficulties in the small pelvis. The following sutures and fontanelles are of practical importance:

    Frontal suture - separates the frontal bones

    Sagittal suture - separates the parietal bones

    Coronal suture - separates the frontal bone from the parietal on each side

    Lambdoid suture - passes between both parietal bones on one side and the occipital bone on the other.

    Large fontanel - has the shape of a rhombus and lies between four bones, two frontal and two parietal.

    Small fontanel - is a small depression in which three seams converge: swept and two lambdoid.

The most important dimensions of the fetal head are:

    Large oblique - from the chin to the most distant point on the back of the head - 13.5 cm, the circumference, respectively, of this size is 40 cm.

    Small oblique - from the suboccipital fossa to the anterior corner of the large fontanel - 9.5 cm, circumference - 32 cm.

    Medium oblique - from the suboccipital fossa to the border of the scalp (forehead) 9.5 - 10.5 cm, circumference - 33 cm.

    Direct size - from the bridge of the nose to the occiput - 12 cm, circumference - 34 cm.

    Vertical size - from the top of the crown to the sublingual region - 9.5 cm, circumference 33 cm.

    Large transverse size - the largest distance between the parietal tubercles is 9.25 cm.

    Small transverse dimension - the distance between the most distant points of the coronal suture - 8 cm.

Shoulder and pelvic girdle of the fetus. Shoulder width 12.5 cm, circumference 35 cm, hip width (between skewers) 9.5 cm, circumference 27-28 cm.

Obstetric terminology:

    The position of the fetus - the ratio of the prodoal axis of the uterus to the uterus

    The position of the fetus is the ratio of the back of the lod to the right or left side of the mother's body.

    Type of position - the ratio of the back of the fetus to the front or back wall uterus.

    Presentation - the ratio of a large part of the fetus to the entrance to the small pelvis.

    The articulation of the fetus is the mutual position of the various parts of the fetus in relation to its body and to each other.

BIOMECHANISM OF DELIVERY IN ANTERIOR VIEW OF OCCIPULAR PRESENTATION

Starting position: the head of the fetus is pressed or with a small segment at the entrance to the small pelvis, in a state of slight fixation. All moments of the biomechanism go against the background of forward movement.

    Flexion of the head - as a result, the area of ​​​​the small fontanel becomes a wire point.

    Internal rotation of the head with the back of the head anteriorly, as a result, in the exit plane, the head is set in a direct size, approaching the suboccipital fossa under

    Extension of the head - occurs around the point of fixation, as a result, the fetal head is born.

    External rotation of the head, internal rotation of the shoulders by 90, as a result, the shoulders are located in the direct size of the exit and then are born. The rotation is always towards the thigh opposite the fetal position.

BIOMECHANISM OF DELIVERY IN POSTER VIEW OF OCCIPULAR PRESENTATION

The initial position of the fetal head, as in the anterior view.

    Flexion of the head, the middle point between small and large fontanelles (crown) becomes a wire point

    Incorrect rotation (small fontanel backwards)

    Additional bending of the head - fixation points - the lower edge of the womb and the area of ​​​​the border of the hairline of the forehead.

    Extension of the head, fixation points of the coccyx region and suboccipital fossa.

    External rotation of the head, internal rotation of the shoulders. The head goes through the birth canal and is born in an average oblique size.

EXTENSION PRESENTATION OF THE FETUS

The extensor presentations include the anterior head, frontal and facial. They differ in the degree of extension of the head. With an anterior presentation, the degree of extension is the smallest, with a facial presentation - the maximum. The frequency of extensor presentation reaches 0.5-1% of all births.

Recognition of extensor presentation is based on data from external and vaginal examination. An external examination is not informative enough and does not provide accurate data in case of frontal and frontal presentations. With facial presentation, it is possible to palpate the angle between the back of the fetus and the head, pressed against the entrance to the small pelvis. The final diagnosis is made after a vaginal examination. With an anterior presentation, the large and small fontanelles are simultaneously determined, which are located on the same level or the large fontanel is lower. In the II period of childbirth, a large fontanel becomes a conducting point. With frontal presentation, the forehead, the front edge of the large fontanel, the superciliary arches, and the bridge of the nose are determined. With facial presentation, the chin, mouth and nose of the fetus are palpated.

Features of childbirth with anterior head presentation

With this type of presentation, the head passes through the small pelvis in a state of slight extension, as a result of which it goes with its straight size. The wire point is the large fontanel, and the fixation point is the epipalis and occiput. This is a fundamental difference from the posterior view of the occipital presentation, in which the head passes in an average oblique size, the wire point is the middle between the small and large fontanel, and the fixation points are the anterior edge of the scalp and the suboccipital fossa. Childbirth mechanism:

    slight extension of the head

    Internal rotation of the head (back of the head - backwards)

    Flexion with a fixation point at the nape

    Extension - with a fixation point at the occiput

    External rotation of the head and internal rotation of the shoulders

Since the direct size of the fetal head (12 cm) significantly exceeds the small oblique (9.5 cm) and medium oblique (10 cm) sizes, the second stage of labor with anterior head presentation proceeds with great difficulty. The number of complications in childbirth is increasing, which include:

    clinically narrow pelvis

    weakness of labor

    endometritis in childbirth

    ruptures of the cervix, vagina, perineum

    fetal hypoxia

In connection with these complications, the frequency of surgical delivery increases significantly.

Frontal presentation is the most unfavorable for the mother and fetus. In this presentation, the head is inserted into the small pelvis with its large size, the forehead is the wire point. Since the value of the large oblique size (13-13.5 cm) significantly exceeds normal sizes small pelvis, the latter usually appears to be an insurmountable obstacle to the passage of the head. Therefore, childbirth in the frontal presentation with a full-term fetus is usually impossible. Left to their natural course, they usually end with the appearance of a clinically narrow

pelvis and further uterine rupture or weakness of labor with

endometritis and sepsis.

Facial presentation is the most common variant of the extensor presentation. At

in it, the head is inserted into the small pelvis with its vertical (10 cm) size, and the wired

the point is the chin.

Considering that the vertical size of the head is only slightly larger than the small

oblique, the head with facial presentation has the ability to pass the small pelvis in case

his head will turn to the sacrum. When the back of the head is turned towards the bosom, childbirth is impossible.

Features of the mechanism of childbirth with facial presentation:

    maximum extension of the head, at which the front line stands in the transverse size of the entrance to the small pelvis (I moment of childbirth).

    descending into the cavity of the small pelvis, the head does not make an internal turn to the bottom of the pelvis.

    the rotation of the chin anteriorly occurs at the bottom of the pelvis (P moment).

    after the eruption of the chin, the head is fixed by the hyoid bone above the womb, after which it is bent, in which the forehead, crown and back of the head are cut through over the perineum (III moment).

    internal rotation of the shoulders and external rotation of the head occurs as in occipital presentation (IY moment).

Despite the fact that facial presentation is favorable for the outcome of childbirth, it

accompanied by a number of features: more often there is a premature outflow

amniotic fluid, the duration of labor increases (especially P railing),

increased maternal and fetal trauma.

Childbirth in a facial presentation with the back of the head facing anteriorly leads to the occurrence

clinically narrow pelvis and all subsequent complications.

Anomalies in the position and presentation of the fetus have an adverse effect on its

condition. Perinatal mortality in this pathology is much higher than in

occiput delivery, as well as the incidence of fetal hypoxia and asphyxia

newborn and various birth trauma newborns. The reasons for this are:

    The frequent occurrence of a clinically narrow pelvis and anomalies of labor activity leading to prolonged labor.

    High frequency of premature rupture of water, endometritis in labor and preterm birth.

    Prolapse of the umbilical cord in the transverse position of the fetus

    Obstetric surgery to correct the position of the fetus

The extensor presentation, in addition, causes a significant configuration of the head. In anterocephalic presentation, the head is extended towards the large fontanel (brachycephalic or "tower"). With frontal presentation, a significant deformation of the head occurs due to the protrusion of the forehead. In face presentation, the configuration of the head is dolichocephalic. The birth tumor is located on the face. Due to the swelling of the lips, the newborn cannot breastfeed on the first day, so breastfeeding is prescribed after the swelling disappears.

Children born in extensor presentations need careful monitoring by a pediatrician and, if necessary, a pediatric psychoneurologist.

A similar variant of the biomechanism is observed in almost 95% of cases of childbirth. It consists of 7 moments or stages

1st moment - insertion of the fetal head into the entrance to the small pelvis (insertio capitis). The insertion of the fetal head into the entrance to the pelvis is facilitated, first of all, by the lower segment of the uterus tapering downwards, normal condition muscle tone of the uterus and anterior abdominal wall. In addition, the muscle tone and gravity of the fetus itself, a certain ratio of the size of the fetal head and the size of the plane of entry into the small pelvis, the corresponding amount of amniotic fluid, correct location placenta.

In primiparous primiparous women, by the beginning of labor, the fetal head may be fixed at the entrance to the pelvis in a state of moderate flexion. When the fetal head comes into contact with the plane of the entrance to the pelvis, the sagittal suture is installed in one of the oblique or transverse dimensions of the plane of the entrance to the pelvis, which is facilitated by the shape of the head in the form of an oval, tapering towards the forehead and expanding towards the back of the head. The posterior fontanel faces anteriorly. In cases where the sagittal suture is located along the midline (at the same distance from the pubic symphysis and the promontory), they speak of a synclic insertion of the head. At the time of insertion, the axis of the fetus often does not coincide with the axis of the pelvis (asynclitism).

There are three degrees of asynclitism

  • 1) I degree - the swept seam is deviated by 1.5--2.0 cm anteriorly or posteriorly from the midline of the plane of the entrance to the small pelvis.
  • 2) II degree - approaches (tightly adjoins) to the pubic joint or to the cape (but does not reach them).
  • 3) III degree - the swept seam extends beyond the upper edge of the symphysis or beyond the cape. vaginal examination you can feel the fetal ear.

II and III degree asynclitism are pathological.

  • 2nd moment - flexion of the head (flexio capitis). Bending of the fetal head, fixed at the entrance to the pelvis, occurs under the action of expelling forces according to the law of a lever having two unequal arms. Expelling forces through the spine act on the fetal head, which is in close contact with the symphysis and cape. The place of application of force on the head is located eccentrically: the atlantooccipital joint is located closer to the back of the head. Because of this, the head is an unequal lever, the short arm of which is turned towards the back of the head, and the long one towards the forehead. As a result, there is a difference in the moment of forces acting on the short (the moment of force is less) and the long (the moment of force is greater) arms of the lever. The short arm goes down and the long one goes up. The back of the head falls into the small pelvis, the chin is pressed to the chest. By the end of the flexion process, the head is firmly fixed at the entrance to the pelvis, and the posterior (small) fontanel is located below the nameless line. It becomes the leading point. The back of the head, as the head descends into the cavity of the small pelvis, encounters fewer obstacles than the parietal bones located at the symphysis and cape. There comes a moment when the force necessary to lower the occiput becomes equal to the force necessary to overcome the friction of the head at the cape. From this moment, the selective lowering of one occiput into the small pelvis (flexion of the head) stops and other forces begin to act, contributing to the advancement of the entire head. There comes the most difficult and longest moment of the biomechanism of childbirth.
  • 3rd moment - sacral rotation (rotatio sacralis). The fetal head remains fixed at two main points at the symphysis and promontory. The sacral rotation is a pendulum movement of the head with an alternating deviation of the sagittal suture either closer to the pubis or closer to the promontory. A similar axial movement of the head occurs around the point of its strengthening on the cape. Due to the lateral inclination of the head, the place of the main application of the expelling force from the region of the sagittal suture is transferred to the anterior parietal bone (the force of its adhesion to the symphysis is less than that of the posterior parietal to the cape). The anterior parietal bone begins to overcome the resistance of the posterior surface of the symphysis, sliding along it and descending below the posterior parietal. At the same time, to a greater or lesser extent (depending on the size of the head), the anterior parietal bone is on the back. This thrusting occurs until the greatest convexity of the anterior parietal bone will not pass by the symphysis. After this, the posterior parietal bone slips off the cape, and it goes even more under the anterior parietal bone. At the same time, both parietal bones are pushed onto the frontal and occipital bones, and the entire head (in toto) descends into a wide part of the pelvic cavity. The sagittal suture at this time is located approximately in the middle between the symphysis and the promontory.

Thus, in the sacral rotation, 3 stages can be distinguished:

  • 1) lowering of the anterior and delay of the posterior parietal bone;
  • 2) slippage of the posterior parietal bone from the promontory;
  • 3) lowering the head into the pelvic cavity.
  • 4th moment - internal rotation of the head (rotatio capitis interna). Occurs in the cavity of the small pelvis: begins at the transition from the wide part to the narrow and ends at the pelvic floor. By the end of the sacral rotation, the head has passed the plane of entry into the small pelvis as a large segment, and its lower pole is in the interspinal plane. Thus, there are all conditions conducive to its rotation using the sacral cavity. Rotation is determined by the following factors:
    • 1) the shape and size of the birth canal, which has the form of a truncated pyramid, the narrowed part facing downwards, with a predominance of direct dimensions over transverse ones in the planes of the narrow part and exit from the small pelvis;
    • 2) the shape of the head, tapering in the direction of the frontal tubercles and having "convex" surfaces - the parietal tubercles.

The posterolateral part of the pelvis, in comparison with the anterior part, is narrowed by the muscles lining inner surface pelvic cavity. The occiput appears wider than frontal part heads. These circumstances favor turning the occiput anteriorly. In the internal rotation of the head, the parietal muscles of the small pelvis and the muscles of the pelvic floor, mainly a powerful paired muscle that lifts anus. The convex parts of the head (frontal and parietal tubercles) located on different height and located asymmetrically with respect to the pelvis, at the level of the spinal plane come into contact with the legs of the levators. The contraction of these muscles, as well as piriformis and internal obturator muscles, leads to a rotational movement of the head. The rotation of the head occurs around the longitudinal axis in the anterior view of the occiput presentation by 45 °. When the rotation is completed, the sagittal suture is set in the direct size of the exit plane from the small pelvis, the back of the head is facing anteriorly.

  • 5th moment - extension of the head (deflexio capitis) takes place in the plane of the exit from the small pelvis, i.e., on the pelvic floor. After completion of the internal rotation, the fetal head fits under the lower edge of the symphysis with the suboccipital fossa, which is the fixation point (punctum fixum, s. hypomochlion). Around this point, the head makes extension. The degree of extension of the previously bent head corresponds to an angle of 120--130°. The extension of the head occurs under the influence of two mutually perpendicular forces. On the one hand, expelling forces act through the fetal spine, and on the other, a lateral pressure force from the pelvic floor muscles. Having completed the extension, the head is born in the most favorable small oblique size, equal to 9.5 cm, and a circumference equal to 32 cm.
  • 6th moment - internal rotation of the body and external rotation of the head (rotatio trunci interna et rotatio capitis externa). After extension of the head, the fetal shoulders move from the wide part of the small pelvis to the narrow one, trying to occupy the maximum size of this plane and the exit plane. As well as on the head, they are affected by contractions of the pelvic floor muscles and parietal muscles of the small pelvis.

The shoulders make an internal turn, successively moving from transverse to oblique, and then to the direct size of the planes of the small pelvis. The internal rotation of the shoulders is transmitted to the born head, which makes an external rotation. External rotation of the head corresponds to the position of the fetus. In the first position, the turn is carried out with the back of the head to the left, the face to the right. In the second position, the back of the head turns to the right, the face - to the left thigh of the mother.

7th moment - the exit of the trunk and the entire body of the fetus (expulsio trunciet corporis totales). Anterior shoulder is placed under the symphysis. below head humerus(on the border of the upper and middle thirds of the humerus) fixation points are formed. The body of the fetus is bent lumbar-thoracic region, and the back shoulder and back handle are born first. After that, the front shoulder and the front handle roll out (born) from under the pubis, and the whole body of the fetus comes out without any difficulty.

The head of the fetus born in the anterior occipital presentation has a dolichocephalic shape due to the configuration and the birth tumor.

A birth tumor on the fetal head is formed due to serous-bloody impregnation ( venous congestion) soft tissues below the belt of contact of the head with the bone ring of the pelvis. This impregnation is formed from the moment the head is fixed at the entrance to the small pelvis due to the difference in pressure that acts on the head above and below the contact zone (72 and 94 mm Hg, respectively). A birth tumor can only occur in a living fetus; with timely outpouring of water, the tumor is insignificant, with premature - pronounced.

With occipital presentation, the birth tumor is located on the head closer to the leading point - the posterior (small) fontanel. By its location, you can recognize the position of the fetus in which the birth took place. In the first position, the birth tumor is located on the right parietal bone closer to the small fontanelle, in the second position, on the left parietal bone. childbirth hemolytic fetus pregnancy

Obstetricians today are quite experienced and can cope with any difficulties during labor.

Depending on the placement of the fetus, the doctor takes actions that will further affect the birth, as well as the health of the baby, so it is worth studying the presentation process in more detail.

About delivery in anterior occipital presentation

Biological childbirth is based on all the efforts and actions of the body of the mother and child, so that the fetus can pass through birth canal and will come to light. There are flexion, extensor and rotational actions of the body.

Occipital presentation is the position of the baby in the uterus, the head is in a bent position, and the back of the head is the lowest. Obstetricians have proven that a similar position of the child in the womb is also noted by 96% of all mothers before childbirth.

  1. Labor activity begins at the moment when the baby's head bends. During this stunt cervical spine bends, and meanwhile the chin is pressed against the chest, while the back of the head, on the contrary, is down. Usually the forehead can linger before entering the pelvis. Next - the entry of the head into the small pelvis.
  2. The second stage is the main one - this is the rotation of the baby's head inside the mother. The head moves along the pelvis. The back of the head comes closer to the pubic joint and runs along the side wall of the pelvis of the uterus.
  3. At the third stage of childbirth, the head should unbend and then goes its own way. In normal, natural childbirth, the head unbends when it exits the pelvis. Thanks to all of the above actions, in just a few seconds, the head can fully unbend. The baby's head passes through the vulvar ring.

In the fourth stage, the baby's shoulders turn inward. After the shoulders have emerged from the mother's womb, the baby comes out completely.

Many doctors claim that only in isolated cases, with this type of presentation, the child is born with the back of the head. This means that the baby's head comes out at the back of the head. The reason for this position of the child may be a change in the capacity of the small pelvis, bad condition muscles of the uterus, or in premature birth.

  1. The first stage of childbirth - the head bends and as a result, the swept suture becomes synclitic. The head passes the small pelvis.
  2. In the second stage, the baby's head turns incorrectly. The head makes a turn of 45-90 degrees and the small fontanel becomes behind the sacrum, and the large one is in front of the womb
  3. The third stage involves bending the head. The back of the head appears first, and then the head unbends during attempts. The forehead of the crumb appears, and then his face.

The birth of a child with a posterior occipital presentation is extremely dangerous, because there is a maximum flexion of the fetal head. This type childbirth is much more difficult, both for the woman in labor and for the baby, it requires much more time and effort.

The soft tissues of the perineum and uterus are greatly stretched in such cases. Unfortunately, such childbirth can not only adversely affect the health of the baby, but even lead to fetal asphyxia.

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