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Lines of female pelvis sizes with names. The pelvis from an obstetric point of view

Planes and dimensions of the small pelvis. The pelvis is the bony part of the birth canal. The posterior wall of the pelvis consists of the sacrum and coccyx, the lateral ones are formed by the ischial bones, and the anterior wall is formed by the pubic bones and the symphysis. The posterior wall of the pelvis is 3 times longer than the anterior one. The upper pelvis is a continuous, inflexible ring of bone. In the lower section, the walls of the small pelvis are not solid; they contain the obturator foramen and sciatic notches, bounded by two pairs of ligaments (sacrospinous and sacrotuberous). The small pelvis has the following sections: inlet, cavity and outlet. In the pelvic cavity there are wide and narrow parts (Table 5). In accordance with this, four planes of the small pelvis are distinguished: 1 - plane of the entrance to the pelvis; 2 - plane of the wide part of the pelvic cavity; 3 - plane of the narrow part of the pelvic cavity; 4 - plane of exit of the pelvis. Table 5

Pelvic plane	Dimensions, cm
Pelvic plane	direct	transverse	oblique
Entrance to the pelvis		13-13,5	12-12,5
Wide part of the pelvic cavity			13 (conditional)
Narrow part of the pelvic cavity	11-11,5		-
Pelvic outlet	9.5-11,5		-

1. The plane of entrance to the pelvis has the following boundaries: in front - the upper edge of the symphysis and the upper inner edge of the pubic bones, on the sides - innominate lines, behind - the sacral promontory. The entrance plane has the shape of a kidney or a transverse oval with a notch corresponding to the sacral promontory. Rice. 68. Dimensions of the entrance to the pelvis. 1 - direct size (true conjugate) II cm; 2-transverse size 13 cm; 3 - left oblique size 12 cm; 4 - right oblique size 12 cm. b) Transverse size - the distance between the most distant points of the nameless lines. It is 13-13.5 cm.

c) The right and left oblique dimensions are equal to 12-12.5 cm. The right oblique dimension is the distance from the right sacroiliac joint to the left iliopubic tubercle; left oblique dimension - from the left sacroiliac joint to the right iliopubic tubercle. In order to more easily navigate in the direction of the oblique dimensions of the pelvis in a woman in labor, M. S. Malinovsky and M. G. Kushnir proposed the following technique (Fig. 69): the hands of both hands are folded at right angles, with the palms facing upward; the ends of the fingers are brought closer to the outlet of the pelvis of the lying woman. The plane of the left hand will coincide with the left oblique size of the pelvis, the plane of the right - with the right.

Rice. 69. Technique for determining the oblique dimensions of the pelvis. The plane of the left arm coincides with the sagittal suture located in the left oblique dimension of the pelvis.2. The plane of the wide part of the pelvic cavity has the following boundaries: in front - the middle of the inner surface of the symphysis, on the sides - the middle of the acetabulum, in the back - the junction of the II and III sacral vertebrae. In the wide part of the pelvic cavity, two sizes are distinguished: straight and transverse. a) Direct size - from the junction of the II and III sacral vertebrae to the middle of the inner surface of the symphysis; it is 12.5 cm.
b) Transverse size - between the middle of the acetabulum; it is equal to 12.5 cm. There are no oblique dimensions in the wide part of the pelvic cavity, since in this place the pelvis does not form a continuous bone ring. Oblique dimensions in the widest part of the pelvis are allowed conditionally (length 13 cm).3. The plane of the narrow part of the pelvic cavity is limited in front by the lower edge of the symphysis, on the sides by the spines of the ischial bones, and behind by the sacrococcygeal joint. a) The straight dimension goes from the sacrococcygeal joint to the lower edge of the symphysis (apex of the pubic arch); it is equal to 11 - 11.5 cm.
b) The transverse dimension connects the spines of the ischial bones; it is equal to 10.5 cm.4. The plane of exit of the pelvis has the following boundaries: in front - the lower edge of the symphysis, on the sides - the ischial tuberosities, in the back - the apex of the coccyx. The pelvic exit plane consists of two triangular planes, the common base of which is the line connecting the ischial tuberosities. Rice. 70. Dimensions of the pelvic outlet. 1 - straight size 9.5-11.5 cm; 2 - transverse size 11 cm; 3 - coccyx. Thus, at the entrance to the pelvis, the largest dimension is the transverse one. In the wide part of the cavity, the straight and transverse dimensions are equal; The oblique size will be conventionally accepted as the largest. In the narrow part of the cavity and outlet of the pelvis, the straight dimensions are larger than the transverse ones. In addition to the above (classical) pelvic cavities (Fig. 71a), parallel planes are distinguished (Fig. 71b). The first is the upper plane, passes through the terminal line (linca terminalis innominata) and is therefore called the terminal plane. The second is the main plane, runs parallel to the first at the level of the lower edge of the symphysis. It is called the main one because the head, having passed this plane, does not encounter significant obstacles, since it has passed a solid bone ring. The third is the spinal plane, parallel to the first and second, intersects the pelvis in the spina ossis ischii region. The fourth is the exit plane, which is the bottom of the pelvis (its diaphragm) and almost coincides with the direction of the coccyx. Wiring axis (line) of the pelvis. All planes (classical) of the pelvis border in front with one or another point of the symphysis, and in the back - with different points of the sacrum or coccyx. The symphysis is much shorter than the sacrum and coccyx, so the planes of the pelvis converge anteriorly and fan out posteriorly. If you connect the middle of the straight dimensions of all the planes of the pelvis, you will get not a straight line, but a concave anterior (towards the symphysis) line (see Fig. 71a).

This line connecting the centers of all direct dimensions of the pelvis is called the pelvic axis. At first it is straight, and then it bends in the pelvic cavity according to the concavity of the inner surface of the sacrum. In the direction of the wire axis of the pelvis, the born fetus passes through the birth canal. Pelvic tilt. When the woman is in an upright position, the upper edge of the symphysis is below the sacral promontory; true Koyuga-ga forms an angle with the horizontal plane, which is normally 55-60°. The ratio of the pelvic inlet plane to the horizontal plane is called pelvic inclination (Fig. 72). The degree of pelvic tilt depends on your body type.

Rice. 72. Pelvic tilt. Pelvic tilt can vary in the same woman depending on physical activity and body position. Thus, by the end of pregnancy, due to the movement of the center of gravity of the body, the angle of inclination of the pelvis increases by 3-4°. A large angle of inclination of the pelvis predisposes during pregnancy to sagging of the abdomen due to the fact that the presenting part is not fixed at the entrance to the pelvis for a long time. In this case, labor proceeds more slowly, and incorrect insertion of the head and perineal ruptures are more common. The angle of inclination can be slightly increased or decreased by placing a cushion under the lower back and sacrum of a lying woman. When placing a cushion under the sacrum, the pelvic inclination decreases slightly; a raised lower back helps to slightly increase the pelvic inclination angle.

Determining the size of the pelvis is extremely important, since their decrease or increase can lead to significant disruption of the course of labor. The most important during childbirth are the dimensions of the small pelvis, which are judged by measuring certain dimensions of the large pelvis using a special instrument - a pelvis gauge. The size of the large pelvis is determined using a Martin pelvis gauge (Fig. 6).

Rice. 6. Martin Tazomer.

The tazomer has the shape of a compass equipped with a scale on which centimeter and half-centimeter divisions are marked. At the ends of the branches of the tazomer there are spherical formations (“buttons”), which are applied to the protruding points of the large pelvis, somewhat squeezing the subcutaneous fatty tissue. To measure the transverse size of the pelvic outlet, a pelvis meter with intersecting branches was designed.

The examined woman lies on her back on a hard couch with her legs brought together and extended at the knee and hip joints. The doctor stands to the right of the pregnant woman, facing her. The branches of the pelvis are taken in such a way that fingers I and II hold the buttons. The graduated scale faces upward. Using your index fingers, you feel for the points, the distance between which is to be measured, pressing the buttons of the spread pelvis meter branches against them. The value of the corresponding size is marked on the scale.

The transverse dimensions of the pelvis (distantia spinarum, distantia cristarum, distantia trochanterica) and the external pelvic conjugata - conjugata externa are measured. (Fig. 7, 8).

Rice. 7. Measuring the transverse dimensions of the pelvis (1 - distantia spinarum, 2 - distantia cristarum, 3 - distantia trochanterica).

1. Distantia spinarum- the distance between the anterosuperior iliac spines on both sides; this size is 25-26 cm.

2. Distantia cristarum- the distance between the most distant parts of the iliac crests, this size is 28-29 cm.

3. Distantia trochanterica- the distance between the greater trochanters of the femurs; this distance is 31-32 cm (Fig. 9).

In a normally developed pelvis, the difference between the transverse dimensions of the large pelvis is 3 cm. A smaller difference between these dimensions will indicate a deviation from the normal structure of the pelvis.

4. Conjugata externa- the distance between the middle of the upper outer edge of the symphysis and the articulation of the V lumbar and I sacral vertebrae. (Fig. 8).

To measure it, a woman should lie on her left side, bending her left leg at the knee and hip joints, and keep her right leg extended. The “button” of one branch of the pelvis is installed in the middle of the upper outer edge of the symphysis, the other end is pressed against the suprasacral fossa, which is located under the spinous process of the V lumbar vertebra, corresponding to the upper corner of the sacral rhombus. You can determine this point by sliding your fingers downwards along the spinous processes of the lumbar vertebrae. The fossa is easily identified under the protrusion of the spinous process of the last lumbar vertebra. The external conjugate is normally 20-21 cm.

Rice. 8. Measurement of the external conjugate.

The external conjugate is important - by its size one can judge the size of the true conjugate (the direct size of the entrance to the pelvis).

To determine the true conjugate, subtract 9 cm from the length of the outer conjugate. For example, if the outer conjugate is 20 cm, then the true one is 11 cm.

The difference between the external and true conjugate depends on the thickness of the bones (sacrum, symphysis) and soft tissues. To determine the thickness of a woman’s bones, measure the circumference of the wrist joint (Soloviev index) with a centimeter tape (Fig. 9).

Rice. 9. Measurement of the Solovyov index.

Its average value is 14 - 16 cm. With the Solovyov index less than 14 cm (thin bones), the difference between the external and true conjugate will be less, so 8 cm is subtracted from the external conjugate. With the Solovyov index greater than 16 cm (thick bones), the difference between the outer and true conjugate will be larger, so 10 cm is subtracted from it.

Example: The external conjugate is 21 cm, the Solovyov index is 16.5 cm. What is the true conjugate? Answer: 21 cm - 10 cm = 11 cm (norm).

You can also calculate the size of the true conjugate by measuring the diagonal (Fig. 10).

Rice. 10. Measuring diagonal conjugates.

Diagonal conjugate- this is the distance between the lower edge of the symphysis and the prominent point of the promontory. The easy accessibility of the cape indicates a decrease in the true conjugate. If the middle finger reaches the promontory, then press the radial edge of the second finger to the lower surface of the symphysis, feeling the edge of the arcuate ligament of the pubis. After this, the index finger of the left hand marks the place of contact of the right hand with the lower edge of the symphysis. With a normally developed pelvis, the size of the diagonal conjugate is 13 cm. In these cases, the cape is unattainable.

If the cape is reached, the diagonal conjugate is 12.5 cm or less. By measuring the size of the diagonal conjugate, the doctor determines the size of the true conjugate. To do this, subtract 1.5-2.0 cm from the size of the diagonal conjugate (this figure is determined taking into account the height of the symphysis, the level of the promontory, and the angle of inclination of the pelvis). The higher the symphysis, the greater the difference between the conjugates, and vice versa. When the height of the symphysis is 4 cm or more, 2 cm is subtracted from the value of the diagonal conjugate; when the height of the symphysis is 3.0-3.5 cm, 1.5 cm is subtracted. When the pelvic tilt angle is more than 50°, to determine the true conjugate, 2 is subtracted from the value of the diagonal conjugate cm. If the pelvic tilt angle is less than 45°, then subtract 1.5 cm.

There is another dimension of the large pelvis - lateral Kerner conjugate. This is the distance between the superior anterior and superior posterior iliac spines. Normally, this size is 14.5-15 cm. It is recommended to measure it with oblique and asymmetrical pelvises. In a woman with an asymmetrical pelvis, it is not the absolute size of the lateral conjugate that matters, but the comparison of their sizes on both sides.

If during examination of a woman there is a suspicion of a narrowing of the pelvis, then the dimensions of the exit plane are determined.

The dimensions of the pelvic outlet are determined as follows. The woman lies on her back, legs bent at the hip and knee joints, spread apart and pulled up to the stomach.

Straight exit plane size measured with a conventional pelvis meter (Fig. 11-a). One “button” of the pelvis gauge is pressed to the middle of the lower edge of the symphysis, the other to the top of the coccyx. In a normal pelvis, the size of the exit plane is 9.5 cm.

Rice. 11. Measuring the transverse (a) and direct (b) dimensions of the plane of entry into the pelvis.

Transverse dimension of the pelvic outlet plane(Fig. 11-b) - The distance between the inner surfaces of the ischial bones is quite difficult to measure. This size is measured with a centimeter or a pelvis with intersecting branches in the position of the woman on her back with her legs brought to her stomach. 1.5 cm is added to the resulting size. Normally, the transverse size of the pelvis is 11 cm.

In the same position, women measure the pubic angle to assess the characteristics of the small pelvis by placing the first fingers of their hands on the pubic arches. With normal size and shape of the pelvis, the angle is greater than 90 degrees.

Indirect signs of a correct physique and a normal pelvis are the shape and size of the sacral rhombus (Michaelis rhombus)(Fig. 12).

Rice. 12. Michaelis rhombus (a - general view: 1 - depression between the spinous processes of the last lumbar and first sacral vertebrae; 2 - apex of the sacrum; 3 - posterosuperior iliac spines; 6 - shapes of the Michaelis rhombus in a normal pelvis and various anomalies of the bony pelvis (diagram ): 1 - normal pelvis; 2 - flat pelvis; 3 - uniformly narrowed pelvis; 4 - transversely narrowed pelvis;

The sacral rhombus is a platform on the posterior surface of the sacrum. In women with a normally developed pelvis, its shape approaches a square, all sides of which are equal, and the angles are approximately 90°. A decrease in the vertical or transverse axis of the rhombus, asymmetry of its halves (upper and lower, right and left) indicate anomalies of the bony pelvis. The upper corner of the diamond corresponds to the spinous process of the V lumbar vertebra. The lateral angles correspond to the posterosuperior iliac spines, the lower angle corresponds to the apex of the sacrum (sacrococcygeal joint).

The dimensions of the rhombus are measured with a measuring tape. Normally, the longitudinal size is 11 cm, the transverse size is 10 - 11 cm. The dimensions of the length of the Michaelis rhombus correspond to the dimensions of the true conjugate.

Questions for self-control

1. What instrument is used to measure the size of the female pelvis?

2. List the 4 main pelvic sizes.

3. How to measure distantia spinarum? What is this size?

4. What is distantia cristarum equal to?

5. How to measure the intertrochanteric size (distantia trochanterica)?

6. How to correctly measure the external conjugate? What position should a woman be in?

7. For what purpose and how is the Solovyov index measured?

8. What is a lateral conjugate? For what purpose is it necessary to measure it?

9. How to measure the direct and transverse dimensions of the pelvic outlet? What are they equal to?

10. What is a Michaelis rhombus? What shape does it have?

11. Name 3 ways to calculate the true conjugate.

12. How to measure a diagonal conjugate? What is it equal to?

Small pelvis is the bony part of the birth canal. The shape and size of the small pelvis are very important during childbirth and determining the tactics of its management. With sharp degrees of narrowing of the pelvis and its deformations, childbirth through the natural birth canal becomes impossible, and the woman is delivered by cesarean section.

The posterior wall of the pelvis is made up of the sacrum and coccyx, the lateral ones are the ischial bones, and the anterior wall is made up of the pubic bones with the pubic symphysis. The upper part of the pelvis is a continuous ring of bone. In the middle and lower thirds the walls of the small pelvis are not solid. In the lateral sections there are large and small sciatic foramina (foramen ischiadicum majus et minus), limited respectively by the large and small sciatic notches (incisura ischiadica major et minor) and ligaments (lig. Sacrotuberale, lig sacrospinale). The branches of the pubic and ischial bones, merging, surround the obturator foramen (foramen obturatorium), which has the shape of a triangle with rounded corners.

In the small pelvis there are an entrance, a cavity and an exit. In the pelvic cavity there are wide and narrow parts. In accordance with this, four classic planes are distinguished in the small pelvis (Fig. 1).

The plane of entry into the pelvis in front it is limited by the upper edge of the symphysis and the upper inner edge of the pubic bones, on the sides by the arcuate lines of the iliac bones and behind by the sacral promontory. This plane has the shape of a transverse oval (or kidney-shaped). It distinguishes three sizes (Fig. 2): straight, transverse and 2 oblique (right and left). The direct dimension is the distance from the superior inner edge of the symphysis to the sacral promontory. This size is called true or obstetric conjugate (conjugate vera) and is equal to 11 cm. In the plane of the entrance to the small pelvis, an anatomical conjugate (conjugate anatomica) is also distinguished - the distance between the upper edge of the symphysis and the sacral promontory. The size of the anatomical conjugate is 11.5 cm. The transverse size is the distance between the most distant sections of the arcuate lines. It is 13.0-13.5 cm. The oblique dimensions of the plane of the entrance to the small pelvis are the distance between the sacroiliac joint of one side and the iliopubic eminence of the opposite side. The right oblique size is determined from the right sacroiliac joint, the left - from the left. These sizes range from 12.0 to 12.5 cm.

The plane of the wide guest of the pelvic cavity in front it is limited by the middle of the inner surface of the symphysis, on the sides - by the middle of the plates covering the acetabulum, in the back - by the junction of the II and III sacral vertebrae. In the wide part of the pelvic cavity there are 2 sizes: straight and transverse. Direct size - the distance between the junction of the II and III sacral vertebrae and the middle of the inner surface of the symphysis. It is equal to 12.5 cm. The transverse dimension is the distance between the middles of the internal surfaces of the plates covering the acetabulum. It is equal to 12.5 cm. Since the pelvis in the wide part of the cavity does not represent a continuous bone ring, oblique dimensions in this section are allowed only conditionally (13 cm each).

The plane of the narrow cavity of the pelvic cavity bounded in front by the lower edge of the symphysis, on the sides by the spines of the ischial bones, and behind by the sacrococcygeal

articulation. In this plane there are also 2 sizes. Straight size - the distance between the lower edge of the symphysis and the sacrococcygeal joint. It is equal to 11.5 cm. Transverse size - the distance between the spines of the ischial bones. It is 10.5 cm.

Plane of exit from the pelvis in front it is limited by the lower edge of the pubic symphysis, on the sides by the ischial tuberosities, and behind by the apex of the coccyx. Direct size is the distance between the lower edge of the symphysis and the tip of the coccyx. It is equal to 9.5 cm. When the fetus passes through the birth canal (through the plane of exit from the small pelvis), due to the posterior movement of the coccyx, this size increases by 1.5-2.0 cm and becomes equal to 11.0-11.5 cm Transverse size - the distance between the inner surfaces of the ischial tuberosities. It is equal to 11.0 cm.

When comparing the sizes of the small pelvis in different planes, it turns out that in the plane of the entrance to the small pelvis the transverse dimensions are maximum, in the wide part of the pelvic cavity the direct and transverse dimensions are equal, and in the narrow part of the cavity and in the plane of the exit from the small pelvis the direct dimensions are greater than the transverse ones .

In obstetrics, in some cases, the system is used parallel Goji planes . The first, or upper, plane (terminal) passes through the upper edge of the symphysis and the border (terminal) line. The second parallel plane is called the main plane and runs through the lower edge of the symphysis parallel to the first. The fetal head, having passed through this plane, does not subsequently encounter significant obstacles, since it has passed through a solid bone ring. The third parallel plane is the spinal plane. It runs parallel to the previous two through the spines of the ischial bones. The fourth plane - the exit plane - runs parallel to the previous three through the apex of the coccyx.

All classic planes of the pelvis converge anteriorly (symphysis) and fan out posteriorly. If you connect the midpoints of all straight dimensions of the small pelvis, you will get a line curved in the shape of a fishhook, which is called wire axis of the pelvis. It bends in the pelvic cavity according to the concavity of the inner surface of the sacrum. The movement of the fetus along the birth canal occurs in the direction of the pelvic axis.

Pelvic angle - this is the angle formed by the plane of the entrance to the pelvis and the horizon line. The angle of inclination of the pelvis changes as the center of gravity of the body moves. In non-pregnant women, the pelvic inclination angle is on average 45-46°, and lumbar lordosis is 4.6 cm (according to Sh. Ya. Mikeladze).

As pregnancy progresses, lumbar lordosis increases due to a shift of the center of gravity from the area of the II sacral vertebra anteriorly, which leads to an increase in the angle of inclination of the pelvis. As lumbar lordosis decreases, the pelvic inclination angle decreases. Up to 16-20 weeks. During pregnancy, no changes are observed in the position of the body, and the angle of inclination of the pelvis does not change. By the gestational age of 32-34 weeks. lumbar lordosis reaches (according to I.I. Yakovlev) 6 cm, and the pelvic inclination angle increases by 3-4°, amounting to 48-50° (Fig. 5).

The angle of inclination of the pelvis can be determined using special instruments designed by Sh. Ya. Mikeladze, A. E. Mandelstam, as well as manually. With the woman lying on her back on a hard couch, the doctor places her hand (palm) under the lumbosacral lordosis. If the hand moves freely, then the angle of inclination is large. If the hand does not pass, the pelvic inclination angle is small. You can judge the angle of inclination of the pelvis by the relationship between the external genitalia and the hips. With a large angle of inclination of the pelvis, the external genitalia and genital cleft are hidden between the closed thighs. With a low angle of inclination of the pelvis, the external genitalia are not covered by closed thighs.

You can determine the angle of inclination of the pelvis by the position of both iliac spines relative to the pubic joint. The angle of inclination of the pelvis will be normal (45-50°) if, with the woman’s body in a horizontal position, the plane drawn through the symphysis and the upper anterior iliac spines is parallel to the horizontal plane. If the symphysis is located below the plane drawn through the indicated spines, the angle of inclination of the pelvis is less than normal.

The small angle of inclination of the pelvis does not prevent the fixation of the fetal head in the plane of the entrance to the small pelvis and the advancement of the fetus. Childbirth proceeds quickly, without damage to the soft tissues of the vagina and perineum. A large pelvic inclination angle often presents an obstacle to fixation of the head. Incorrect insertion of the head may occur. During childbirth, injuries to the soft birth canal are often observed. By changing the position of the mother's body during childbirth, it is possible to change the angle of inclination of the pelvis, creating the most favorable conditions for the advancement of the fetus along the birth canal.

The angle of inclination of the pelvis can be reduced by lifting the upper part of the body of a lying woman, or by placing the woman in labor on her back, bringing her legs bent at the knees and hip joints to her stomach, or placing a pad under the sacrum. If the pole is located under the lower back, the angle of the pelvis increases.

A - head above the entrance to the pelvis

B - head as a small segment at the entrance to the pelvis

B - head with a large segment at the entrance to the pelvis

G - head in the wide part of the pelvic cavity

D - head in the narrow part of the pelvic cavity

E - head at the pelvic outlet

The head is movable above the entrance.

In the fourth step of the obstetric examination, it is determined in its entirety (between the head and the upper edge of the horizontal branches of the pubic bones, you can freely bring the fingers of both hands), including its lower pole. The head moves, that is, it easily moves to the sides when it is pushed away during external examination. During vaginal examination, it is not achieved, the pelvic cavity is free (the boundary lines of the pelvis, promontory, inner surface of the sacrum and symphysis can be palpated), it is difficult to reach the lower pole of the head if it is fixed or shifted downward with an externally located hand. As a rule, the sagittal suture corresponds to the transverse size of the pelvis; the distances from the promontory to the suture and from the symphysis to the suture are approximately the same. The large and small fontanelles are located on the same level.

If the head is located above the plane of the entrance to the pelvis, its insertion is absent.

The head is a small segment at the entrance to the small pelvis (pressed against the entrance to the small pelvis). In the fourth step, it is palpated all over the entrance to the pelvis, with the exception of the lower pole, which has passed the plane of the entrance to the pelvis and which the examining fingers cannot cover. The head is fixed. It can be moved up and to the sides when applying a certain force (it is better not to try to do this). During an external examination of the head (both with flexion and extension insertions), the palms of the hands fixed on the head will diverge, their projection in the pelvic cavity represents the tip of an acute angle or wedge. With occipital insertion, the area of the back of the head accessible to palpation is 2.5-3.5 transverse fingers above the ring line and from the front part - 4-5 transverse fingers. During vaginal examination, the pelvic cavity is free, the inner surface of the symphysis is palpated, the promontorium is difficult to reach with a bent finger or is unreachable. The sacral cavity is free. The lower pole of the head may be accessible for palpation; when pressing on the head, it moves upward outside the contraction. The large fontanel is located above the small one (due to the flexion of the head). The sagittal suture is located transversely (it can form a small angle with it).

The head is a large segment at the entrance to the small pelvis.

The fourth technique determines only a small part of it above the entrance to the pelvis. During external examination, the palms, tightly applied to the surface of the head, converge at the top, forming with their projection an acute angle outside the large pelvis. The part of the back of the head is determined by 1-2 transverse fingers, and the front part - by 2.5-3.5 transverse fingers. During vaginal examination, the upper part of the sacral cavity is filled with the head (palpation is inaccessible to the promontory, the upper third of the symphysis and the sacrum). The sagittal suture is located in the transverse dimension, but sometimes with small sizes of the head one can also notice its beginning rotation. The cape is unreachable.

The head is in the wide part of the pelvic cavity.

During external examination, the head is not determined (the occipital part of the head is not determined), the front part is determined by 1-2 transverse fingers. During vaginal examination, the sacral cavity is filled in most of it (the lower third of the inner surface of the pubic joint, the lower half of the sacral cavity, the IV and V sacral vertebrae and the ischial spines are palpated). The contact zone of the head is formed at the level of the upper half of the pubic symphysis and the body of the first sacral vertebra. The lower pole of the head (skull) may be at the level of the apex of the sacrum or slightly lower. The arrow-shaped seam can be in one of the oblique sizes.

The head is in the narrow part of the pelvic cavity.

During vaginal examination, the head is easily reached, the sagittal suture is oblique or straight. The inner surface of the pubic joint is unreachable. Pushing activity began.

The head is on the pelvic floor or at the pelvic outlet.

External examination fails to identify the head. The sacral cavity is completely filled. The lower pole of contact of the head passes at the level of the apex of the sacrum and the lower half of the pubic symphysis. The head is located immediately behind the genital slit. Arrow-shaped seam in straight size. When pushing, the anus begins to open and the perineum protrudes. The head, located in the narrow part of the cavity and at the outlet of the pelvis, can also be felt by palpating it through the tissue of the perineum.

According to external and internal studies, a coincidence is observed in 75-80% of examined women in labor. Different degrees of flexion of the head and displacement of the skull bones (configuration) can change the data of the external examination and serve as an error in determining the insertion segment. The higher the experience of the obstetrician, the fewer errors are made in determining the segments of head insertion. The vaginal examination method is more accurate.

There are two sections of the pelvis: the large pelvis and the small pelvis. The boundary between them is the plane of the entrance to the small pelvis.

The large pelvis is bounded laterally by the wings of the ilium, and posteriorly by the last two lumbar vertebrae. In front it has no bony walls and is limited by the anterior abdominal wall.

The small pelvis is of greatest importance in obstetrics. The birth of the fetus occurs through the small pelvis. There are no simple ways to measure the pelvis. At the same time, the dimensions of the large pelvis are easy to determine, and on their basis one can judge the shape and size of the small pelvis.

The pelvis is the bony part of the birth canal. The shape and size of the small pelvis are very important during childbirth and determining the tactics of its management. With sharp degrees of narrowing of the pelvis and its deformations, childbirth through the natural birth canal becomes impossible, and the woman is delivered by cesarean section.

The posterior wall of the pelvis is made up of the sacrum and coccyx, the lateral ones are the ischial bones, and the anterior wall is made up of the pubic bones with the pubic symphysis. The upper part of the pelvis is a continuous ring of bone. In the middle and lower thirds the walls of the small pelvis are not solid. In the lateral sections there are large and small sciatic foramina (foramen ischiadicum majus et minus), limited respectively by the large and small sciatic notches (incisure ischiadica major et minor) and ligaments (lig. sacrotuberale, lig. sacrospinale). The branches of the pubic and ischial bones, merging, surround the obturator foramen (foramen obturatorium), which has the shape of a triangle with rounded corners.

The plane of entry into the pelvis in front it is limited by the upper edge of the symphysis and the upper inner edge of the pubic bones, on the sides by the arcuate lines of the iliac bones and behind by the sacral promontory. This plane has the shape of a transverse oval (or kidney-shaped). It comes in three sizes (Fig. 2): straight, transverse and 2 oblique (right and left). The direct dimension is the distance from the superior inner edge of the symphysis to the sacral promontory. This size is called true or obstetricconjugates(conjugata vera) and is equal to 11 cm. This size is of utmost importance in obstetrics, since on the basis of this value the degree of narrowing of the pelvis is judged.

In the plane of the entrance to the small pelvis there are also anatomicalconjugate(conjugata anatomica) - the distance between the upper edge of the symphysis and the sacral promontory. The size of the anatomical conjugate is 11.5 cm. The transverse size is the distance between the most distant sections of the arcuate lines. It is 13 cm. The oblique dimensions of the plane of entrance to the small pelvis are the distance between the sacroiliac joint of one side and the iliopubic eminence of the opposite side. The right oblique size is determined from the right sacroiliac joint, the left - from the left. These dimensions are 12 cm. Thus, in the plane of the entrance to the pelvis, the largest transverse dimension is.

P flatness of the wide part of the pelvic cavity in front it is limited by the middle of the inner surface of the symphysis, on the sides - by the middle of the plates covering the acetabulum, in the back - by the junction of the II and III sacral vertebrae. In the wide part of the pelvic cavity there are 2 sizes: straight and transverse. Direct size is the distance between the junction of the II and III sacral vertebrae and the middle of the inner surface of the symphysis. It is equal to 12.5 cm. The transverse dimension is the distance between the middles of the internal surfaces of the plates covering the acetabulum. It is equal to 12.5 cm. Since the pelvis in the wide part of the cavity does not represent a continuous bone ring, oblique dimensions (from the middle of the obturator foramen to the middle of the greater sciatic notch) in this section are allowed only conditionally (13 cm each). Thus, the largest dimensions in the plane of the wide part are oblique.

The plane of the narrow part of the pelvic cavity bounded in front by the lower edge of the symphysis, on the sides by the spines of the ischial bones, and behind by the sacrococcygeal joint. In this plane there are also 2 sizes. Straight size - the distance between the lower edge of the symphysis and the sacrococcygeal joint. It is equal to 11.5 cm. Transverse size - the distance between the spines of the ischial bones. It is 10.5 cm. In the plane of the narrow part of the pelvis, the largest dimension is the straight line.

Plane of exit from the pelvis(Fig. 3) in front it is limited by the lower edge of the pubic symphysis, on the sides by the ischial tuberosities, and behind by the apex of the coccyx. Direct size is the distance between the lower edge of the symphysis and the tip of the coccyx. It is equal to 9.5 cm. As the fetus passes through the birth canal (through the plane of exit from the pelvis), the tailbone deviates posteriorly, and this size increases by 1.5-2.0 cm, becoming equal to 11.0-11.5 cm. Transverse size - the distance between the inner surfaces of the ischial tuberosities. It is equal to 11.0 cm. Thus, the largest dimension in the plane of the pelvic outlet is straight.

When comparing the sizes of the small pelvis in different planes, it turns out that in the plane of the entrance to the small pelvis the maximum is the transverse dimension, in the wide part of the pelvic cavity there is a conventionally distinguished oblique dimension, and in the narrow part of the cavity and in the plane of the exit from the small pelvis the straight dimensions are larger than the transverse ones . Therefore, the fetus, passing through the planes of the pelvis, is installed with a sagittal suture in the maximum size of each plane.

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in obstetrics, in some cases the system is used parallel Goji planes(Fig. 4). The first, or upper, plane (terminal) passes through the upper edge of the symphysis and the border (terminal) line. The second parallel plane is called the main (cardinal) and runs through the lower edge of the symphysis parallel to the first. The fetal head, having passed through this plane, does not subsequently encounter significant obstacles, since it has passed through a solid bone ring. The third parallel plane is the spinal plane. It runs parallel to the previous two through the spines of the ischial bones. The fourth plane, the exit plane, runs parallel to the previous three through the apex of the coccyx.

All classic planes of the pelvis converge anteriorly (symphysis) and fan out posteriorly. If you connect the midpoints of all straight dimensions of the small pelvis, you will get a line curved in the shape of a fishhook, which is called wired pelvic axis. It bends in the pelvic cavity according to the concavity of the inner surface of the sacrum. The movement of the fetus along the birth canal occurs in the direction of the pelvic axis.

As pregnancy progresses, lumbar lordosis increases due to a shift in the center of gravity from the area of the II sacral vertebra anteriorly, which leads to an increase in the angle of inclination of the pelvis. As lumbar lordosis decreases, the pelvic inclination angle decreases. Until 16-20 weeks of pregnancy, no changes are observed in the position of the body, and the angle of the pelvis does not change. By the gestation period of 32-34 weeks, lumbar lordosis reaches (according to I. I. Yakovlev) 6 cm, and in
The goal of pelvic inclination increases by 3-4°, amounting to 48-50°( rice. 5 ).The magnitude of the pelvic inclination angle can be determined using special devices designed by Sh. Ya. Mikeladze, A. E. Mandelstam, as well as manually. With the woman lying on her back on a hard couch, the doctor places her hand (palm) under the lumbosacral lordosis. If the hand moves freely, then the angle of inclination is large. If the hand does not pass, the pelvic inclination angle is small. You can judge the angle of inclination of the pelvis by the ratio of the external genitalia and hips. With a large angle of inclination of the pelvis, the external genitalia and genital cleft are hidden between the closed thighs. With a low angle of inclination of the pelvis, the external genitalia are not covered by closed thighs.

You can also determine the angle of inclination of the pelvis by the position of both iliac spines relative to the pubic joint. The angle of inclination of the pelvis will be normal (45-50°) if, with the woman’s body in a horizontal position, the plane drawn through the symphysis and the upper anterior iliac spines is parallel to the horizontal plane. If the symphysis is located below the plane drawn through the indicated spines, the angle of inclination of the pelvis is less than normal.