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 easy ways to measure 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.

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 pelvis (Fig. 1).

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. When the fetus passes through birth canal(through the plane of exit from the small pelvis) the coccyx deviates posteriorly, and this size increases by 1.5-2.0 cm, becoming equal to 11.0-11.5 cm. The transverse size is the distance between the inner surfaces of the ischial tuberosities. It is equal to 11.0 cm. Thus, largest size in the plane of the exit of the small pelvis - 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 transverse dimension is maximum, in the wide part of the pelvic cavity there is a conditionally allocated 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.

IN
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) 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 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.

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 the lumbar lordosis is 4.6 cm (according to Sh. Ya. Mikeladze).

As pregnancy progresses, it increases lumbar lordosis 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. 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 spines iliac bones, 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, which is especially important if the woman has a narrowing of the pelvis.

The angle of inclination of the pelvis can be reduced by lifting top part the torso of a lying woman, or in the position of the woman in labor on her back, bring her bent at the knees and hip joints legs, or place a pad under the sacrum. If the pole is located under the lower back, the angle of the pelvis increases.

SMALL PELVIS.

BIG PELIN

The large pelvis is much wider than the small one. Limited:

From the sides by the wings of the iliac bones,

Posteriorly – the last lumbar vertebrae,

In front - the lower part of the abdominal wall.

The pelvis is the bony part of the birth canal.

Back wall The pelvis consists of:

Sacrum and coccyx,

The lateral ones are formed by the ischial bones,

anterior – pubic bones and symphysis

Pelvic sections:

Cavity

IN pelvic cavity distinguish between wide and narrow parts.

In accordance with this, four planes of the pelvis are considered:

I – plane of entrance to the pelvis,

II – plane of the wide part of the pelvic cavity,

III – plane of the narrow part of the pelvic cavity,

IV – plane of exit of the pelvis.

I. Plane of entry into the pelvis has the following boundaries:

Front – top edge symphysis and upper inner edge of the pubic bones,

On the sides there are nameless lines,

Behind is the sacral promontory.

The entrance plane has the shape of a kidney or a transverse oval with a notch corresponding to the sacral promontory.

There are three sizes at the entrance to the pelvis:

Transverse,

Two obliques.

Straight size– the distance from the sacral promontory to the most prominent point on the inner surface of the symphysis pubis. This size is called obstetric, or true conjugate(conjugata vera). There is also an anatomical conjugate - the distance from the promontory to the middle of the upper inner edge of the symphysis; the anatomical conjugate is slightly (0.3-0.5 cm) larger than the obstetric conjugate. Obstetric, or true conjugate is 11 cm.

Transverse size– the distance between the most distant points of nameless lines. This size is 13-13.5 cm.

Oblique dimensions: right and left, which are equal to 12-12.5 cm.

Right oblique dimension - the distance from the right sacroiliac joint to the left iliopubic tubercle,

The left oblique dimension is from the left sacroiliac joint to the right iliopubic tubercle.

II. 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,

behind – the junction of the II and III sacral vertebrae.

In the wide part of the pelvic cavity, two sizes are distinguished: straight and transverse.

Straight size - from the junction of the II and III sacral vertebrae to the middle of the inner surface of the symphysis; equals 12.5 cm.

Transverse size – between the tips of the acetabulum; equals 12.5 cm.

There are no oblique dimensions in the wide part of the pelvic cavity because in this place the pelvis does not form a continuous bone ring. Oblique dimensions in the widest part of the pelvis are conditionally allowed (length 13 cm).

III. The plane of the narrow part of the pelvic cavity limited:

anteriorly by the lower edge of the symphysis,

from the sides - the spines of the ischial bones,

behind – the sacrococcygeal joint.

There are two sizes: straight and transverse.

Straight the size goes from the sacrococcygeal joint to the lower edge of the symphysis (apex of the pubic arch); equal to 11-11.5 cm.

Transverse size connects the ischial spines; equal to 10.5 cm.

IV. Pelvic exit plane has the following boundaries:

In front - the lower edge of the symphysis,

From the sides - the ischial tuberosities,

At the back is the tip of the coccyx.

There are two sizes of the pelvic outlet: straight and transverse.

Straight the size of the pelvic outlet goes from the top of the coccyx to the lower edge of the symphysis; it is equal to 9.5 cm. When the fetus passes through the small pelvis, the tailbone moves away by 1.5-2 cm and the direct size increases to 11.5 cm.

Transverse the size of the pelvic outlet connects the internal surfaces of the ischial tuberosities; = 11 cm.

Structure and purpose of the bony pelvis

The birth canal includes both the bony pelvis and soft fabrics birth canal (uterus, vagina, pelvic floor and external genitalia).

1. Bone pelvis. (Pelvis)

It is a combination of 4 bones:

2 x unnamed (ossa innominata)

Sacrum (os sacrum)

Coccyx (os coccygeum)

The innominate bones are connected to each other through the pubic articulation (symphysis), to the sacrum through the right and left sacroiliac joints (articulatio sacroiliac dextra et sinistra).

The coccyx is connected to the sacrum through the sacrococcygeal joint (acticulatio sacro-coccygeum).

The pelvis is divided into large and small

a) The pelvis is that part of the bone canal that is located above its innominate or border line (linea innominata, s. terminalis). The lateral walls are the iliac fossa of the innominate bones (fossa iliaca dextra et sinistra). The large pelvis is open in front, and limited in the back by the lumbar part of the spine (IV and V vertebrae).

The size of the small pelvis is judged by the size of the large pelvis.

b) The pelvis is that part of the bone canal that is located below the innominate or border line. Most important in an obstetric sense. Knowing its size is necessary to understand the biomechanism of childbirth. Moving in the pelvis, the fetus is subjected to the greatest loads - compression, rotation. Deformation of the bones of the fetal head is possible.

The walls of the small pelvis are formed: in front - by the inner surface of the symphysis pubis, on the sides - by the inner surfaces of the innominate bones, in the back - by the inner surface of the sacrum.

Classic pelvic planes

Pelvic planes:

a) plane of entrance to the pelvis;

b) the plane of the wide part;

c) the plane of the narrow part;

d) the plane of the pelvic outlet.

I. The boundaries of the plane of entrance to the small pelvis are the promontory of the sacrum, the innominate line and the upper edge of the symphysis.

Dimensions of the entrance to the pelvis:

1) Straight - true conjugata (conjugata vera) - from the most protruding point of the inner surface of the womb to the promontory of the sacrum - 11 cm.

2) Transverse size - connects the most distant points of the border line - 13-13.5 cm.

3) Two oblique dimensions: right - from the right sacroiliac joint to the left iliopubic tubercle (eminentia-iliopubica sinistra) and left - from the left sacroiliac joint to the right iliopubic tubercle.

Oblique dimensions are 12-12.5 cm.

Normally, the oblique dimensions are considered the dimensions of the typical insertion of the fetal head.

II. The plane of the wide part of the pelvic cavity.

The front boundaries are the middle of the inner surface of the symphysis pubis, the back is the line of connection of the 2nd and 3rd sacral vertebrae, the sides are the middle of the acetabulum (lamina accetabuli).

Dimensions of the wide part of the pelvic cavity:

straight size - from the upper edge of the 3rd sacral vertebra to the middle of the inner surface of the symphysis - 12.5 cm;

transverse size - between the midpoints of the acetabulum 12.5 cm;

oblique dimensions - conventionally from the upper edge of the greater sciatic notch (incisura ischiadica major) on one side to the groove of the obturator muscle (sulcus obturatorius) - 13 cm.

III. The plane of the narrow part of the pelvic cavity.

Borders: in front - the lower edge of the symphysis pubis, behind - the apex sacral bone, on the sides - the ischial spines (spinae ischii).

Dimensions of the narrow part of the pelvic cavity:

straight size - from the apex of the sacrum to the lower edge of the symphysis pubis (11-11.5 cm);

transverse size - line connecting the ischial spines - 10.5 cm.

IV. The plane of exit of the small pelvis.

Borders: in front - the pubic arch, behind - the apex of the coccyx, on the sides - the inner surfaces of the ischial tuberosities (tubera ischii).

Pelvic outlet dimensions:

straight size - from the lower edge of the pubic symphysis to the apex of the coccyx - 9.5 cm, with deviation of the coccyx - 11.5 cm;

transverse size - between the inner surfaces of the ischial tuberosities - 11 cm.

Pelvic wire line (pelvic axis).

If you connect the centers of all direct dimensions of the pelvis with each other, you get a concave anterior line, which is called the wire axis, or the pelvic line.

The wire axis of the pelvis first goes in the form of a straight line until it reaches the plane intersecting the lower edge of the symphysis, the so-called main one. From here, a little lower, it begins to bend, crossing at right angles a successive series of planes that go from the lower edge of the symphysis to the sacrum and coccyx. If this line is continued upward from the center of the entrance to the pelvis, it will cross abdominal wall in the navel area; if it is continued downwards, it will pass through the lower end of the coccyx. As for the axis of exit of the pelvis, then, being continued upward, it will cross the upper part of the first sacral vertebra.

The fetal head, when passing through the birth canal, cuts through a series of parallel planes with its circumference until it reaches the pelvic floor with a wire point. These planes through which the head passes are called parallel planes by Goji.

Of the parallel planes, the most important are the following four, which are spaced from each other at almost equal distances (3-4 cm).

The first (upper) plane passes through the terminal line (linea terminalis) and is therefore called the terminal plane.

The second plane, parallel to the first, intersects the symphysis at its lower edge - the inferior parallel plane. It is called the main plane.

The third plane, parallel to the first and second, intersects the pelvis in the spinae ossis ischii region - this is the spinal plane.

Finally, the fourth plane, parallel to the third, represents the pelvic floor, its diaphragm and almost coincides with the direction of the coccyx. This plane is usually called the output plane.

Pelvic inclination is the ratio of the plane of the entrance to the pelvis to the horizontal plane (55-60 degrees). The angle of inclination can be slightly increased or decreased by placing a cushion under the lower back and crosses for the lying woman.

Pelvic floor

The pelvic floor is a powerful muscular-fascial layer consisting of three layers.

I. Bottom (outer) layer.

1. Bulbocavernosus (m. bulbocavernosus) compresses the vaginal opening.

2. Ischio-cavernosus (m. ischocavernosus).

3. Superficial transverse muscle of the perineum (m. transversus perinei superficialis).

4. external sphincter of the anus (m. sphincter ani externus).

II. Middle layer- urogenital diaphragm (diaphragma urogenitale) - a triangular muscular-fascial plate located under the symphysis, in the pubic arch. Its posterior part is called the deep transverse muscle of the perineum (m. transversus perinei profundus).

III. The upper (inner) layer - the pelvic diaphragm (diaphragma pelvis) consists of a paired muscle, the levator anus(m. levator ani).

Functions of the muscles and fascia of the pelvic floor.

1. They support the internal genital organs and help preserve them normal position. During contraction, the genital fissure closes, narrowing the lumen of the rectum and vagina.

2. They support the viscera and participate in the regulation of intra-abdominal pressure.

3. During labor and expulsion, all three layers of the pelvic floor muscles stretch and form a wide tube, which is a continuation of the bony birth canal.

Obstetric (anterior) perineum - part of the pelvic floor between the posterior commissure of the labia and the anus.

The posterior perineum is the part of the pelvic floor, between the anus and the tailbone.

LITERATURE:

BASIC:

1. Bodyazhina V.I., Zhmakin K.N. Obstetrics, M., Medicine, 1995.

2. Malinovsky M.R. Operative obstetrics. 3rd ed. M., Medicine, 1974.

3. Serov V.N., Strizhakov A.N., Markin S.A. Practical obstetrics. M., Medicine, 1989. - 512 p.

4. Chernukha E.A. Maternity block. M., Medicine, 1991.

ADDITIONAL:

1. Abramchenko V.V. Modern methods preparing pregnant women for childbirth. S. Petersburg., 1991. - 255 p.

2. Doctor's Directory antenatal clinic. Ed. Gerasimovich G.I.

2. SMALL PELVIS. Planes and dimensions of the small pelvis (Table 3).

The pelvis is the bony part of the birth canal.

The posterior wall of the pelvis consists of the sacrum and coccyx, the side walls are formed by the ischial bones, the anterior wall by the pubic bones and the symphysis (Fig. 3, 4, 5).

The following sections exist in the pelvis:

2. Cavity:

1) wide part;

2) narrow part;

In accordance with this, four planes of the pelvis are considered:

1. I – plane of entrance to the pelvis,

2. II – plane of the wide part of the pelvic cavity,

3. III – plane of the narrow part of the pelvic cavity,

4. IV – plane of exit of the pelvis.

Rice. 3. Dimensions of the entrance to the small pelvis Fig. 4. Exit plane dimensions:

1 – straight; 2- transverse 1 – straight; 2-cross

3 – right oblique; 4- left oblique

Rice. 5. Sagittal section of the pelvis with the designation of the conjugate and the anteroposterior size of the pelvic outlet.

Table 3.

№	Name of planes	Plane boundaries	Plane dimensions	Size limits	Size values
1.	Plane of entry into the pelvis	1) in front - the upper edge of the symphysis and the upper inner edge of the pubic bones, 2) from the sides - innominate lines, 3) behind - the sacral promontory.	straight	from the sacral promontory to the most prominent point on the inner surface of the symphysis pubis. This size is called the obstetric, or true, conjugate (conjugata vera).	11 cm.
transverse	between the most distant points of nameless lines.	13-13.5 cm.
two oblique	The right oblique dimension is the distance from the right sacroiliac joint to the left iliopubic tubercle, the left oblique dimension is from the left sacroiliac joint to the right iliopubic tubercle.	12-12.5 cm.
№	Name of planes	Plane boundaries	Plane dimensions	Size limits	Size values
2.	The plane of the wide part of the pelvic cavity:	1) in front - the middle of the inner surface of the symphysis, 2) on the sides - the middle of the acetabulum, 3) behind - the junction of the II and III sacral vertebrae	straight	from the junction of the II and III sacral vertebrae to the middle of the inner surface of the symphysis;	12.5 cm.
transverse	between the tips of the acetabulum	12.5 cm
3.	The plane of the narrow part of the pelvic cavity	1) in front by the lower edge of the symphysis, 2) on the sides - by the spines of the ischial bones, 3) behind - by the sacrococcygeal joint.	straight	from the sacrococcygeal joint to the lower edge of the symphysis (apex of the pubic arch);	11-11.5 cm.
transverse	connects the spines of the ischial bones;	10.5 cm.
4.	Pelvic exit plane	1) in front - the lower edge of the symphysis, 2) from the sides - the ischial tuberosities, 3) in the back - the apex of the coccyx.	straight	goes from the top of the coccyx to the lower edge of the symphysis; When the fetus passes through the pelvis, the tailbone moves away by 1.5-2 cm	9.5 cm to 11.5 cm.
transverse	connects the inner surfaces of the ischial tuberosities;	11 cm.

The pelvis measurement is performed in mandatory to all pregnant women. This is a quick, painless and absolutely harmless procedure, the implementation of which is an indispensable condition for obtaining a pregnant woman’s card when a woman first contacts a gynecologist. Based on the following, you can plan the management of childbirth: naturally or surgical method(C-section). Timely choice of tactics allows you to avoid many complications that pose a threat to the life of a woman and her baby. A properly planned birth is a guarantee that the birth of a child will be easy and safe.

The true conjugate is the shortest promontory and the most protruding point into the pelvic cavity on the inner surface of the symphysis. Normally this distance is 11 cm.

What's happened

Taz like anatomical education represented by two pelvic bones and distal section spine (sacrum and coccyx). In obstetrics, only that part of it that is called the small pelvis is important. This is the space limited by the lower sections of the sacrum and coccyx. It contains the following organs: bladder, uterus and rectum. There are four main planes in its structure. Each of them has several sizes that are important in obstetric practice.

Parameters of entry into the pelvis

1. The size is straight. This indicator has other names - obstetric conjugate and true conjugate. Equal to 110 mm.
2. Transverse size. Equal to 130-135 mm.
3. The dimensions are oblique. Equal to 120-125 mm.
4. Diagonal conjugate. Equal to 130 mm.

Parameters of the wide part of the small pelvis

1. The size is straight. Equal to 125 mm.
2. Transverse size. Equal to 125 mm.

Parameters of the narrow part of the small pelvis

Pelvic outlet parameters

1. The size is straight. During childbirth, it may increase, as the fetal head moving along the birth canal bends the tailbone posteriorly. It is 95-115 mm.
2. Transverse size. Equal to 110 mm.

Measuring the pregnant pelvis

The above indicators are anatomical, that is, they can be determined directly from the pelvic bones. It is not possible to measure them on a living person. Therefore, in obstetric practice the most important parameters are:

1. The distance between the awns located at the anterior edge of the ridge.
2. The distance between the points of the iliac crests that are separated from each other by the maximum distance.
3. Distance between lugs femur in the area where their upper part transitions to the neck.
4. (distance from to the lumbosacral cavity).

Thus, the normal dimensions of the pelvis are 250-260, 280-290, 300-320 and 200-210 millimeters, respectively.

Clarification of these parameters is mandatory when registering a pregnant woman. The measurement is carried out with a special instrument (pelvic meter), which, by the way, can also be used to measure the head of a newborn baby.

It is important to understand that the volume of soft tissue does not affect the result of the study. The parameters of the pelvis are assessed by bony protrusions, and they do not shift anywhere when losing weight or, on the contrary, gaining weight. The size of the pelvis remains unchanged after a woman reaches the age when bone growth stops.

To diagnose pelvic narrowing, two more conjugates are important - true (obstetric) and diagonal. However, it is not possible to measure them directly; their size can only be judged indirectly. The diagonal conjugate in obstetrics is usually not measured at all. More attention is paid to the obstetric conjugate.

The determination of the true conjugate is carried out according to the formula: the size of the outer conjugate minus 9 centimeters.

What is a narrow pelvis?

Before talking about the definition of this term, it should be noted that there are two types of narrow pelvis - anatomical and clinical. These concepts, although not identical, are closely related to each other.

We should talk about an anatomically narrow pelvis when at least one of the parameters is smaller than the normal dimensions of the pelvis. There are degrees of narrowing when the true conjugate is less than normal:

• by 15-20 mm.
• 20-35 mm.
• 35-45 mm.
• more than 45 mm.

The last two degrees indicate the need for surgical intervention. A true conjugate of the 1st-2nd degree allows the possibility of continuing childbirth naturally, provided that there is no threat of a condition such as a clinically narrow pelvis.

Clinically, a narrow pelvis is a situation when the parameters of the fetal head do not correspond to the parameters of the mother’s pelvis. Moreover, all dimensions of the latter can be within normal limits (that is, from the point of view of anatomy this basin not always narrow). The opposite situation may also occur, when an anatomically narrow pelvis completely corresponds to the configuration of the fetal head (for example, if the child is small), and the diagnosis of a clinically narrow pelvis in in this case there is no question.

The main reasons for this condition:

1. On the maternal side: anatomically small pelvis, irregular pelvic shape (for example, deformation after injury).
2. From the side of the fetus: hydrocephalus, large size, tilting of the head when the fetus enters the pelvis.

Depending on how pronounced the difference is between the parameters of the maternal pelvis and the fetal head, three degrees of clinically narrow pelvis are distinguished:

1. Relative disparity. In this case independent childbirth possible, but the doctor must be ready to make a timely decision about surgical intervention.
2. Significant discrepancy.
3. Absolute discrepancy.

Childbirth with a clinically narrow pelvis

The second and third degrees are an indication for surgical intervention. Independent childbirth in this situation is impossible. The fruit can only be extracted when caesarean section.

If there is a relative discrepancy, natural childbirth is acceptable. However, one should remember the danger of changing the situation for the worse. The doctor must decide on the severity of the discrepancy during labor in order to make a timely decision. further tactics. Delayed diagnosis of conditions when delivery should only be performed surgically, can lead to serious difficulties with the removal of the fetal head. If there is a pronounced discrepancy, the latter will be driven into the pelvic cavity by the contracting uterus, which will lead to severe head injury and death. In advanced cases, it is impossible to extract the fetus alive from the pelvic cavity even if a cesarean section is performed. In such cases, childbirth has to be completed with a fetal destruction operation.

Let's sum it up

It is necessary to know the size of the pelvis. This is necessary in order to promptly suspect such pathological conditions, both anatomically and clinically narrow pelvis. Decrease normal sizes May be varying degrees expressiveness. In some cases, spontaneous childbirth is even possible; in other situations, it becomes necessary to perform a cesarean section.

Clinically narrow pelvis is a very insidious condition. It is not always combined with the concept of an anatomically narrow pelvis. The latter may have normal parameters, however, the possibility of a discrepancy between the size of the head and the size of the pelvis still exists. The occurrence of such a situation during childbirth can cause dangerous complications(First of all, the fetus will suffer). That's why it's so important timely diagnosis and quick decision-making on further tactics.