Measure the outer dimensions of the pelvis. If it is impossible to palpate the trochanters of the femur due to excess weight, then it is necessary to ask the pregnant woman to move her feet and fix the movement of the trochanter on the thigh

During pregnancy, gynecologists pay increased attention to the size of the pelvis of the expectant mother. In our article, we will look at what the norms should be for natural childbirth, as well as what to do if you have a deviation from the norm.

Measuring the size of the pelvis during pregnancy

A mandatory procedure is to determine the size of this area. This is necessary to determine whether a natural resolution is possible or whether surgical intervention will have to be resorted to.

Important! To determine the internal narrowing, obstetricians measure the coverage of the wrist using the Solovyov index: if the girth exceeds 14 cm, then a narrow pelvis can be assumed.

The structure and measurements are determined by doctors by palpation and using a tazomer. The measurement is carried out several times: first, when a woman is registered for registration, and then before the birth itself. Particular attention is paid to the study of the sacral region - the Michaelis rhombus. To do this, measurements are taken between the dimples above the coccyx. If the rhombus is a square, the diagonals of which are approximately 11 cm, then we can conclude that there is no deformation. If they are different, then it can be assumed that the pregnant woman has a pathology.
Measurements are carried out as follows:

1. The woman should lie on her back, provide access to the hips, remove clothing from this area.
2. Using a pelvis meter, the doctor takes 1 longitudinal and 3 transverse measurements.

After the end of the procedure, the results are compared with acceptable indicators:

• Distantia spinarum- the line between the anterior superior iliac spines is approximately 26 cm;
• Distantia cristarum- the greatest distance between the scallops of the iliac bones - 24-27 cm;
• Distantia trochanterica- the line between the large skewers of the thigh bones - 28-29 cm;
• Conjugata externa- lines between the upper edge of the pubic joint and the V-lumbar vertebra - 20-21 cm.

Normal parameters of the pelvis

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narrow pelvis

Consider when it is considered narrowed, and what to do with such a pathology for a pregnant woman.

Did you know? Only in 5% of cases, children are born on time. In other cases, childbirth occurs 7-10 days earlier than the expected date.

First, it is worth noting that it is customary to distinguish two concepts - anatomically and clinically narrow pelvis. An anatomically narrow pelvis is characterized by a decrease in indicators when measured by at least 1.5-2 cm. In some situations, childbirth proceeds well - this happens if the child has a small head. A clinically narrow pelvis may well correspond to normal measurements, but due to the fact that the child may have a large head, there is a discrepancy between the head and the pelvis. In such a situation, childbirth can cause difficulties in the health of the mother and baby, so doctors often consider the possibility of an operation.

The reasons

The main causes of an anatomically narrow pelvis include:

• the presence of rickets;
• poor nutrition in childhood;
• the presence of poliomyelitis;
• the presence of congenital anomalies;
• the presence of pelvic fractures;
• the presence of tumors;
• the presence of kyphosis, scoliosis, spondylolisthesis and other deformities of the spine and coccyx;
• the presence of diseases and dislocations of the hip joints;
• rapid growth during puberty with elevated androgen levels;
• the presence of strong psycho-emotional and physical stress in adolescence.

Influence on the course of pregnancy

The presence of pathology almost does not affect the course of pregnancy. If an anatomically narrowed pelvis is present, you should definitely see a doctor. In the last trimester, some difficulties often arise, for example, the wrong position of the child. Since the head is not able to press against the entrance to the small pelvis due to the fact that it is narrow, a woman may suffer from shortness of breath.

Management of pregnancy

Women with pathology are put on a special account. This is due to the fact that there is a high risk of complications during pregnancy. Difficulties in management lie in the fact that it is very important to identify the abnormal position of the fetus in time. Also, the term of childbirth is determined with particular accuracy - this will eliminate overwearing, which negatively affects the general condition of the woman and the baby. Approximately 1-2 weeks before delivery, it is recommended to hospitalize the pregnant woman in order to clarify the diagnosis and choose the method of delivery.

Indications for caesarean section

There are two types of indications for intervention. Let's consider them. Absolute readings:

• the presence of a narrow pelvis of 3 and 4 degrees;
• the presence of severe pelvic deformity;
• damage to the joints of the pelvic bones;
• the presence of bone tumors.

In the presence of at least one of the above cases, natural delivery is strictly prohibited. In such situations, a planned caesarean section is prescribed.

Important! During contractions, women with a similar pathology are advised to lie more so as not to damage the amniotic sac, as it can provoke too early outflow of amniotic fluid.

Relative indications are the presence of a narrowed pelvis of the 1st degree simultaneously with the following factors:

• big fruit;
• presentation in the pelvic region;
• excess of terms of pregnancy;
• child's suffocation;
• uterine scar;
• abnormal deviations of the genital organs.

Also, an indication for surgical intervention is the presence of a narrowed pelvis of the 2nd degree. The difference between relative indications and absolute ones is that with them they can be allowed to give birth naturally and a cesarean section will be performed if the woman begins to feel unwell, or if there is a threat to the life of the mother and child.

Possible complications during childbirth

Unfortunately, in the presence of an anatomically narrow pelvis, it is impossible to give birth on your own. This is due to the fact that it is very difficult for a child to overcome the path, and this can lead to injuries and even death. It is for these reasons that obstetricians strongly advise women with this pathology to perform a planned caesarean section. However, if grade 1 narrowing is present, the expectant mother may be allowed to give birth on her own.

But such a decision can lead to:

• early rupture of amniotic fluid;
• weakened activity in childbirth;
• placental abruption;
• rupture of the pelvic ligaments;
• uterine rupture;
• hemorrhages;
• fetal suffocation;
• trauma to the baby.

Did you know? A newborn baby has 300 bones, while an adult has only 206.

A narrow pelvis is a specific feature of the structure of the female body. But even with such a pathology, modern medicine allows you to endure pregnancy and give birth to a child. The main thing is to follow the instructions of the doctor and take care of yourself.

Video: female pelvis during pregnancy

The plan of examination of a pregnant woman necessarily includes a measurement of the pelvis. This procedure is often carried out at the first appointment for every woman who has turned to an obstetrician-gynecologist about a desired pregnancy. The bone pelvis and the soft tissues lining it are the birth canal through which the baby is born. It is extremely important for doctors and a woman to know if the birth canal is small for a baby. This circumstance determines the possibility of childbirth through the natural birth canal. The results of the pelvic examination are included in the medical records. So that you can understand what is written on your exchange card, we will talk in detail about what the doctor does when measuring the pelvis of a pregnant woman.

Pelvic measurement during pregnancy

The structure and size of the pelvis are crucial for the course and outcome of childbirth. Deviations in the structure of the pelvis, especially a decrease in its size, complicate the course of childbirth or present insurmountable obstacles for them.

The study of the pelvis is carried out by inspection, palpation and measurement. During examination, attention is paid to the entire pelvic region, but special importance is attached to the sacral rhombus (Michaelis rhombus, Fig. 1), the shape of which, in combination with other data, allows one to judge the structure of the pelvis (Fig. 2).

Rice. 1. Sacral rhombus, or Michaelis rhombus

Rice. 2. Pelvic bones

The most important of all methods of examination of the pelvis is its measurement. Knowing the size of the pelvis, one can judge the course of childbirth, possible complications in them, the admissibility of spontaneous childbirth with a given shape and size of the pelvis. Most of the internal dimensions of the pelvis are not available for measurement, therefore, the external dimensions of the pelvis are usually measured and they are used to approximately judge the size and shape of the small pelvis. The pelvis is measured with a special instrument - a pelvis meter. The tazomer has the form of a compass, equipped with a scale on which centimeter and half-centimeter divisions are applied. At the ends of the branches of the tazomer there are buttons; they are applied to the places, the distance between which is to be measured. The following sizes of the pelvis are usually measured: (Latin names and abbreviations are indicated in brackets, since the sizes are indicated in the exchange card in this way.)

Spinarum distance (DistantiasplnarumD.sp.) - the distance between the anterior-superior iliac spines. This size is usually 25-26 cm (Fig. 3).

Rice. 3. Measuring the spinarum distance

Cristarum distance (Distantiacristarum D. Cr.) - the distance between the most distant points of the iliac crests. It averages 28-29 cm (Fig. 4).

Rice. 4. Measuring the distance of the cristarum

Distance trianterica (DistantiatrochantericaD. Tr.) - the distance between the large skewers of the femur. This size is 31 -32 cm (Fig. 5).

Rice. 5. Measuring the distance of the triangular

External conjugate (Conjugata externa C. Ext.) - external conjugate, i.e. straight size of the pelvis. To do this, the woman is laid on her side, the underlying leg is bent in

hip and knee joints, overlying pull. The external conjugate is normally 20–21 cm (Fig. 6).

Rice. 6. Measurement of external conjugates

The external conjugate is important: by its size, one can judge the size of the true conjugate - the distance between the sacral promontory - the most protruding point inside the sacrum and the most protruding point on the inner surface of the pubic symphysis (the junction of the pubic bones). This is the smallest dimension inside the pelvis through which the fetal head passes during childbirth. If the true conjugate is less than 10.5 cm, then childbirth through the natural birth canal may be difficult or simply impossible; in this case, a caesarean section is often performed. To determine the true conjugate, 9 cm is subtracted from the length of the outer conjugate. For example, if the outer conjugate is 20 cm, then the true conjugate is 11 cm; if the outer conjugate is 18 cm long, then the true conjugate is 9 cm, and so on. The difference between the outer and true conjugates depends on the thickness of the sacrum, symphysis and soft tissues. The thickness of the bones and soft tissues in women is different, so the difference between the size of the outer and true conjugate is not always exactly 9 cm. The true conjugate can be more accurately determined by the diagonal conjugate.

Diagonal conjugate (conju-gatadiagonalis) is the distance from the lower edge of the symphysis to the most prominent point of the promontory of the sacrum. The diagonal conjugate is determined during a vaginal examination of a woman (Fig. 7). The diagonal conjugate with a normal pelvis is on average 12.5-13 cm. To determine the true conjugate, 1.5-2 cm is subtracted from the size of the diagonal conjugate.

Rice. 7. Diagonal Conjugate Measurement

The doctor is not always able to measure the diagonal conjugate, because with normal pelvic dimensions during vaginal examination, the cape of the sacrum is not reached by the researcher's finger or is palpated with difficulty. If, during a vaginal examination, the doctor does not reach the cape, the volume of this pelvis can be considered normal. The dimensions of the pelvis and the external conjugate are measured in all pregnant women and women in labor without exception.

If during the examination of a woman there is a suspicion of a narrowing of the pelvic outlet, then the dimensions of this cavity are determined. These measurements are not mandatory, and they are measured in a position in which the woman lies on her back, her legs are bent at the hip and knee joints, spread apart and pulled up to her stomach.

The definition of the shape of the pubic angle is important. With normal pelvic dimensions, it is 90-100. The shape of the pubic angle is determined by the following method. The woman lies on her back, her legs are bent and pulled up to her stomach. With the palmar side, the thumbs are applied close to the lower edge of the symphysis. The location of the fingers allows you to judge the magnitude of the angle of the pubic arch.

Additional Research

If necessary, to obtain additional data on the size of the pelvis, its compliance with the size of the fetal head, deformities of the bones and their joints, an X-ray examination of the pelvis is performed - X-ray pelviometry. Such a study is possible at the end of the third trimester of pregnancy, when all the organs and tissues of the fetus are formed and an X-ray examination will not harm the baby. This study is carried out in the position of a woman lying on her back and on her side, which allows you to establish the shape of the sacrum, pubic and other bones; a special ruler determines the transverse and direct dimensions of the pelvis. The head of the fetus is also measured, and on this basis it is judged that its size corresponds to the size of the pelvis.

The size of the pelvis and its correspondence to the size of the head can be judged by the results of an ultrasound examination. This study allows you to measure the size of the fetal head, determine how the fetal head is located, because in cases where the head is unbent, that is, the forehead or face is present, it needs more space than in cases where the back of the head is present. Fortunately, in most cases, childbirth takes place in the occipital presentation.

Pelvic measurement is mandatory for all pregnant women. This is a quick, painless and absolutely harmless procedure, the implementation of which is an indispensable condition for issuing a pregnant card at the first visit of a woman to a gynecologist. Focusing on, you can plan the management of childbirth: naturally or surgically (caesarean section). A timely chosen tactic avoids many complications that pose a threat to the life of a woman and her baby. Properly planned childbirth is a guarantee that the birth of a child will be easy and safe.

The true conjugate is the shortest distance between the cape and the most prominent point in the pelvic cavity on the inner surface of the symphysis. Normally, this distance is 11 cm.

What

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

Parameters of entry into the small pelvis

1. Straight size. This indicator has other names - the obstetric conjugate and the true conjugate. Equal to 110 mm.
2. Cross size. Equal to 130-135 mm.
3. The sizes are oblique. Equal 120-125 mm.
4. Diagonal conjugate. Equal to 130 mm.

Parameters of the wide part of the small pelvis

1. Straight size. Equal to 125 mm.
2. Cross size. Equal to 125 mm.

Parameters of the narrow part of the small pelvis

Pelvic exit parameters

1. Straight size. During childbirth, it can increase, as the head of the fetus moving along the birth canal bends the coccyx backwards. It is 95-115 mm.
2. Cross size. Equal to 110 mm.

Measurement of the pelvis of a pregnant woman

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 following parameters are the most important:

1. The distance between the awns located at the front edge of the ridge.
2. The distance between the points of the iliac crests that are at the maximum distance from each other.
3. The distance between the protrusions of the femurs in the area of ​​​​the transition of their upper part 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 tool (tazomer), 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 tissues does not affect the result of the study. The parameters of the pelvis are evaluated by bone protrusions, and they do not shift anywhere when losing weight or, on the contrary, gaining weight. The dimensions of the pelvis remain unchanged after a woman reaches the age when bone growth stops.

For the diagnosis of narrowing of the pelvis, two more conjugates are important - true (obstetric) and diagonal. However, it is not possible to directly measure them; one can judge their size only indirectly. 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 value 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.

An anatomically narrow pelvis should be spoken of when at least one of the parameters is smaller than the normal size of the pelvis. The degrees of narrowing are distinguished when the true conjugate is less than the norm:

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

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

A clinically narrow pelvis is a situation where the parameters of the fetal head do not match the parameters of the mother's pelvis. Moreover, all sizes of the latter can be within the normal range (that is, from the point of view of anatomy, this pelvis is not always narrow). There may also be a reverse situation, when an anatomically narrow pelvis fully corresponds to the configuration of the fetal head (for example, if the child is not large), and in this case there is no question of the diagnosis of a clinically narrow pelvis.

The main reasons for this condition:

1. On the mother's side: anatomically small pelvis, irregular shape of the pelvis (for example, deformity after injury).
2. On the part of the fetus: hydrocephalus, large size, tilting of the head when the fetus enters the small pelvis.

Depending on how pronounced the difference between the parameters of the mother's pelvis and the fetal head, there are three degrees of a clinically narrow pelvis:

1. Relative inconsistency. In this case, independent childbirth is possible, but the doctor must be ready to make a decision on surgical intervention in a timely manner.
2. Significant discrepancy.
3. Absolute mismatch.

Childbirth with a clinically narrow pelvis

The second and third degrees are indications for surgical intervention. Independent childbirth in this situation is impossible. The fetus can only be removed by performing a caesarean section.

With a relative discrepancy, childbirth in a natural way is permissible. However, one should be aware of the danger of changing the situation for the worse. The doctor should take the question of the severity of the discrepancy even during the period of contractions in order to determine in a timely manner the further tactics. Delayed diagnosis of conditions when delivery should only be performed surgically can lead to serious difficulties in removing the fetal head. With 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 when performing a caesarean section. In such cases, childbirth has to end with a fruit-destroying operation.

Summing up

It is necessary to know the size of the pelvis. This is necessary in order to promptly suspect such pathological conditions as an anatomically and clinically narrow pelvis. The reduction in normal size can be of varying degrees of severity. In some cases, even independent childbirth is possible, in other situations it becomes necessary to perform a caesarean section.

A 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, but the possibility of 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). Therefore, timely diagnosis and a quick decision on further tactics are so important.

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Dimensions of the entrance of the pelvis.

The bony ring of the entrance of a normal pelvis in an adult woman has the shape of a transversely lying oval. In this oval, dimensions are distinguished that go in three directions.
The direct size of the entrance (Fig. 87) - the distance from the middle of the upper edge of the symphysis (on its back surface) to the protruding point of the cape of the sacrum - is 11 cm; this size is called the true conjugate (conjugata) 1.
In obstetrics, two true conjugates are distinguished (Fig. 96). The conjugate just discussed is the anatomical true conjugate; another conjugate passes to the same point of the cape of the sacrum, but not from the upper edge of the symphysis, but slightly lower, from the tubercle on the inner surface of the symphysis - this is an obstetric true conjugate; it is slightly (0.2 - 0.3 cm) shorter than the anatomical one.
The transverse size of the entrance - the distance between the most distant points of the nameless lines - is 13 cm (Fig. 87).
The oblique dimensions of the entrance go from the upper edge of the sacroiliac joint on the right and left to the iliac-pubic tubercle of the opposite side; the oblique size of the entrance is 12 cm.
The conjugate is the shortest dimension of the ellipse.

There are right and left oblique dimensions (Fig. 87); the right one goes from the right sacroiliac joint to the left iliac-pubic tubercle; left oblique size - from the left sacroiliac joint to the right iliac-pubic tubercle. Thus, the directions of oblique dimensions are determined by the backsight from which they start.
It is extremely important to be well versed in this, since these directions are used to determine the position in the pelvis of the presenting part of the fetus.
In the cavity of the small pelvis, the sizes of the wide and narrow parts of it are separately distinguished.
Dimensions of the upper, or wide, part of the pelvic cavity.
The direct size goes from the middle of the posterior surface of the symphysis to the junction of the II sacral vertebra with the III sacral vertebra; it is equal to 12.5 cm.
The transverse dimension passes between the inner surfaces of the bottom of the acetabulum; it is equal to 12.5 cm.
The oblique dimensions of the wide part of the pelvic cavity are the distance from the upper edge of the large ischial notch (incisura ischiadica major) of one side to the upper edge of the obturator foramen (foramen obturatorium) of the other side. Each of these dimensions is 13 cm.
Dimensions of the lower, or narrow, part of the pelvic cavity. Direct size - from the lower edge of the symphysis to the top of the sacrum; it is 11.5 cm.
Transverse size - the distance between the ischial networks; it is equal to 10.5 cm.
This part of the pelvic cavity has the shape of an oval, slightly elongated in the anterior-posterior direction, approaching the standing oval.
The dimensions of the outlet of the pelvis. The direct size (Fig. 88) - the distance from the lower edge of the symphysis to the top of the coccyx - is 9 -9.5 cm. During delivery by pressure of the incoming presenting part of the fetus, the tip of the coccyx folds back by 1 - 1.5 cm, which is why the direct exit size can increase up to 11 cm.
The transverse size of the outlet (Fig. 88) - the distance between the inner sides of the ischial tubercles - is 10.5 cm; the exit of the pelvis has the shape of a standing oval.

Pelvis	Dimensions in cm			Shape (schematically)
	transverse / oblique
Entrance.................................. Cavity:				transverse oval
the plane of the wide part.				Obliquely lying oval Oval approaching a straight position
plane of the narrow part
Exit............................. .				straight oval

Thus, at the entrance of the pelvis, the largest size is transverse; in the cavity - oblique, in the exit - straight size. If you look into the pelvic canal from above, comparing the size and shape of all parts of the small pelvis, we will see that the lumen along its entire length is schematically represented as follows: at the entrance it looks like a transversely lying oval; descending lower, the oval gradually assumes a slightly oblique position; descending even lower, it gradually turns and in the lowest part of the lumen of the pelvic canal, at the exit of the pelvis, takes the position of a standing oval.

Rice. 88. Exit of the pelvis and its dimensions (straight and transverse).
This shape of the individual parts of the pelvic cavity to some extent explains the different position of the presenting part of the fetus in different parts of the pelvic canal. We will return to this when studying the mechanism of childbirth.
Determining the true conjugate from the outer conjugate. To calculate the true conjugate from the outer conjugate, 9 cm is subtracted from the length of the outer conjugate. So, with an outer conjugate equal to 20 cm, the true conjugate is determined at 11 cm. It is clear that this calculation is approximate, since there are a number of points that make it difficult to accurately calculate, as, for example, different thicknesses of soft tissues and the bones themselves.
Determination of the true conjugate by the diagonal conjugate. More precisely, you can determine the length of the true conjugate by the diagonal conjugate (conjugata diagonalis). To determine the diagonal conjugate, i.e., the distance from the lower edge of the symphysis to the prominent point of the promontory of the sacrum, it is necessary to perform a vaginal examination, observing the rules of asepsis and antisepsis (see Chapter VIII).
With the ends of the fingers, they first feel the anterior wall of the pelvis, reveal the structure of the posterior surface of the symphysis, establish whether there are bone protrusions (exostoses) that reduce the size of the pelvis, determine the approximate height of the symphysis, then feel the side walls of the pelvis and also reveal whether there are any deformations here.

Rice. 89. Diagonal conjugate measurement (first moment).

Rice. 90. Diagonal conjugate measurement (second moment).
Along the way, they find out the condition of the vagina (narrow, short) - all this is important for taking into account the nature of the course of the upcoming birth. Finally, along the back wall of the vagina, along the sacral cavity, they move up and try to reach the cape of the sacrum. In a normal pelvis, the promontory can only be reached if the examining midwife has long fingers. Usually, with the average length of the fingers of the examiner's hand, if the cape is not reached, the diagonal conjugate is considered normal, that is, equal to 12.5 cm.

The diagonal conjugate can, to a certain extent, be considered as the hypotenuse of a right triangle, in which one leg is the symphysis, the other is the true conjugate (Fig. 96). Having the opportunity to measure the diagonal conjugate and the height of the symphysis (Fig. 94), that is, knowing the length of the hypotenuse and one of the legs, we can calculate the length of the other leg.

Rice. 91. Measurement of the direct size of the exit of the pelvis.
If the cape is reached, then, resting against it with the end of the middle finger of the investigating hand, with the end of the index finger of the other hand (Fig. 89), they mark on the investigating hand the place where it touches the lower edge of the symphysis; the marking index finger is not taken away, but the fingers are removed from the vagina along with the mark. Then they ask the nanny or, in extreme cases, the pregnant woman to measure with a centimeter tape, or better with a tazomer (Fig. 90), the distance from the mark to the end of the middle finger - this will be the length of the diagonal conjugate. To determine the size of a true conjugate, an average of 1.5 to 2 cm is subtracted from the length of the diagonal conjugate due to the difference in length between the two conjugates.
Determining the size of the exit of the pelvis. To determine the size of this part of the pelvis, the woman is placed in a position on her back with her hips pressed against her stomach.
The direct size of the exit of the pelvis is measured from the lower edge of the symphysis to the top of the coccyx (Fig. 91).
The transverse size of the outlet is the distance between the ischial tubercles. First, the ischial tubercles are felt with their fingers, and the buttons of a special tazomer are pressed tightly against the inner surfaces of these tubercles, or this distance is measured with a centimeter tape (Fig. 92). 1-1.5 cm is added to the size obtained in this way, depending on the thickness of the subcutaneous fat layer.

Rice. 92. Measurement of the transverse size of the exit of the pelvis.
The size of the exit of the pelvis can also be judged by the size of the pubic angle. In a normal female pelvis, this angle is obtuse; the smaller the pubic angle, the closer the ischial tubercles are located to each other. Roughly it can be measured, as shown in Fig. 93.

Oblique dimensions of the pelvis

The asymmetry of the pelvis is determined based on the measurement of the oblique dimensions of the pelvis. To do this, compare the distances between the following points:

1. from the middle of the symphysis to the posterior superior iliac spines on the right and left (for a normal pelvis 17 cm);

Rice. 93. Measurement of the magnitude of the pubic angle

1. from the anterior-superior spine of one side to the postero-superior spine of the opposite side and vice versa (for a normal pelvis 21 cm);

3) from the spinous process of the V lumbar vertebra to the anterior superior spine of the right and left iliac bones (for a normal pelvis 18 cm).

Rice. 94. Determining the height of the symphysis
In a symmetrical pelvis, these paired sizes are the same; if one is larger and the other is smaller, then the pelvis is asymmetrical, oblique. The difference in the magnitude of the oblique dimensions already determines the degree of this distortion. The asymmetry of the pelvis can be judged to some extent by the shape of the lumbar rhombus (p. 357).

Measurement of the height of the symphysis

If, for example, when measuring the diagonal conjugate, the latter turns out to be shorter than usual - let's say that it is not 12.5, but 12 cm, then in order to more accurately determine the length of the true conjugate, it is important to know the height of the symphysis in this woman. If it turns out that the symphysis
below 4 cm, approximately 3.5 cm, then the true conjugate may be normal even with a diagonal conjugate equal to 12 cm. Thus, depending on the height of the symphysis, the difference in length between the true and diagonal conjugate fluctuates. To measure the height of the symphysis, a bent index finger is drawn along the back surface of the symphysis and pressed tightly to it with the palmar surface (Fig. 94). Having reached the upper edge of the symphysis with the end of the investigating finger, with the index finger of the other hand mark the point of contact with the lower edge of the symphysis and then measure the distance between the end of the investigating finger and the mark on it - this will be the height of the symphysis; on average, a height of 4 cm is considered normal.
For example, if the height of the symphysis is more than 4 cm, to determine the true conjugate, not 1.5, but 2 cm should be subtracted from the length of the diagonal conjugate.