The conjugate is true, external, diagonal. Dimensions of the small pelvis of a woman

Measurement of the pelvis is mandatory for all pregnant women. This is a fast, painless and absolutely harmless procedure, the fulfillment of which is an indispensable condition for the registration of a pregnant card at the first referral of a woman to a gynecologist. Focusing on the size of the pelvis, you can plan the management of childbirth: by natural route or by surgical method (caesarean section). Timely chosen tactics allows to avoid many complications, which threaten the life of a woman and her baby. Properly planned births - 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 cavity of the small pelvis on the inner surface of the symphysis. Normally, this distance is 11 cm.

What is a small pelvis?

The pelvis as anatomical formation is represented by two pelvic bones and a distal spine (sacrum and coccyx). In obstetrics, only the part that is called a small pelvis is important. This space is limited by the lower parts of the pelvic bones, 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 dimensions, important in obstetric practice.

Parameters of the entrance to the small pelvis

1. The size is straight. This indicator has other names - conjugate obstetric and conjugate true. It is equal to 110 mm.
2. The size is transverse. It is equal to 130-135 mm.
3. Dimensions are oblique. They are 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. Is equal to 125 mm.
2. The size is transverse. Is equal to 125 mm.

Parameters of the narrow part of the small pelvis

1. The size is straight. Raven is 110-115 mm.
2. The size is transverse. It is equal 105 mm.

Parameters of the exit from the small pelvis

1. The size is straight. During childbirth can increase, since the head of the fetus moving along the birth canvasses bends the coccyx backward. It is 95-115 mm.
2. The size is transverse. It is equal to 110 mm.

Measuring the pelvis of a pregnant woman

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

1. Distance between the aorta of iliac bones located at the anterior edge of the crest.
2. Distance between the points of the crests of the iliac bones, distant from each other to the maximum distance.
3. Distance between the projections of the femurs in the area of transition of their upper part into the cervix.
4. External conjugate (distance from pubic symphysis to lumbosacral cavity).

Thus, the normal size of the pelvis is equal to 250-260, 280-290, 300-320 and 200-210 millimeters, respectively. The elucidation of these parameters is mandatory when the pregnant woman is registered. Measurement is carried out by a special instrument (tasometer), which, by the way, can also be used for measurements of the head of a born 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 on the bony protuberances, and they do not move anywhere with weight loss or, on the contrary, gain in weight. The size of the pelvis remains unchanged after the woman reaches the age when the growth of bones ceases.

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

The true conjugate is determined by 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 a narrow pelvis - anatomical and clinical. These concepts, although not identical, are closely related.

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

• On 15-20 mm.
• 20-35 mm.
• 35-45 mm.
• More than 45 mm.

The last two degrees indicate the need for surgical intervention. Conjugate true 1-2 degree allows the possibility to continue childbirth in a natural way, provided that there is no threat of the appearance 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. In this case, all the dimensions of the latter can be within the norm (that is, from the point of view of anatomy this pelvis is not always narrow). There may be a reverse situation, when an anatomically narrow pelvis completely corresponds to the configuration of the fetal head (for example, if the child is not large), and there is no question of a clinically narrow pelvis in this case.

Clinically narrow pelvis

The main causes of this condition:

1. From the mother's side: anatomically small pelvic dimensions, irregular pelvic shape (for example, deformation after trauma).
2. On the part of the fetus: hydrocephalus, a large size, a pregnant pregnancy, tipping over the head when the fetus enters the small pelvis.

Depending on how pronounced the difference between the parameters of the pelvis of the mother and the head of the fetus, distinguish three degrees of clinically narrow pelvis:

1. Relative discrepancy. In this case, independent births are possible, but the physician should be ready to make a timely decision on surgical intervention.
2. Significant discrepancy.
3. Absolute discrepancy.

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 be removed only by performing cesarean section. With relative inconsistency, births are naturally tolerated. However, one should remember about the danger of changing the situation for the worse. The doctor should take into consideration the severity of the discrepancy during the period of labor, in order to determine in due time the further tactics. A belated diagnosis of conditions, when the delivery should be performed only surgically, can lead to serious difficulties with the removal of the fetal head. At the expressed discrepancy the last will be beaten up in a cavity of a basin by a cutting uterus that will lead to a serious trauma of a head and destruction. In advanced cases, it is impossible to extract the fetus alive from the pelvic cavity, even when performing cesarean section. In such cases, the labor must be terminated with a fruit-destroying operation.

Let's sum up the results

Know the size of the pelvis is necessary. This is necessary in order to timely suspect such pathological conditions as an anatomically and clinically narrow pelvis. Reduction in normal sizes can be of different degrees of severity. In some cases, even independent births are possible, in other situations, it becomes necessary to perform a caesarean section operation. Clinically narrow pelvis - a very insidious state. It is not always combined with the concept of an anatomically narrow pelvis. The latter may have normal parameters, but the possibility of a discrepancy in the size of the head of the pelvis still exists. The emergence of such a situation during childbirth can cause dangerous complications (first of all the fetus will suffer). Therefore, timely diagnostics and prompt decision-making on further tactics are so important.