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

Pelvic measurement is mandatory for all pregnant women. It 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 means or by a 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 an 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 of the straight. This indicator has other names - conjugate obstetric and conjugate true. It is equal to 110 mm.
2. The size is transverse. Is equal to 130-135 mm.
3. Dimensions are skew. They are equal to 120-125 mm.
4. Diagonal conjugate. Equal to 130 mm.

Parameters of the wide part of the small pelvis

1. Size straight. Is equal to 125 mm.
2. Size is transverse. Is equal to 125 mm.

Parameters of a narrow part of a small pelvis

1. The size of a straight line. It is equal to 110-115 mm.
2. The size is transverse. It is equal 105 mm.

Parameters of the exit from the small pelvis

1. Size straight. During childbirth may increase, as the head of the fetus moving along the birth canal 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

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 obstetric practice, the most important parameters are as follows:

1. The distance between the iliac spine located at the anterior edge of the crest.
2. The distance between the points of the crests of the iliac bones, distant from each other for the maximum distance.
3. Distance between the projections of the femurs in the area of ​​transition of their upper part into the cervix.
4. Outer 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. It is necessary to find out these parameters when registering a pregnant woman. Measurement is carried out by a special instrument( tasometer), which, by the way, can also be used for measuring 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 bone growth stops.

Two more conjugates are important for diagnosis of pelvic narrowing - 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 conjugate obstetrics.

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:

• by 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 diagnosis in this case.

Clinically narrow basin

The main causes of this condition:

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

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

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 inconsistency.
3. Absolute discrepancy.

Births in the clinically narrow pelvis

The second and third degrees are indications for surgery. Independent childbirth in this situation is impossible. The fetus can be removed only by performing cesarean section. With relative mismatch, 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 delivering only surgically, can lead to serious difficulties with the removal of the fetal head. If expressed inconsistency, the latter will be pumped into the pelvic cavity by a shrinking uterus, which will lead to severe head trauma and death. 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 completed with a fruit-destroying operation.

Summing up

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. The decrease in normal size can be of different degrees of severity. In some cases even independent births are possible, in other situations there is a need 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 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.