Measurement of the pelvis 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 the size of the pelvis, 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. A properly planned birth is a guarantee that the birth of a child will be easy and safe.
True conjugate is the shortest distance between the cape and the most protruding point in the pelvic cavity on the inner surface of the symphysis. Normally, this distance is 11 cm.
What is the pelvis?
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 a space bounded by the lower parts of the pelvic bones, the sacrum and the coccyx. It contains the followingorgans: bladder, uterus and rectum. In its structure, four main planes are distinguished. Each of them has several sizes that are important in obstetric practice.
Pelvis entry parameters
- Size straight. This indicator has other names - obstetric conjugate and true conjugate. Equals 110 mm.
- The size is transverse. Equals 130-135 mm.
- The sizes are oblique. Equal 120-125 mm.
- Diagonal conjugate. Equal to 130 mm.
Parameters of the wide part of the small pelvis
- Size straight. Equals 125 mm.
- The size is transverse. Equals 125 mm.
Parameters of the narrow part of the pelvis
- Size straight. Equals 110-115 mm.
- The size is transverse. Equals 105 mm.
Pelvis exit parameters
- Size straight. During childbirth, it can increase, as the head of the fetus moving along the birth canal bends the coccyx backwards. Is 95-115mm.
- The size is transverse. Equals 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:
- The distance between the iliac spines located at the anterior edge of the crest.
- The distance between the points of the iliac crests, distant from each otherfriend to the maximum distance.
- The distance between the protrusions of the femurs in the area of transition of their upper part to the neck.
- External conjugate (distance from pubic symphysis to lumbosacral cavity).
Thus, the normal dimensions of the pelvis are 250-260, 280-290, 300-320 and 200-210 millimeters respectively.
The clarification of these parameters is mandatory when registering a pregnant woman. The measurement is carried out with a special tool (pelvis 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 evaluated by bone 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.
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.
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 notidentical, but closely related.
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 45mm.
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 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 the 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 a clinically narrow pelvis.
Clinically narrow pelvis
Main causes of this condition:
- Maternal side: anatomically small pelvis, malformation of the pelvis (e.g. deformity after injury).
- From the side of the fetus: hydrocephalus, large size, post-term pregnancy, tilting of 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, there are three degrees clinicallynarrow pelvis:
- Relative mismatch. In this case, independent childbirth is possible, but the doctor must be ready to make a decision on surgical intervention in a timely manner.
- Significant mismatch.
- A total mismatch.
Childbirth with a clinically narrow pelvis
Second and third degrees are indications for surgery. Independent childbirth in this situation is impossible. The fetus can only be delivered by caesarean section.
With relative discrepancy, natural birth is acceptable. 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 where 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.
Summarize
Know the size of the pelvis is necessary. 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.expressiveness. 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.
