Anatomically narrow is the pelvis, one of the sizes to-rogo compared with the norm is reduced by 2 cm or more (see Taz female). According to the shape and degree of narrowing, they distinguish an evenly narrowed, simple, flat, flat-rachitic and common narrowed pelvis. The degree of narrowing is judged by the magnitude of the true conjugates.
There are 4 degrees of pelvic contraction: 1st degree - true conjugate is less than 11 cm and not less than 9 cm (with this degree of pelvic narrowing, childbirth in most cases ends spontaneously, but there are difficulties with the conjugate approaching 9 cm); 2nd degree - true conjugate from 9 to 7.5 cm (delivery of a full-term fetus is possible with good labor, the correct configuration and small head sizes); 3rd degree - true conjugate 7.5-6.5 cm; The 4th degree is an absolutely narrow pelvis, a true conjugate of 6.5 cm and less (at the 3rd and 4th degrees, delivery through natural birth canal is impossible, the only method of delivery is caesarean section).
When determining the degree of contraction of the pelvis should take into account the thickness of the bones, which is determined by the wrist index.A common-even constriction is the pelvis, in which all sizes are uniformly reduced; occurs preim. in women of small stature, the right physique. If such a pelvis interferes with the birth of the head, the mechanism of labor is different from normal in that the head, entering the entrance to the pelvis in one of the oblique dimensions, bends as much as possible; due to maximal small spring, bending of the head approaches the wire axis of the pelvis. The second feature of the labor mechanism is that the arrow-shaped suture is always located in one of the oblique dimensions of the entrance. Passing through the pelvic outlet, the region of the suboccipital fossa cannot come close to the symphysis due to the narrowness of the pubic angle. Therefore, the head strongly deviates towards the perineum, its tissues stretch more strongly, and if it does not provide the necessary assistance, a deep rupture of the perineum occurs. The head of the newborn is stretched to the side of the neck (expressed dolichocephalic configuration), in the area of the small fontanelis means a generic tumor. The pelvis is simple and flat, and the sacrum is close to the symphysis; in connection with this reduced all the direct dimensions of the pelvis.Characteristic features of the mechanism of labor: the head enters the entrance to the pelvis with an arrow-shaped suture in transverse size; there is a moderate extension of the head (small and large fontanelles are located on the same level); Asynclitich is observed. insertion of the head (front, ambient). More favorable for childbirth front asynclitism.
Often the head passes all the planes of the small pelvis arrow-shaped suture in transverse size. This state is called. medium and low transverse standing of the head; often, it dictates the need to extract the head by applying an atypical forceps or performing a craniotomy operation. Ploskarakhitichesky pelvis is found in women who have rickets, and is characterized by several features. The wings of the iliac bones are deployed; the distance between the anteropal spines of the iliac bones is increased, the distance between the iliac bones (distantia spinarum) in its size approaches the distance between the crests (distantia cristarum). The sacrum is flattened and deflected posteriorly, and the tailbone is turned anteriorly. Sometimes, on the front surface of the flat sacrum, an additional (false) cape is formed as a result of cartilage ossification between the I and II sacral vertebrae. An additional cape may present a difficulty in moving the prelying part.The size of the exit of the small pelvis increased. The mechanism of childbirth at ploskorahitich. The pelvis is initially characterized by the same features as with a simple flat pelvis. After the head passes through the narrowed entrance of the pelvis, the expulsion of the fetus is completed very quickly. A generic tumor is usually located on the pre-parietal parietal bone of the born head.
A common flat is the pelvis, in which all the dimensions are reduced, but the direct dimensions (especially the direct size of the entrance to the pelvis) are shortened the most; usually occurs when the combination of two pathological. processes: infantilism and rickets, transferred in childhood. The delivery proceeds according to the type characteristic of the common-contracted or flat pelvis.