WOMEN'S THAI. Its size and bones. Normal form of the female pelvis.

FEMALE THAZ from obstetric point of view.

The pelvis consists of two pelvic, sacral and coccygeal bones, which are firmly connected through cartilaginous layers and bonds.

The pelvic bone is formed from the fusion of three bones: longitudinal, ischial and pubic. They are connected in the area of ​​the acetabulum.

The sacral bone consists of 5-6 fixedly connected vertebrae, which merge into one bone.

The osseous bone consists of 4-5 undeveloped vertebrae.

Bone pelvis in the upper section is opened forward. This part is called a large pelvis. Lower part Is a closed bone formation - a small pelvis. The border between the large and small pelvis is the terminal (nameless) line: in front - the upper edge of the symphysis and pubic bones, from the sides - arched lines of the ileum bones, behind - sacral speech. The plane between the large and small pelvis is the entrance to the small pelvis. The large pelvis is much wider than the small one, it is limited from the sides by the wings of the iliac bones, behind - the last lumbar vertebrae, in front - the lower part of the anterior abdominal wall.

All women undergo a measurement of the large pelvis. Between the size of the large and small pelvis there is a relationship. By measuring a large pelvis, we can draw conclusions about the size of a small one.

The normal size of the female pelvis:



  • distantia spinarum - distance between the anterior superior bones of the longitudinal bone - 25-26 cm;

  • distantia cristarum - the distance between the distant points of the crests of the iliac bones - 28-29 cm;

  • conjugata externa - (outer conjugate) - distance from the middle of the upper edge of the symphysis to the upper corner of the Michaelis rhombus (measurements are made in the position of the woman lying on its side) - 20-21 cm.


  • Rhombus Michaelis - this is an extension of the deepening in the sacral region, the limits of which are: from above - the fossa under the spinous process of the fifth lumbar vertebra (over the curve of the fovea), from below - the points corresponding to the posterior superiority of the iliac bones. The average length of the diamond is 11cm, and the diameter is 10cm.

    The diagonal conjugate is - The distance from the lower edge of the symphysis to the most prominent point of the cape of the sacrum is determined by vaginal examination. With the normal size of the pelvis, it is 12.5-13 cm.

    The size of the true conjugate (the direct size of the entrance to the small pelvis) is determined by subtracting 9cm from the length of the outer conjugate or subtracting 1.5-2cm from the length of the diagonal conjugate (depending on the Solov'ev index).

    The index of Solovyov - circumference of the wrist-carpal joint, divided by 10. The index allows you to have an idea of ​​the thickness of the bones of a woman. The thinner the bone (index = 1.4-1.6), the greater the capacity of the small pelvis. In these cases, the diagonal conjugate is subtracted 1.5 cm and the length of the true conjugate is obtained. With the Solov'ev index

    I, 7-1.8 - take away 2cm.

    The angle of the pelvis is - the angle between the plane of entry into the small pelvis and the horizon is 55-60 °. Deviations in one direction or another can adversely affect the course of labor.

    The height of the symphysis is normally 4 cm and is measured by the index finger in vaginal examination.

    The pubic angle - at normal pelvic dimensions is 90-100 °.

    Small basin Is the osseous part of the birth canal. The posterior wall of the small pelvis consists of the sacrum and coccyx, the lateral - formed of the ischium bone, the anterior - by pubic bone and symphysis. The small pelvis has the following sections: entrance, cavity and outlet.

    In the pelvic cavity, the wide and narrow parts are distinguished. In this connection, four planes of the small pelvis are determined:



    1 - the plane of entry into the small pelvis.

    2 - the plane of the broad part of the pelvic cavity.

    3 - the plane of the narrow part of the pelvic cavity.

    4 - exit plane from the pelvis.

    The plane of the entrance to the small pelvis passes through the upper inner edge of the pubic arch, the nameless lines and the tip of the cape. In the input plane, the following dimensions are distinguished:

  • The direct dimension is the distance from the sacral presentation to the point most prominent on the upper inner surface of the symphysis is the obstetric, or true conjugate, equal to 11cm.

  • The transverse dimension is the distance between the distant points of the arcuate lines, which is 13-13.5 cm.

  • Two oblique dimensions - from the ilio-sacral connection from one side to the iliac-pubic tubercle from the opposite side of the pelvis. They are 12-12.5 cm.


  • The plane of the wide part of the cavity of the small pelvis passes through the middle of the inner surface of the lumbar arch, laterally through the middle of the acetabulum and from behind - through the connection between the II and III sacral vertebrae.

    In the plane of the wide part of the small pelvis, is isolated.



  • Straight size - from the middle of the inner surface of the pubic arch to the connection between the II and III sacral vertebrae. It is 12.5 cm.

  • The transverse dimension passes between the centers of the swirls of the basins. It is 12.5 cm.


  • The plane of the narrow part through the lower edge of the pinnate joint, along the sides - through the gluteus awns, from the rear -

    through the sacrococcygeal joint.

    In the plane of the narrow part is distinguished:

    1. Direct size - from the lower edge of the symphysis to the sacrococcygeal joint. It is equal to II, 5cm.

    2. The transverse dimension between the distant points of the inner surface of the sciatic ligaments. It is equal to 10.5 cm.

    The exit plane from the small pelvis runs from the front through the lower edge of the symphysis, from the sides - through the tops of the gluteal tubercles, from behind - through the crown of the coccyx.

    In the plane of exit from the small pelvis, the following are isolated:

    1. Straight size - from the top of the coccyx to the lower edge of the symphysis. It is 9.5 cm, and when the fetus passes through the small pelvis it increases by 1.5-2 cm due to the deflection of the tip of the coccyx of the presenting part of the fetus.

    2. Transverse dimension - between distant points of internal surfaces of sciatic tubercles; it is 11cm.

    The line connecting the middle of the direct dimensions of all the planes of the pelvis is called the leading axis of the pelvis, and has the form of a concave forward line. It is along this line that the leading point passes through the generic canal.

    The main differences of the female pelvis from the male:

  • Bones of the female pelvis are comparatively thin and smooth;

  • Female pelvis is relatively wider, lower and larger in volume;

  • The wings of the iliac bones in women are more developed, so the transverse dimensions of the female pelvis are larger than the male ones;

  • The entrance to the small pelvis of a woman has a cross-oval shape, and in men - the shape of a card heart;

  • The entrance to the small pelvis is greater in women and the pelvic cavity does not narrow downwards like a funnel-like one in men;

  • The long angle in women is stupid (90-100 °), while in men it is acute (70-75 °);

  • The angle of pelvic incline in women is more (55-60 °) than in men (45 °).