Thus, pelvis appears as if in the form of a canal, definitely curved in the anterior direction. But it only seems so. In fact, as research has shown, bony pelvis not bent anteriorly. When the fetus passes with its head through the birth canal, its head circumference passes through several planes until it reaches the bottom of the pelvic cavity. The planes through which the fruit passes with its head were studied by the scientist Goji and named them as parallel planes. When examining a woman, they are easily identified by well-identified anatomical points.
Among the parallel planes, there are four planes that are essential for understanding obstetrics. These planes are at an equal distance from each other, approximately 3-4 cm.
The topmost and first plane is located at the level of the terminal line and passes through it (linea terminalis or innominata), as a result of which it was called the terminal plane.
Second plane, is located at some distance from the first and is parallel to it. The second plane of the pelvis passes at the level of the pubic symphysis and intersects it at the level of the lower edge. Given the location of the plane, it was called the inferior pubic parallel plane. It is also called the main plane, because the head, having passed this plane, usually no longer encounters obstacles on further path(passed a solid bone ring).
Third plane of the pelvis, is parallel to all the planes described above and passes through the pelvis at the level of the spinae ossis ischii of the pelvis. As a result, the third plane of the pelvis was called the spinal plane.
Finally, fourth plane, parallel to the third, represents the pelvic floor, its diaphragma (diaphragma) and almost coincides with the direction of the coccyx. This plane is usually called the output plane.
The head goes into the pelvis from the entrance to its bottom (almost do perpendicular to the lily, which intersects all four parallel planes.
When the head wire point j will descend to the exit plane, the head turns anteriorly, towards the exit. Thus, the pelvic axis is a line in the form of an arc connecting the middle, of all straight sizes, reminiscent, in the words of A.P. Gubarev, of a fish hook: in the upper parts of the pelvis, the direction of the genital canal (pelvic axis) goes in a straight line from top to bottom, making a sharp anterior turn at the bottom of the pelvis, approximately at the level of the spinal plane (knee of the birth canal).
Connection of the pelvic bones.
Pelvic bones(outdated name - nameless), the sacrum and coccyx are connected to each other by the following strong joints.
1. symphysis pubis(symphysis) - fusion of the pubic bones through a fibrocartilaginous layer with the formation of a narrow articular cavity in the center. The pubic symphysis is strengthened by powerful, strong ligaments. The symphysis as a semi-joint (hemiarthrosis) has an extremely limited range of movements. Only during pregnancy, due to edematous impregnation and loosening of tissues, small movements (up to 10 mm) of the articular ends, pubic bones up and down, like the keys of a piano, are possible, especially in young multiparous women. Such mobility is of some importance in the management of labor with difficult insertion of the head and when surgical interventions. In some cases, greater mobility in the symphysis pubis causes some pain and awkwardness when walking and standing during pregnancy.
2. Sacroiliac joint(articulatio sacroiliaca) - connection of the sacrum with both iliac bones. Thus, the joint is a pair, built in the same type as the symphysis, and also has strong ligaments. The joint is a typical amphiarthrosis, its active mobility is zero, its passive mobility is minimal (Krukenberg) - only light sliding movements are possible.
3. Sacrococcygeal joint(articulatio sacro-coccygea) - connection between the distal surface of the coccyx. The articulation is supported laterally, as well as anteriorly and posteriorly, by accessory ligaments. It is so mobile that the coccygeal bone can freely bend backward, which is actually what happens during childbirth. The softening of articular cartilage during pregnancy increases joint mobility. With age (after 35-40 years) in women, due to ossification of the cartilage, the mobility of the joint decreases, as a result of which during childbirth, with a sharp deviation of the coccyx posteriorly, its dislocation and even fracture can occur.
SMALL PELVIS Planes and dimensions of the small pelvis. The pelvis is the bony part of the birth canal. Back wall The small pelvis consists of the sacrum and coccyx, the lateral ones are formed by the ischial bones, the anterior one by the pubic bones and the symphysis. The posterior wall of the pelvis is 3 times longer than the anterior one. Upper section The pelvis is a continuous, inflexible ring of bone. In the lower section, the walls of the small pelvis are not solid; they contain obturator foramina and sciatic notches, bounded by two pairs of ligaments (sacrospinous and sacrotuberous). In the small pelvis there are the following sections: inlet, cavity and outlet. In the pelvic cavity there are a wide and a narrow part. In accordance with this, four planes of the pelvis are considered: I – the plane of the entrance to the pelvis, II – the plane of the wide part of the pelvic cavity, III – the plane of the narrow part of the pelvic cavity, IV – the plane of the exit of the pelvis.
I. The plane of entrance to the small pelvis has the following boundaries: in front - the upper edge of the symphysis and the upper inner edge of the pubic bones, on the sides - innominate lines, behind - the sacral promontory. The entrance plane has the shape of a kidney or a transverse oval with a notch corresponding to the sacral promontory. At the entrance to the pelvis there are three sizes: straight, transverse and two oblique. Straight size - the distance from the sacral promontory to the most prominent point on the inner surface of the pubic symphysis. This size is called the obstetric, or true, conjugate (conjugata vera). There is also an anatomical conjugate - the distance from the promontory to the middle of the upper inner edge of the symphysis; the anatomical conjugate is slightly (0.3-0.5 cm) larger than the obstetric conjugate. The obstetric or true conjugate is 11 cm. The transverse size is the distance between the most distant points of the nameless lines. This size is equal to 13-13.5 cm. There are two oblique sizes: right and left, which are equal to 12-12.5 cm. The right oblique size is the distance from the right sacroiliac joint to the left iliopubic tubercle, the left oblique size is from left sacroiliac joint to the right iliopubic tubercle. In order to more easily navigate in the direction of the oblique dimensions of the pelvis in a woman in labor, M.S. Malinovsky and M.G. Kushnir is offered next appointment. The hands of both hands are folded at right angles, with the palms facing upward; the ends of the fingers are brought closer to the outlet of the pelvis of the lying woman. The plane of the left hand will coincide with the left oblique size of the pelvis, the plane of the right hand will coincide with the right.
II. The plane of the wide part of the pelvic cavity has the following boundaries: in front - the middle of the inner surface of the symphysis, on the sides - the middle of the acetabulum, in the back - the junction of the II and III sacral vertebrae. In the wide part of the pelvic cavity, two sizes are distinguished: straight and transverse. Direct size - from the junction of the II and III sacral vertebrae to the middle of the inner surface of the symphysis; equal to 12.5 cm. Transverse size - between the apices of the acetabulum; equal to 12.5 cm. There are no oblique dimensions in the wide part of the pelvic cavity because in this place the pelvis does not form a continuous bone ring. Oblique dimensions in the widest part of the pelvis are conditionally allowed (length 13 cm).
III. The plane of the narrow part of the pelvic cavity is limited in front by the lower edge of the symphysis, on the sides by the spines of the ischial bones, and behind by the sacrococcygeal joint. There are two sizes: straight and transverse. The straight dimension goes from the sacrococcygeal joint to the lower edge of the symphysis (apex of the pubic arch); equal to 11-11.5 cm. The transverse dimension connects the spines of the ischial bones; equal to 10.5 cm.
IV. The plane of exit of the small pelvis has the following boundaries: in front - the lower edge of the symphysis, on the sides - the ischial tuberosities, in the back - the apex of the coccyx. The exit plane of the pelvis consists of two triangular planes, the common base of which is the line connecting the ischial tuberosities. There are two sizes of the pelvic outlet: straight and transverse. The direct size of the pelvic outlet goes from the apex of the coccyx to the lower edge of the symphysis; it is equal to 9.5 cm. When the fetus passes through the small pelvis, the coccyx moves away by 1.5-2 cm and the direct size increases to 11.5 cm. The transverse size of the pelvic outlet connects the internal surfaces of the ischial tuberosities; equal to 11 cm. Thus, at the entrance to the pelvis largest size is transverse. In the wide part of the cavity, the straight and transverse dimensions are equal; the largest size will be the conventionally accepted oblique size. In the narrow part of the cavity and the pelvic outlet, the straight dimensions are larger than the transverse ones. In addition to the above (classical) pelvic cavities, parallel planes of the pelvis (Goji planes) are distinguished. The first (upper) plane passes through the terminal line (I. terminalis innominata) and is therefore called the terminal plane. The second is the main plane, running parallel to the first at the level of the lower edge of the symphysis. It is called the main one because the head, having passed this plane, does not encounter significant obstacles, since it has passed a solid bone ring. The third is the spinal plane, parallel to the first and second, crossing the pelvis in the spina oss area. ischii. The fourth, the exit plane, represents the pelvic floor (its diaphragm) and almost coincides with the direction of the coccyx. Wired axis (line) of the pelvis. All planes (classical) of the pelvis border in front with one or another point of the symphysis, and in the back - with different points of the sacrum or coccyx. The symphysis is much shorter than the sacrum and coccyx, so the planes of the pelvis converge anteriorly and fan out posteriorly. If you connect the middle of the straight dimensions of all the planes of the pelvis, you will get not a straight line, but a concave anterior (towards the symphysis) line. This conditional line, connecting the centers of all direct dimensions of the pelvis, is called the wire axis of the pelvis. The wire axis of the pelvis is initially straight; it bends in the pelvic cavity according to the concavity of the inner surface of the sacrum. Towards wire axis The born fetus passes through the birth canal.
The angle of inclination of the pelvis (the intersection of the plane of its entrance with the plane of the horizon) when a woman is standing can vary depending on the body type and ranges from 45-55°. It can be reduced by forcing a woman lying on her back to strongly pull her thighs towards her stomach, which leads to elevation of the womb. It can be increased by placing a roll-shaped hard pillow under the lower back, which will lead to a downward deviation of the womb. A decrease in the angle of inclination of the pelvis is also achieved if the woman is given a semi-sitting position, squatting.
By puberty healthy woman The pelvis should have a normal shape and size for a woman. To form a correct pelvis it is necessary normal development girls during the prenatal period, prevention of rickets, good physical development and nutrition, natural ultraviolet radiation, injury prevention, normal hormonal and metabolic processes.
The pelvis (pelvis) consists of two pelvic, or nameless, bones, the sacrum (os sacrum) and the coccyx (os coccygis). Each hip bone consists of three fused bones: the ilium (os ilium), the ischium (os ischii) and the pubis (ospubis). The pelvic bones are connected in front by the symphysis. This inactive joint is a semi-joint in which the two pubic bones are connected by cartilage. The sacroiliac joints (almost immobile) connect the lateral surfaces of the sacrum and the ilia. The sacrococcygeal joint is a movable joint in women. The protruding part of the sacrum is called the promontory.
Measuring the size of the pelvis.
To assess pelvic capacity, 3 external dimensions of the pelvis and the distance between the femurs are measured. Measuring the pelvis is called pelvimetry and is carried out using a pelvimeter.
External dimensions of the pelvis:
- Distancia spinarum - interspinous distance - the distance between the anterosuperior spines of the iliac bones (spine - spina), in a normal pelvis is 25-26 cm.
- Distancia cristarum - intercrestal distance - the distance between the most distant points of the iliac crests (crest - crista), normally equals 28-29 cm.
- Distancia trochanterica - intertubercular distance - the distance between the large tuberosities of the trochanters femur(greater tuberosity - trochanter major), normally equals 31 cm.
- Conjugata externa - external conjugate - the distance between the middle of the upper edge of the symphysis and the suprasacral fossa (the depression between the spinous process of the V lumbar and I sacral vertebrae). Normally it is 20-21 cm.
When measuring the first three parameters, the woman lies in a horizontal position on her back with her legs extended, and the pelvic meter buttons are placed on the edges of the size. When measuring the direct size of the wide part of the pelvic cavity. For better identification large skewers the woman is asked to bring her toes together. When measuring the external conjugate, the woman is asked to turn her back to the midwife and bend her lower leg.
Michaelis rhombus
- this is an expansion of the depression in the sacral region, the limits of which are: above - the fossa under the spinous process of the fifth lumbar vertebra (supracrigian fossa), below - the points corresponding to the posterosuperior spine of the iliac bones. The average length of a rhombus is 11 cm, and its diameter is 10 cm.
Diagonal conjugate
– the distance from the lower edge of the symphysis to the most protruding point of the promontory of the sacral bone is determined during vaginal examination. At normal sizes pelvis it is 12.5-13 cm.
The size of the true conjugate (direct size of the entrance to the small pelvis) is determined by subtracting 9 cm from the length of the external conjugate or subtracting 1.5-2 cm from the length of the diagonal conjugate (depending on the Solovyov index).
Solovyov index
- the circumference of the wrist-carpal joint, divided by 10. The index allows you to have an idea of the thickness of a woman’s bones. The thinner the bones (index = 1.4-1.6), the greater the capacity of the small pelvis. In these cases, 1.5 cm is subtracted from the diagonal conjugate to obtain the length of the true conjugate. If the Solovyov index is 1.7-1.8, 2 cm is subtracted.
Pelvic tilt angle
– the angle between the plane of the entrance to the small pelvis and the horizon is 55-60 °. Deviations in one direction or another can negatively affect the course of labor.
The normal height of the symphysis is 4 cm and is measured index finger during vaginal examination. Pubic angle - with normal pelvic sizes is 90-100 °.
Small pelvis
- This is the bony part of the birth canal. The posterior wall of the small pelvis consists of the sacrum and coccyx, the lateral ones are formed by the ischium, and the anterior wall is formed by the pubic bones and the symphysis. The small pelvis has the following sections: inlet, cavity and outlet.
In the pelvic cavity there are wide and narrow parts. In this regard, four planes of the pelvis are determined:
1 – plane of entrance to the small pelvis.
2 – plane of the wide part of the pelvic cavity.
3 – plane of the narrow part of the pelvic cavity.
4 – plane of exit from the pelvis.
The plane of entry into the pelvis passes through the upper inner edge of the pubic arch, the innominate lines and the apex of the promontory. The following dimensions are distinguished in the entrance plane:
- Direct size - the distance from the sacral protrusion to the point that protrudes most on the upper inner surface of the symphysis - this is the obstetric, or true conjugate, equal to 11 cm.
- Transverse size is the distance between the distant points of the arcuate lines, which is 13-13.5 cm.
- Two oblique dimensions - from the iliosacral junction on one side to the iliopubic tubercle on the opposite side of the pelvis. They are 12-12.5 cm.
The plane of the wide part of the pelvic cavity passes through the middle of the inner surface of the pubic arch, on the sides through the middle of the trochanteric cavity and behind - through the connection between the II and III sacral vertebrae.
In the plane of the wide part of the small pelvis there are:
- Direct size - from the middle of the inner surface of the pubic arch to the junction between the II and III sacral vertebrae. It is 12.5 cm.
- The transverse dimension runs between the middles of the acetabulum. It is 12.5 cm.
The plane of the narrow part is through the lower edge of the pubic joint, on the sides - through the gluteal spines, in the back - through the sacrococcygeal joint.
In the plane of the narrow part they are distinguished:
- Straight size - from the lower edge of the symphysis to the sacrococcygeal joint. It is equal to II.5cm.
- The transverse dimension between distant points of the inner surface of the ischial spines. It is equal to 10.5 cm.
The plane of exit from the small pelvis passes in front through the lower edge of the symphysis, from the sides - through the tops of the gluteal tuberosities, and from behind - through the crown of the coccyx.
In the plane of exit from the small pelvis there are:
- Straight size - from the tip of the coccyx to the lower edge of the symphysis. It is equal to 9.5 cm, and when the fetus passes through the pelvis it increases by 1.5-2 cm due to the deviation of the apex of the coccyx of the presenting part of the fetus.
- Transverse size - between distant points of the internal surfaces of the ischial tuberosities; it is equal to 11cm.
The line connecting the midpoints of the straight dimensions of all planes of the pelvis is called the leading axis of the pelvis, and has the shape of a concave line forward. It is along this line that the leading point passes through the birth canal.
By puberty, a healthy woman’s pelvis should have a normal shape and size for a woman. To form a correct pelvis, the girl’s normal development during the prenatal period, prevention of rickets, good physical development and nutrition, natural ultraviolet radiation, injury prevention, normal hormonal and metabolic processes are necessary.The pelvis (pelvis) consists of two pelvic, or nameless, bones, the sacrum (os sacrum) and the coccyx (os coccygis). Each pelvic bone consists of three fused bones: the ilium (os ilium), the ischium (os ischii) and the pubis (ospubis). The pelvic bones are connected in front by the symphysis. This inactive joint is a semi-joint in which the two pubic bones are connected by cartilage. The sacroiliac joints (almost immobile) connect the lateral surfaces of the sacrum and the ilia. The sacrococcygeal joint is a movable joint in women. The protruding part of the sacrum is called the promontory.
In the pelvis there is a distinction between the large and small pelvis.
The large and small pelvis are separated by the innominate line. The differences between the female pelvis and the male pelvis are as follows: in women, the wings of the ilium are more deployed, the small pelvis is more voluminous, which in women has the shape of a cylinder, and in men it has the shape of a cone. The height of the female pelvis is smaller, the bones are thinner.
Measuring the size of the pelvis:
To assess pelvic capacity, 3 external dimensions of the pelvis and the distance between the femurs are measured. Measuring the pelvis is called pelvimetry and is carried out using a pelvimeter.External dimensions of the pelvis:
1. Distancia spinarum - interspinous distance - the distance between the anterosuperior spines of the iliac bones (spine - spina), in a normal pelvis it is 25-26 cm.
2. Distancia cristarum - intercrestal distance - the distance between the most distant points of the iliac crests (crest - crista), normally equals 28-29 cm.
3. Distancia trochanterica - intertubercular distance - the distance between the large tuberosities of the trochanters of the femurs (greater tuberosity - trochanter major), normally equal to 31 cm.
4. Conjugata externa - external conjugate - the distance between the middle of the upper edge of the symphysis and the suprasacral fossa (the depression between the spinous process of the V lumbar and I sacral vertebrae). Normally it is 20-21 cm.
When measuring the first three parameters, the woman lies in a horizontal position on her back with her legs extended, and the pelvic meter buttons are placed on the edges of the size. When measuring the direct size of the wide part of the pelvic cavity, to better identify the greater trochanters, the woman is asked to bring her toes together. When measuring the external conjugate, the woman is asked to turn her back to the midwife and bend her lower leg.
Pelvic planes:
In the pelvic cavity there are conventionally four classical planes.The 1st plane is called the entry plane. It is bounded in front by the upper edge of the symphysis, in the back by the promontory, and on the sides by the innominate line. The direct size of the entrance (between the middle of the upper inner edge of the symphysis and the promontory) coincides with the true conjugata vera. In a normal pelvis, the true conjugate is 11 cm. The transverse dimension of the first plane - the distance between the most distant points of the boundary lines - is 13 cm. Two oblique dimensions, each of which is 12 or 12.5 cm, go from the sacroiliac joint to the opposite iliac joint - pubic tubercle. The plane of entrance to the small pelvis has a transverse oval shape.
The 2nd plane of the pelvis is called the latissimus plane. It passes through the middle of the inner surface of the pubis, sacrum and projection of the acetabulum. This plane has a rounded shape. The straight dimension, equal to 12.5 cm, goes from the middle of the inner surface of the pubic articulation to the articulation of the II and III sacral vertebrae. The transverse dimension connects the middles of the acetabular plates and is also 12.5 cm.
The 3rd plane is called the plane of the narrow part of the small pelvis. It is bounded in front by the lower edge of the symphysis, in the back by the sacrococcygeal joint and on the sides by the ischial spines. The direct dimension of this plane between the lower edge of the symphysis and the sacrococcygeal joint is 11 cm. The transverse dimension, between the inner surfaces of the ischial spines, is 10 cm. This plane has the shape of a longitudinal oval.
The 4th plane is called the exit plane and consists of two planes converging at an angle. In front it is limited by the lower edge of the symphysis (like the 3rd plane), on the sides by the ischial tuberosities, and behind by the edge of the coccyx. The direct size of the exit plane goes from the lower edge of the symphysis to the tip of the coccyx and is equal to 9.5 cm, and in the case of divergence of the coccyx, it increases by 2 cm. The transverse dimension of the exit is limited by the internal surfaces of the ischial tuberosities and is equal to 10.5 cm. When the coccyx diverges, this plane has longitudinal oval shape. The wire line, or pelvic axis, passes through the intersection of the straight and transverse dimensions of all planes.
Internal dimensions of the pelvis:
The internal dimensions of the pelvis can be measured using ultrasound pelvimetry, which is not yet widely used. At vaginal examination the correct development of the pelvis can be assessed. If the promontory is not reached during examination, this is a sign of a capacious pelvis. If the promontory is reached, measure the diagonal conjugate (the distance between the lower outer edge of the symphysis and the promontory), which normally should be at least 12.5-13 cm. The internal dimensions of the pelvis and the degree of narrowing are judged by the true conjugate (direct size of the entrance plane), which in a normal pelvis - at least 11 cm.The true conjugate is calculated using two formulas:
The true conjugate is equal to the outer conjugate minus 9-10 cm.
The true conjugate is equal to the diagonal conjugate minus 1.5-2 cm.
For thick bones, the maximum number is subtracted; for thin bones, the minimum number is deducted. To assess bone thickness, the Solovyov index (wrist circumference) has been proposed. If the index is less than 14-15 cm, the bones are considered thin, if more than 15 cm, the bones are considered thick. The size and shape of the pelvis can also be judged by the shape and size of the Michaelis diamond, which corresponds to the projection of the sacrum. Its upper corner corresponds to the suprasacral fossa, the lateral corners correspond to the posterosuperior iliac spines, and the lower corner corresponds to the apex of the sacrum.
The dimensions of the exit plane, as well as the external dimensions of the pelvis, can also be measured using a pelvis gauge.
The angle of inclination of the pelvis is the angle between the plane of its entrance and horizontal plane. When a woman is in an upright position, it is 45-55 degrees. It decreases if the woman squats or lies in a gynecological position with her legs bent and brought toward her stomach (a possible position during childbirth).
The same provisions allow you to increase the direct size of the exit plane. The angle of inclination of the pelvis increases if a woman lies on her back with a bolster under her back, or if she bends backward in an upright position. The same happens if a woman lies on a gynecological chair with her legs down (Walcher position). The same provisions allow you to increase the direct size of the entrance.
A - head above the entrance to the pelvis
B - head as a small segment at the entrance to the pelvis
B - head with a large segment at the entrance to the pelvis
G - head in the wide part of the pelvic cavity
D - head in the narrow part of the pelvic cavity
E - head at the pelvic outlet
The head is movable above the entrance.
In the fourth step of the obstetric examination, it is determined in its entirety (between the head and the upper edge of the horizontal branches of the pubic bones, you can freely bring the fingers of both hands), including its lower pole. The head moves, that is, it easily moves to the sides when it is pushed away during external examination. During vaginal examination, it is not achieved, the pelvic cavity is free (the boundary lines of the pelvis, promontory, inner surface of the sacrum and symphysis can be palpated), it is difficult to reach the lower pole of the head if it is fixed or displaced downward with an externally located hand. As a rule, the sagittal suture corresponds to the transverse size of the pelvis; the distances from the promontory to the suture and from the symphysis to the suture are approximately the same. The large and small fontanelles are located on the same level.
If the head is located above the plane of the entrance to the pelvis, its insertion is absent.
The head is a small segment at the entrance to the small pelvis (pressed against the entrance to the small pelvis). In the fourth step, it is palpated all over the entrance to the pelvis, with the exception of the lower pole, which has passed the plane of the entrance to the pelvis and which the examining fingers cannot cover. The head is fixed. It can be moved up and to the sides when applying a certain force (it is better not to try to do this). During an external examination of the head (both with flexion and extension insertions), the palms of the hands fixed on the head will diverge, their projection in the pelvic cavity represents the tip of an acute angle or wedge. With occipital insertion, the area of the back of the head accessible to palpation is 2.5-3.5 transverse fingers above the ring line and from the front part - 4-5 transverse fingers. During vaginal examination, the pelvic cavity is free, the inner surface of the symphysis is palpated, the promontorium is difficult to reach with a bent finger or is unreachable. The sacral cavity is free. The lower pole of the head may be accessible for palpation; when pressing on the head, it moves upward outside the contraction. The large fontanel is located above the small one (due to the flexion of the head). The sagittal suture is located in transverse size(may make a small angle with it).
The head is a large segment at the entrance to the small pelvis.
The fourth technique determines only a small part of it above the entrance to the pelvis. During external examination, the palms, tightly applied to the surface of the head, converge at the top, forming with their projection an acute angle outside the large pelvis. The part of the back of the head is determined by 1-2 transverse fingers, and the front part - by 2.5-3.5 transverse fingers. During vaginal examination top part the sacral cavity is filled with the head (the promontory, the upper third of the symphysis and the sacrum are not palpable). The sagittal suture is located in the transverse dimension, but sometimes with small sizes of the head one can also notice its beginning rotation. The cape is unreachable.
The head is in the wide part of the pelvic cavity.
During external examination the head is not detected ( occipital part the head is not determined), the front part is determined by 1-2 transverse fingers. During vaginal examination, the sacral cavity is filled in most of it (the lower third of the inner surface of the pubic joint, the lower half of the sacral cavity, the IV and V sacral vertebrae and the ischial spines are palpated). The contact zone of the head is formed at the level of the upper half of the pubic symphysis and the body of the first sacral vertebra. The lower pole of the head (skull) may be at the level of the apex of the sacrum or slightly lower. The arrow-shaped seam can be in one of the oblique sizes.
The head is in the narrow part of the pelvic cavity.
During vaginal examination, the head is easily reached, the sagittal suture is in an oblique or straight size. Inner surface pubic joint is unattainable. Pushing activity began.
The head is on the pelvic floor or at the pelvic outlet.
External examination fails to identify the head. The sacral cavity is completely filled. The lower pole of contact of the head passes at the level of the apex of the sacrum and lower half pubic symphysis. The head is located immediately behind the genital slit. Arrow-shaped seam in straight size. When pushing, the anus begins to open and the perineum protrudes. The head, located in the narrow part of the cavity and at the outlet of the pelvis, can also be felt by palpating it through the tissue of the perineum.
According to external and internal studies, a coincidence is observed in 75-80% of examined women in labor. Different degrees of flexion of the head and displacement of the skull bones (configuration) can change the data of the external examination and serve as an error in determining the insertion segment. The higher the experience of the obstetrician, the fewer errors are made in determining the segments of head insertion. The vaginal examination method is more accurate.
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