External oblique dimensions of the pelvis. Small pelvis of a woman

The biomechanism of childbirth includes a sequence of actions that a child performs while passing through the birth canal. With normal passage, it does not encounter obstacles, and delivery occurs without complications. The abnormal structure of the pelvis, for example, its narrowing, disrupts the biomechanism of the birth process and leads to grave consequences for the mother and baby. The width of the pelvic cavity depends on the method of childbirth. How to calculate the size of the pelvis in a pregnant woman, and what are the consequences of a violation of the norm?

Why is it important to know the size of the pelvis during pregnancy?

The pelvic cavity is the space inside the body that is surrounded by pelvic bones. This is where the bladder and organs are located. reproductive system. In front, the cavity is covered by the pubic symphysis - connection pubic bones, and behind - the sacrum and coccyx.

Why does a gynecologist need to know the size of the female pelvis during pregnancy? This is required to identify discrepancies between the size of the pelvic space and the baby's head. If the baby is large and the pelvis is narrow, then childbirth will take place with complications. According to the structure of the female pelvis, doctors choose the method of childbirth - whether the process will be natural or surgical intervention will be required.

Methods for diagnosing the size of the pelvis in pregnant women

Gynecologists are interested in the size of the pelvis of a pregnant woman in order to find out if the baby's head can pass through the existing hole. It is almost impossible to measure the bone birth canal in a woman in position, because it is covered by the pelvic bones, skeletal muscles and skin, and to conduct an examination, one would have to use an x-ray, so obstetricians measure external parameters, and then, using special formulas, calculate internal ones.

To measure the pelvis, a tazometer is used - a device resembling a compass, with centimeter and millimeter divisions. The pelvis is measured in lying position, the doctor applies a device in a woman and takes measurements.

Measurement parameters:

1. Rhombus of Michaelis, or sacral rhombus. It is located in the lumbar region and externally looks like a rhombus. Normally, the dimensions of the Michaelis rhombus are 11 cm. The pathology is indicated not only by the deviation in size, but also by the distortion of the shape, which indicates a curvature of the spine or small pelvis.
2. Spinarum distance - measurement of the line between the anterior superior iliac spines.
3. Cristarum distance - a line connecting the most prominent areas of the ilium.
4. Trochanteric distance - the distance between the tubercles at the neck thigh bones. Knowing these three distances, you can calculate the difference between them, which should be within 3 cm.
5. External conjugate - measurement of the line between top pubic bone and sacral rhombus. Knowing this value, one can calculate the internal or true conjugate- the circumference of the entrance to the small pelvis.
6. Diagonal conjugate - the distance that is measured between the lower end of the articulation and the protruding part of the sacrum. The diagonal value is measured during vaginal examination. Not always the gynecologist can feel the bone from the inside, then the pelvis is considered normal. The diagonal conjugate is normally 12-13 cm.

Since doctors can only calculate the external parameters of the pelvis, it is important for them to be aware of the errors in the calculations, which can be affected by the size of the bones themselves. To do this, measure the female wrist - if the circumference is more than 14 cm, then the woman has wide bones, and the distance between them will be less than that obtained in the calculations.

Table of normal indicators of the size of the pelvis

The values ​​obtained are compared with the normative indicators suitable for natural childbirth. Deviations up or down indicate that the pelvis is too narrow or too wide.

The table shows the normal size of the pelvis:

How is the true conjugate calculated if it cannot be measured? To do this, the number 9 is subtracted from the distance between the pubic joint and the sacral rhombus. If the circumference of the wrist is more than 14-15 cm, then you need to subtract 10 cm even with a normal external conjugate, the true one will be too small.

Narrow pelvis and its consequences

An anatomically narrow pelvis is said to be when there is a deviation from the standard sizes down by 1 cm or more. The more significant the deviation, the higher the degree of narrowness. There are the following degrees of narrowing:

• transversely narrowed;
• flat;
• generally uniformly narrowed;
• oblique;
• flat-rachitic;
• post-traumatic.

In obstetric practice, transversely narrowed and flat varieties of narrowing of the pelvis are common. The development of bones is influenced by the processes occurring in the embryonic period of a girl's development. If the embryo in embryogenesis does not receive enough vitamins and minerals, the mother consumes harmful substances and illegal drugs, this affects the development of the musculoskeletal system.

Bone curvature occurs as a result of infectious and non-infectious ailments, which the girl had been ill with in prepubertal and puberty- tuberculosis, poliomyelitis, spinal injury, scoliosis. Professional sports in preschool and junior school age may also contribute to pelvic deformity.

With a small narrowing, independent childbirth is allowed if the baby is small, otherwise the woman is sent for surgery. Risks during gestation and childbirth:

• exfoliation of the placenta;
• rupture of internal organs;
• oxygen starvation;
• birth trauma at the baby.

The diagnosis of "clinically narrow pelvis" is made when the pelvic space is anatomically correct, but the baby is too large and unable to pass the birth canal without the threat of injury. This condition cannot be tracked in advance, it is determined either before the birth itself on an ultrasound scan, or during delivery. The fetus literally gets stuck inside, which without surgical intervention leads to lethal outcome for baby or woman.

Why is a wide pelvis dangerous?

When the small pelvis deviates from the normative sizes to the large side, they speak of a wide pelvic cavity. This is not uncommon for tall and large women. Such a structure is not considered a pathology, but obstetricians carefully monitor the process of delivery.

With a wide pelvis, the child does not experience obstacles and quickly passes through the birth canal. This is precisely the danger. The tissues do not have time to adapt, gradually stretch and miss the baby, so the risk of ruptures increases.

Features of the conduct of childbirth in case of deviations in the size of the pelvis from the norm

If the decision is made to give birth independently, then from medical workers maximum care is required. The life and health of the woman in labor and the baby depend on the actions of doctors.

Before giving birth, a pregnant woman is prescribed bed rest, she is hospitalized in the last weeks of pregnancy. Need to calm down to maintain integrity amniotic sac and avoid premature outflow of water.

After the water has broken, the doctor will perform a vaginal examination to see if the cord has prolapsed. When the loop falls out, it is pinched, and the child stops receiving oxygen, hypoxia occurs.

During the birth process, doctors continuously monitor the condition of the woman using a cardiotocograph, which registers uterine contractions. If there is a threat to health, the expectant mother is taken to the operating room, where an urgent C-section. If the delivery goes naturally, often you have to do an episiotomy - an incision in the perineum.

1. Distantia spinarum - the distance between the anterior-superior iliac spines is 25-26 cm.
2. Distantia cristarum - the distance between the distant points of the iliac crests is 28-29 cm.
3. Distantia trochanterica - the distance between the large trochanters of the femur, normally 30-31 cm.
4. Conjugata externa (external conjugate, direct size of the pelvis) - the distance from the middle of the upper outer edge of the symphysis to the supra-sacral fossa, located between the spinous process V lumbar vertebra and the beginning of the middle sacral crest (coinciding with the upper corner of the Michaelis rhombus), is 20-21 cm.

Small pelvis dimensions

1. The plane of entry into the pelvis is limited by the upper edge of the symphysis, the upper-inner edge of the pubic bones (in front), the arcuate lines of the ilium (from the sides), and the sacral promontory (behind). This border between the large and small pelvis is called the boundary (nameless) line.

• Conjugata vera (true conjugate, direct size of the entrance to the small pelvis) - the distance from the inner surface of the symphysis to the cape of the sacrum; to determine the true conjugate, subtract 9 cm from the dimensions of the outer conjugate. Normally, the true conjugate is 11 cm.
• Anatomical conjugate - the distance from the cape to the middle of the upper inner edge of the symphysis (11.5 cm).
• Transverse size - the distance between the most distant points of the arcuate lines (13-13.5 cm).
• The oblique dimensions are 12-12.5 cm. The right oblique dimension is the distance from the right sacroiliac joint to the left iliopubic eminence (eminentia iliopubica). Left oblique size - the distance from the left sacroiliac joint to the right iliopubic eminence (eminentia iliopubica).

2. The plane of the wide part of the pelvic cavity is limited by the middle of the inner surface of the symphysis (in front), the middle of the acetabulum (from the sides) and the junction of the II and III sacral vertebrae (behind).

• Direct size - the distance from the junction of the II and III sacral vertebrae to the middle of the inner surface of the symphysis is 12.5 cm.
• Transverse size - the distance between the middle of the acetabulum (12.5 cm).

3. The plane of the narrow part of the pelvic cavity is limited by the lower edge of the symphysis (in front), the spines of the ischial bones (from the sides) and the sacrococcygeal junction (behind),

• Direct size - the distance from the sacrococcygeal junction to the lower edge of the symphysis (11-11.5 cm).
• Transverse size - the distance between the spines of the ischial bones (10.5 cm).

4. The plane of the exit of the pelvis is limited by the lower edge of the symphysis (in front), ischial tubercles (from the sides) and the tip of the coccyx (behind).

• Direct size - from the top of the coccyx to the lower edge of the symphysis (9.5 cm). When the coccyx moves backward during childbirth - 11.5 cm.
• Transverse size - the distance between the inner surfaces of the ischial tubercles (11 cm).

sacral rhombus

When examining the pelvis, pay attention to the sacral rhombus (Michaelis rhombus) - a platform on the back surface of the sacrum. Borders: upper corner - a depression between the spinous process of the V lumbar vertebra and the beginning of the middle sacral crest; lateral angles - posterior superior iliac spines; lower - the top of the sacrum. From above and outside, the rhombus is bounded by protrusions of large spinal muscles, from below and outside - protrusions of the gluteal muscles.

Accurate determination of the size of the pelvis in obstetrics before the onset of labor can save the life of the woman in labor and the child. Every woman goes through this procedure, since with its help it is possible to understand in advance whether a caesarean section is required. In gynecology, the dimensions of the large and small pelvis are measured, each distance has its own name and standards. For the procedure, a special tool is used - a medical metal compass - a tazomer.

The main parameters of the large pelvis

female pelvis significantly different in size from the male. It is important for a girl to know a few parameters and their meanings in order to make sure that the doctors are acting correctly:

1. Spinarum distance - normally 25-26 cm - this is the distance between the anterior superior awns of the bones of the iliac zone.
2. Cristarum distance - normal 28-29 cm - the position of the distant capes of the iliac crests located above the mount hip joint.
3. External conjugate - from 20 to 21 cm - the distance from the middle of the top of the symphysis to the upper corner of the Michaelis rhombus.

The awn is an acute formation on the bones, which is diagnosed both in normal and in various diseases. Osteophytes and osteoporosis are derivatives of this word.

Narrowing of the female pelvis is a common obstetric problem. This indicator matters:

• at grade 1 - the easiest - the true conjugate retains a size greater than 9, but less than 11 cm;
• with 2 degrees of narrowing of the pelvis, this figure is 7 and 9 cm, respectively;
• at 3 degrees - 5 and 7 cm;
• at grade 4, the true conjugate barely reaches 5 cm.

The true conjugate of the pelvis is the distance from the protruding part of the sacrum to the superior cape of the pubic symphysis at the exit. The easiest way to determine the parameter is by the dimensions of the conjugates outside.

The true conjugate is shortest distance inside, through which the fetus comes out during childbirth. If the indicator is less than 10.5 cm, then natural childbirth doctors forbid. The true conjugate parameter is set by subtracting 9 cm from the external indicator.

The diagonal conjugate is the distance from the bottom of the pubic joint to the prominent point of the sacrum. It is determined using vaginal diagnostics. At normal pelvis the indicator does not exceed 13 cm, it happens at least 12 cm. To clarify the true conjugates, 1.5-2 cm are subtracted from the resulting figure.

When examining the diagonal indicator, the doctor in rare cases reaches with fingers to the cape of the sacrum. Usually, if the bone is not felt when the fingers are placed inside the vagina, the size of the pelvis is considered normal.

The shape of the pelvis can affect normal performance. With a platipelloid constitution, which occurs in 3% of women, the pelvis is elongated, slightly flattened. In this case, the gap between the bones narrows, as a result of which the process of childbirth can be complicated.

Pelvic planes

To understand exact specifications of the female skeleton, it is necessary to measure the plane before childbirth:

1. Entry plane. In front, it starts from the top of the symphysis and reaches the promontory posteriorly, and the lateral distance borders on the innominate line. The direct size of the entrance corresponds to the true conjugate - 11 cm. The transverse size of the 1st plane is located between the distant points of the boundary lines, at least 13 cm. The oblique dimensions start from the sacroiliac joint and continue to the pubic tubercle - from 12 to 12.5 cm is normal. The entrance plane usually has a transverse oval shape.
2. The plane of the wide part. Runs through inner surface the womb is strictly in the middle, runs along the sacrum and the projection of the acetabulum. Possesses round shape. The direct size is measured, which is normally 12.5 cm. It starts from the middle of the pubic articulation and passes to the 2nd and 3rd vertebrae of the sacrum above the buttocks. The transverse size of the zone is 12.5 cm, measured from the middle of one plate to the other.
3. The plane of the narrow part. It starts from the bottom of the symphysis and comes back to the sacrococcygeal joint. The plane is limited on the sides ischial spines. The straight size is 11 cm, the transverse size is 10 cm.
4. exit plane. It connects at an angle the lower edge of the symphysis with the edge of the coccyx, along the edges it goes into the ischial bones located in the area of ​​the buttocks. The direct size is 9.5 cm (if the coccyx is rejected, then 11.5 cm), and the transverse size is 10.5 cm.

In order not to get confused in all indicators, you can pay attention only to the measurement of the large pelvis. The table shows an additional parameter - the distance between the skewers of the thighs.

The trochanters of the femur are located at the point where girls usually measure the volume of the hips.

Determining the size of the pelvis: narrow or wide

Comparing the obtained indicators, it is easy to determine whether a woman has wide or narrow hips. After consulting with a gynecologist and determining whether the size of the female pelvis is normal, you can decide whether to do a caesarean section or give birth on your own.

Indicators are above the norm

In most cases, a wide female pelvis - good factor for pregnancy. Girls must understand that if a woman loses weight, the pelvis cannot become narrower because of this - everything is inherent in the structure of the bones. Wide hips are most often found in large women, and this cannot be considered a pathology. If the dimensions exceed the norm by 2-3 centimeters, this is considered a wide pelvis.

The main danger of too wide hips is rapid childbirth. In this situation, the child passes much faster through birth canal, which can lead to women's injuries: rupture of the cervix, vagina and perineum.

Anatomically narrow pelvis

The definition of an anatomically narrow pelvis in obstetrics is closely related to normal indicators. A deviation of 1.5 cm from the minimum limit indicates that the woman has small hips. In this case, the conjugate should be less than 11 cm. Natural childbirth in this case is possible only when the child is small.

When diagnosing, the doctor identifies the type of pelvis: transversely narrowed, evenly narrowed, flat simple or rachitic. Less common pathological forms in which the pelvis began to narrow pathological changes in the bone structure: kyphotic, deformed, oblique or spondylolisthesis pelvis. Causes of an anatomically narrow pelvis:

• bone injury;
• rickets;
• elevated physical exercise and lack proper nutrition in childhood;
• neoplasms in the study area;
• hyperandrogenism, leading to the formation of the male type;
• accelerated growth during adolescence;
• psycho-emotional stress that caused compensatory development in childhood;
• general physiological or sexual infantilism;
• cerebral palsy, birth trauma, poliomyelitis;
• professional sports;
• metabolic problems;
• dislocations of the hip joints;
• inflammatory or infectious diseases skeletal system;
• rachiocampsis.

Provoke the wrong formation of the pelvis factors such as hormonal imbalance, constant colds and problems with the menstrual cycle.

Clinically narrow pelvis

Clinically, a narrow pelvis can be detected only before childbirth, or during delivery. This is due to the discrepancy between the size of the fetus and the birth canal of a woman. For example, if the child's weight is more than 4 kg, even a girl with normal indicators can be diagnosed with a "clinically narrow pelvis". There is no single answer to the question of why such a state is formed. The doctor identifies a range of reasons:

• large fruit;
• gestation for more than 40 weeks;
• malposition;
• tumors of the uterus or ovaries;
• fetal hydrocephalus (enlarged head);
• fusion of the walls of the vagina;
• breech presentation of the fetus (the child is turned with the pelvis instead of the head).

In obstetric practice, there are more and more cases of a clinically narrow birth canal, because large children are born.

Every woman should find out the parameters of the pelvis before childbirth. A responsible gynecologist never ignores these indicators and carefully conducts a study using an obstetric compass.

The pelvis is a complex of bones that connects lower limbs with the spine. This part of the skeleton is formed by two pelvic bones, the sacrum and the coccyx, which are interconnected by cartilage and ligaments. The paired pelvic bone was formed as a result of fusion of the ilium, pubis and ischium in young people aged 16-18. The female pelvis, unlike the male, is wider, but not as deep.

The optimal size of the pelvis during pregnancy is one of the most important conditions the correct course of the birth act. Any deviation in its structure, deformation threatens with complications during childbirth. The question of how to measure the pelvis for childbirth, and what to do with deviations, is of interest to expectant mothers.

Purpose of the procedure

The pelvic cavity is anatomical space bounded by the pelvic bones. The doctor measures its entry and exit, as well as the distance between the bones, to predict the course of labor.

The bone pelvis is a strong and almost inextensible main birth canal, and the birth itself is subject to complex laws of biomechanics. The fetus in a certain position enters the birth canal, slowly turns and leaves the womb. But sometimes the sizes of the pelvis and the child do not match, then the process is delayed, and in some cases it does not end on its own. And therefore, it is necessary to know the parameters of the pelvis for natural childbirth, because often birth injuries and death of children or mothers are associated with a narrow pelvis.

The main task of the doctor, during the measurement of the pelvis in future mother- to find out what size baby she is able to give birth to, so that neither the fetus nor the woman in labor is harmed. After the procedure, the doctor predicts the course of the upcoming birth process, determines potential problems and ways to solve them. For example, women with a narrow pelvis who cannot give birth on their own are offered a caesarean section.

All measurements are carried out in 4 planes. When measuring the entrance to the pelvis, it is important to determine the direct, oblique and transverse dimensions. In other planes, only 2 main parameters are revealed.

Thus, the procedure allows you to determine the normal size of the pelvis for natural childbirth, as well as identify deviations in time, and develop further tactics actions.

Determining the size of the pelvis

During the procedure, obstetricians determine the dimensions of the small pelvis, which is the very bone birth canal through which the child moves during childbirth. Its internal measurement is technically complex and not safe (using x-rays). Outside, it is covered by the pelvic and femoral bones, muscles and skin. Therefore, the doctor identifies the external dimensions with the help of a tazometer, and then, based on the results obtained, using special formulas, calculates the volume pelvic ring.

During the examination, the pelvis is examined, felt and measured. Special attention give the sacral rhombus (Michaelis rhombus), which allows you to determine the structure of the pelvis. The sacral rhombus is a depression in the lumbosacral region, bounded on all sides by the muscles of the back and buttocks. This formation looks like a regular rhombus, if the figure is not correct, then this indicates pathological processes(eg, pelvic curvature or spinal column). Its normal vertical and horizontal dimensions are 11 cm. There may be a deviation in the direction of increase or decrease by 1 cm, but no more. Otherwise, natural childbirth is in jeopardy.

Measurement of the pelvis of a pregnant woman with a tazometer is carried out by a doctor. The tazometer is measuring device, which looks like a compass. It has a scale with centimeter and half-centimeter divisions. When taking measurements, a woman takes horizontal position and exposes the belly. During the procedure, 4 important parameters are determined:

1. Spinarum distance is the distance between the anterior superior iliac spines. Normal- 26 cm.

2. Distance cristarum - the gap between the most distant points of the ilium. Normally from 28 to 29 cm.

3. The distance of the triangular - the line between the skewers of the femur is 31–32 cm.

4. The conjugate of the externa (straight size of the pelvis) is the line between the upper part of the pubis and the lumbosacral rhombus. normal size- 21 cm normal condition equal to 11 cm. This is the smallest circle in the small pelvis through which the head of the child passes during childbirth. If this parameter is less than 11 cm, then the risk of complicated childbirth increases.

The difference between the distance of spinarum, cristarum and triantheric is very important, normally it is 3 cm. If this value is less, then this indicates a narrowing of the pelvis.
The algorithm for determining the size of the pelvis is quite complicated, and therefore this task falls on the shoulders of a qualified doctor.

Pelvic Size Chart for Natural Birth:

wide pelvis

Sometimes the parameters of the pelvis exceed normal values, then we are talking about a wide pelvis. This is not a pathology, a wide pelvis is typical for large women. In this case, the dimensions of the pelvis are 2–3 cm larger than normal. The birth process proceeds naturally, sometimes rapid childbirth is possible. The child passes through the birth canal faster, as a result of which the risk of ruptures increases.

narrow pelvis

Obstetricians distinguish 2 concepts - a narrow clinical and anatomical pelvis.
With an anatomically narrow pelvis, all or one parameter is less than 2 cm. However, the anatomical narrowing is not as dangerous as it seems, this applies to cases where the fetus is small and its head easily passes through the mother's pelvic ring.

With a clinically narrow pelvis, all sizes can be normal, but if the fetus is large, then there is a discrepancy between the size of its head and the mother's pelvic ring. In this case, natural childbirth threatens dangerous consequences for the child and mother, and therefore surgical intervention is recommended.

Factors that affect the development of a narrow pelvis:

Rickets
Improper nutrition child
cerebral palsy
Infantile spinal palsy
Congenital pathologies pelvis
Pelvic fractures or oncological formations on it
Spinal deformity (eg, scoliosis, kyphosis)
Inflammation or dislocation of the hip joint
Fast growth during puberty.

Gynecologists allocate different forms narrowing of the pelvis:

transversely narrowed;
flat;
generally uniformly narrowed;
oblique;
flat rachitic;
post-traumatic.

The most common forms include a flat or transverse form of narrowing, and the most rare - oblique, flat rachitic, post-traumatic.
A narrow pelvis and other pathologies of the musculoskeletal system occur with insufficient intake useful substances(vitamins and minerals) to the embryo during pregnancy. Such pathologies occur at the end of the first trimester.

Consequences and prevention of a narrow pelvis

The anatomically narrow pelvis is dangerous pathology for a woman who wants to give birth on her own. Due to a narrow or displaced pelvis, the baby cannot go through the normal path during childbirth. Since the risk of injury or even death of the fetus is high, doctors prescribe a cesarean section at 37 weeks for women in labor with this pathology.

With 1 degree of narrowing, a woman can give birth on her own if the fetus is not very large. Possible complications:

Premature discharge of amniotic fluid;
weak generic activity;
premature separation of the placenta from the uterine wall;
rupture of the ligaments of the hip joint;
violation of the integrity of the walls of the uterus;
uterine bleeding;
oxygen starvation of the fetus;
child injury.

With a clinically narrow pelvis, the size of the fetus and the pelvic ring of the mother do not match. A large child cannot pass through the birth canal, this threatens with swelling of the genital organs of the woman in labor and a tumor on the head of the fetus. In this case, a caesarean section is prescribed, as with a narrowing of the 3rd degree.

It is possible to prevent narrowing and deformation of the pelvis even during the period prenatal development. To do this, you need to eat right, exercise regularly physical exercises timely treat infectious and hormonal diseases. It is important to properly organize the mode of work and rest. This is the only way to prevent anatomical narrowing and save a woman from problems during pregnancy and childbirth.

Additional Research

To obtain Additional information about the dimensions of the pelvis, the correspondence of its size to the head of the child, the deformation of the bones, X-ray pelviometry is prescribed. Such a study is allowed to be carried out at the end of pregnancy, when the fetus is already fully formed.
Ultrasound examination is carried out to determine the dimensions of the pelvis, the size of the head of the embryo, its location.

To determine the thickness of the pelvic bones, the doctor measures the wrist joint of the expectant mother using a centimeter tape. The resulting value is called the Solovyov index, normally it is 14 cm. If this parameter exceeds the norm, then the bones are thick and the pelvic ring is narrower than expected, and if less - pelvic cavity wider.

Thus, taking measurements of the pelvis in a pregnant woman is the most important procedure that allows you to predict the course of childbirth and prevent injury or death to the child and mother.

During vaginal examination, the diagonal conjugate is measured (12.5-13 cm). Obstetric conjugate - c. vera (subtract 2 cm from the dimensions of the diagonal conjugate).

The true conjugate is calculated:

along the diagonal conjunct;

by external conjugate;

according to the vertical dimension of the Michaelis rhombus;

using X-ray pelviometry;

according to ultrasound.

The capacity of the small pelvis depends on the thickness of its bones, which is indirectly determined by measuring the circumference of the wrist joint with the calculation of the Solovyov index (13.5-15.5 cm).

Rhombus Michaelis (normal - 11 x 10 cm).

The direct size of the exit of the small pelvis (9.5 cm).

The transverse size of the outlet of the small pelvis (11 cm).

The pubic angle (90 0 -100 0).

External oblique dimensions of the pelvis.

Lateral conjugate (distance between the anterior and posterior superior iliac spines on one side) - 15 cm.

Distance from the anterior-superior spine on one side to the postero-superior spine on the other side (21-22 cm).

Distance from the middle top edge symphysis to posterior superior spines on the right and left (17.5 cm); the difference in size indicates the asymmetry of the pelvis.

Distance from the supra-sacral fossa to the anterior-superior spines on both sides.

Pelvic circumference at the level of the crests iliac bones(85 cm); the same at the level of large skewers (90 - 95 cm).

The height of the fundus of the uterus; abdominal circumference.

Fetal head diameter (12 cm).

The pubosacral size (the distance from the middle of the symphysis to the junction of the 2nd and 3rd sacral vertebrae is a point located 1 cm below the intersection of the diagonals of the Michaelis rhombus - 22 cm); a decrease in this size by 2-3 cm is accompanied by a decrease straight size wide part of the pelvic cavity.

X-ray pelviometry allows you to determine all the diameters of the small pelvis, the shape, the slope of the pelvic walls, the shape of the pubic arch, the degree of curvature and the slope of the sacrum. It is recommended to produce in 38-40 weeks. pregnancy or before labor activity.

Ultrasound examination - ultrasound, is used to diagnose an anatomically narrow pelvis and makes it possible to obtain the value of the true conjugate and the biparietal size of the fetal head, their ratio.

The course of pregnancy and childbirth with a narrow pelvis

A narrow pelvis as such does not lead to a change in the course of pregnancy.

The adverse effect of the narrowed pelvis on the course of pregnancy affects its last months and at the beginning of childbirth.

Features that an obstetrician should know about:

In primiparas, due to a discrepancy between the pelvis and the head, the latter does not enter the pelvis and remains mobile over the entrance throughout pregnancy and at the beginning of childbirth. The height of the fundus of the uterus on the eve of childbirth remains at the same level.

In nulliparous women with a narrow pelvis, by the end of pregnancy, the abdomen has a pointed shape, and in multiparous women it is pendulous.

Anomalies of the pelvis are common causes wrong position fetus - oblique, transverse and breech presentation fetus, also unfavorable insertion of the head - extensor.

One of the most frequent and serious complications pregnancy with a narrow pelvis is a premature (prenatal) outflow of water. This is due to the lack of a contact belt - the head stands high, it does not touch the pelvic ring, so the waters are not divided into anterior and posterior - the entire mass is poured out at the beginning of labor under increasing uterine pressure.

With the outflow of amniotic fluid and the moving head of the fetus, there is a high risk of prolapse of the umbilical cord and small parts of the fetus. Prolapse of the umbilical cord leads to the development of acute hypoxia of the fetus and its death if the head presses it against the pelvic wall. In these cases, only an emergency caesarean section can save the child (intranatal mortality among newborns in these cases is 60-70%).

With a narrow pelvis, childbirth is often complicated by the weakness of labor. Firstly, women with a narrow pelvis have hormonal insufficiency, sexual infantilism, and secondly, childbirth is protracted, which leads to fatigue of the woman in labor, exhaustion energy resources and the development of secondary weakness of labor activity.

Maternal trauma. Prolonged compression fetal head Bladder and rectum can lead to the formation of genitourinary and intestinal-genital fistulas (for 6-7 days). Compression of the cervix can lead to edema, necrosis, deep tears.

The lack of forward movement of the fetus with continued intensive labor activity leads to a gradual thinning of the lower segment and the occurrence of a threatening rupture of the uterus.

At protracted course childbirth with a long anhydrous interval significantly increases the risk of endometritis, chorioamnionitis, ascending infection of the fetus.

Fetal complications. The fetal head configures slowly, lingers for a long time in various planes of the small pelvis, which causes a violation of cerebral circulation, edema, an increase in the volume of the head, the formation of cephalohematomas, subdural and subarachnoid hemorrhages. At further development a child in these areas forms a cicatricial adhesive process, leading to deviations in the neuropsychic sphere and physical development up to the development of hydrocephalus, hyperkinesis, epilepsy and dementia. Moreover, with deep, irreversible violations of brain function, cerebral palsy can form.