Diagnosis of a narrow pelvis

In the clinical aspect, diagnostics of a narrow pelvis should consist of a carefully collected anamnesis, a general examination of the pregnant woman or woman in labor, and an internal examination. The doctor receives the most significant data when collecting anamnesis - finding out the age, previous general and infectious diseases that can adversely affect the general development of the body (infantilism, hypoplasia) and the correct formation of the pelvis (rickets, bone tuberculosis).

The most significant obstetric anamnesis are: late onset of menstruation, disturbance of their rhythm, protracted previous labor with weak labor, operative delivery, especially cesarean section, uterine perforation and conservative myomectomy, fetal-destroying operations, and delivery of a large fetus.

During a general external examination, attention is paid to height - small - 155-145 cm and below, as a prerequisite for a generally uniformly narrowed pelvis; large - 165 cm and above - a funnel-shaped pelvis; signs of rickets - flat rachitic, as well as a simple flat pelvis; lameness, shortening of the leg, change in the shape of the hip joints (one or two) - the presence of obliquely narrowed pelvises.

The most important for clarifying the shape and especially the degree of narrowing of the pelvis is a vaginal examination to determine the diagonal conjugate for the most common shapes of pelvises - generally uniformly narrowed and flat: for rare pelvises (irregular shape) - identifying the capacity of the halves of the pelvis, along with measuring the diagonal conjugate.

To judge the degree of narrowing of the kyphotic pelvis, it is necessary to measure the direct and transverse dimensions of the pelvic outlet - the latter normally has a round shape with a diameter of the indicated dimensions of 10.5-11 cm.

The mechanism or biomechanism of labor in narrow pelvises, especially typical and most common, has been well studied. It is quite specific in nature, consisting of adaptive movements of the head to overcome individual obstacles or general narrowing of the pelvis. In addition, a birth tumor and configuration of the head are formed, which reduces its size, facilitating passage through the pelvis narrowed for it. Without knowledge of these features, it is impossible to understand the course or conduct labor in one or another form of narrow pelvis.

Among the absolute indications for cesarean section, it is necessary to name anatomically narrow pelvis of the III degree (true conjugate less than 7 cm), sometimes of the II degree in the presence of a large fetus, as well as clinical discrepancy between the woman's pelvis and the fetal head.

Relative indications may include anatomically narrow pelvis of grades I and II with a true conjugate of 11 to 7 cm. When deciding on abdominal delivery, the combination of an anatomically narrow pelvis with the woman's advanced age, a history of stillbirth, breech presentation, large fetus, incorrect insertion of the head, etc. may also be important; the doctor promptly refers such women from high-risk groups to a qualified obstetric facility.

Recently, due to the more frequent development of large fetuses, an unfavorable obstetric situation is often observed with normal pelvic dimensions and especially with its initial narrowing. A picture of relative, and sometimes more pronounced clinical insufficiency is created. A large head remains mobile or weakly pressed to the entrance to the pelvis for a relatively long time. This excessively stretches the lower segment during contractions, preventing it from contracting properly, which is currently considered necessary for the normal course of labor, leading to a slow opening of the cervix. In this case, uncoordinated labor often occurs, accompanied by untimely discharge of amniotic fluid and the development of weakness of labor. The absence of the formation of a birth tumor and a sufficient configuration of the head to overcome the known resistance from the pelvis creates the prerequisites for the development of a clinically narrow pelvis. While previously the vast majority of births, even with grade I pelvic narrowing, ended spontaneously in 80-90%, currently, due to the large number of large fetuses, the passage of a large head encounters significant, difficult to overcome obstacles, even with normal pelvic sizes.

The use of antispasmodics, timely provision of sleep-rest with subsequent or preliminary creation of an estrogen-glucose-vitamin-calcium background, as well as the intravaginal use of a gel with prostaglandins and the use of labor stimulation, along with the prevention of infection and measures that improve the vital activity of the intrauterine fetus, allows for the completion of labor through the natural birth canal.

Often, for the fastest possible opening of the cervix and the elimination of painful and unproductive contractions and the normalization of labor, epidural analgesia, which should be performed by a highly qualified anesthesiologist, has a beneficial (antispasmodic and analgesic) effect. To prevent the development of large fetuses, it is necessary to more actively regulate the excess weight of large fetuses with dietary and other measures, since the existing acceleration of the intrauterine fetus, with the preserved normal size of the pelvis in women, creates certain difficulties in labor.

There is a high frequency and manifestation of various complications during labor with a narrow pelvis. There are general complications observed with all narrow pelvises, and some of them are characteristic of individual types (varieties) of narrow pelvises, associated with the specificity of the labor mechanism.

A common complication of narrow pelvises is the untimely (both premature and early) discharge of waters, observed 5 times more often than usual. This is usually explained by the prolonged standing of the head, mobile above the entrance to the pelvis or at the entrance to the small pelvis. This is more often observed in flat pelvises, where the girdle of contact of the head with the plane of the entrance to the pelvis is not formed sufficiently, and less often - in a generally uniformly narrowed pelvis. This also explains the more frequent prolapse of small parts of the fetus and the especially unfavorable prolapse of the umbilical cord loops; a slower opening of the cervix (collapse of its edges after the discharge of waters and the absence of passage of the head), leading to protracted labor and a long anhydrous interval and fatigue of the woman in labor. An even more unfavorable complication is the addition of an infection (fever during labor and endometritis) and asphyxia of the intrauterine fetus. The development of primary weakness of labor activity is often noted, especially in primiparous women. This is due to the need for a long time to overcome the obstacles of a narrowed pelvis. In primiparous women, this complication is often associated with general underdevelopment and infantilism, in multiparous women - with overstretching of the uterine muscles, altered by previous protracted labor. Secondary weakness of labor activity often develops.

With a high or only pressed head and incomplete opening of the cervical os, the appearance of untimely or false attempts is noted as an expression of the presence of an obstacle to the advancement of the head. This, according to French authors, is the "cry" of a narrow pelvis. Long standing of the head in one plane of the pelvis causes painful, intense, sometimes convulsive contractions, which is sometimes fraught with overstretching of the lower segment of the uterus with a high standing of the border ridge (Schatz-Unterberger groove). This is also a signal of a threatening or incipient rupture of the uterus (the appearance of serous discharge). The lack of advancement of the head is also important for compression of soft tissues (their ischemia), the bladder (the appearance of blood in the urine), and in the absence of due attention to these threatening symptoms on the part of the doctor, tissue necrosis and the formation of urogenital fistulas may be observed in the future.

Pinching of the anterior lip of the cervix, manifested by bloody discharge, painful involuntary pushing, requires timely tuck-in of the cervix to avoid its trauma and facilitate the advancement of the head. Sharply difficult passage of the head, especially a large one, through a narrowed pelvis, as well as the use of obstetric operations (application of forceps, especially abdominal, or a vacuum extractor) can lead to rupture of the pubic symphysis.

Often, a narrow pelvis is the cause of incorrect positions of the fetus and insertions of the head (mainly extension), passing it with large dimensions, which usually creates additional difficulties and can lead to phenomena of a clinically narrow pelvis.

There are a significant number of other complications with a narrow pelvis that the doctor should not forget about. Thus, the number of cases of untimely rupture of waters (more than every third woman in labor), fever during labor (every tenth), intrauterine asphyxia of the fetus (almost half of women with a narrow pelvis) is especially high.

The large number of fetal life disorders is partly explained by the fact that in modern conditions they are established using hardware research methods (cardiotocography) without obvious clinical manifestations of changes in the auscultatory (obstetric stethoscope) nature of the fetal heartbeat or the presence of meconium in the amniotic fluid.

Instrumental measurement of the pelvis. With a pelvis meter, the distance between certain points of the skeleton - bone protrusions - is measured in the woman's lying position. Three transverse dimensions are measured:

1. distance between the spines (distantia spinarum) equal to 25-26 cm;
2. distance between combs (distantia cristarum) equal to 28-29 cm;
3. distance between the greater trochanters (distantia trochanterica), equal to 30-31 cm.

In this case, the ends of the compass are placed on the most prominent points of the anterior superior spines, on the most prominent points of the pectineal bones and the prominent points of the outer surface of the greater trochanters.

When measuring the external direct size of the pelvis, the woman is in a side position, with the leg on which the woman is lying bent at the hip and knee joints, and the other leg extended. One leg of the pelvimeter is placed on the anterior surface of the symphysis near its upper edge, and the other - in the depression between the last lumbar and 1 sacral vertebrae - in the upper corner of the Michaelis rhombus. This is the external direct size, or external conjugate, which is normally equal to 20-21 cm. It can also be used to judge the size of the internal true conjugate, for which it is necessary to subtract 9.5-10 cm from the size of the external conjugate. The internal direct size is 11 cm.

There is another dimension - the lateral conjugate. This is the distance between the anterosuperior and posterosuperior iliac spines on the same side, which allows us to judge the internal dimensions of the pelvis; normally it is 14.5-15 cm, and with flat pelvises - 13-13.5 cm.

When measuring the transverse size of the pelvic outlet, the tips of the pelvis meter are placed on the inner edges of the ischial tuberosities and 1-1.5 cm are added to the resulting figure of 9.5 cm for the thickness of the soft tissues. When measuring the direct size of the pelvic outlet, the tips of the compass are placed on the top of the coccyx and on the lower edge of the symphysis and 1.5 cm are subtracted from the resulting value of 12-12.5 cm for the thickness of the sacrum and soft parts. The thickness of the pelvic bones can be judged by the Soloviev index - the area of the circumference of the wrist joint, which for a woman of normal build is 14.5-15.5 cm.

Next, it is necessary to use Leopold's techniques to determine the position of the fetus, its type, position and presenting part. It is very important to determine the position of the head in relation to the plane of the entrance and the pelvic cavity, which is important for understanding the biomechanics of labor.

1. A head high above the pelvic inlet or "balloting" of the head indicates that the latter moves freely to the side when moved by the obstetrician's hand.
2. The head is pressed to the entrance to the pelvis - such displacements of the head cannot be made, moving the head by hand is difficult. Further, a distinction is made between insertion of the head into the pelvis by a small, medium and large segment. The expression: "the head by a large segment at the entrance to the pelvis" is replaced by some obstetricians with the expression "the head in the upper part of the pelvic cavity". The head by a small segment - when only an insignificant part or pole of the head is located below the plane of the entrance to the pelvis. The head by a large segment - is installed at the entrance to the pelvis with the suboccipital fossa and frontal tubercles and the circle drawn through the indicated anatomical boundaries will be the base of the large segment. The head is in the pelvic cavity - the head is located entirely in the cavity of the small pelvis.

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