Types of labor anomalies

For the successful development of scientific and practical obstetrics, it is of fundamental importance to clarify the causes of abnormalities in labor and the most justified pathogenetic treatment.

The general concept of anomalies of labor activity includes the following types of pathology of contractile activity of the uterus and abdominal press during labor:

• weakness of uterine contractility - primary, secondary, universal;
• weakness of pushing activity - primary, secondary, universal;
• discoordination of labor;
• hyperdynamic labor.

One of the complete systematizations of primary and secondary weakness of labor activity is given in the classification of S. M. Becker.

Classification of anomalies of labor activity depending on the period of their occurrence:

• latent phase (preparatory period according to E. Friedman);
• active phase (period of cervical dilation according to Friedman);
• II stage of labor (pelvic period according to Friedman).

The latent phase, when the cervix is preparing for significant anatomical changes that will occur later, includes only one type of labor anomaly, namely, a prolonged latent phase.

Anomalies of the active phase of labor, characterized by perturbations in the processes of cervical dilation, include:

• prolonged active phase of disclosure;
• secondary arrest of cervical dilation;
• a prolonged slowdown phase.

Anomalies of the second stage of labor include:

• inability to lower the presenting part of the fetus;
• slow descent of the presenting part of the fetus;
• stopping the descent of the presenting part of the fetus.

Finally, there is an anomaly that is characterized by excessive labor activity (rapid labor). All eight types of labor anomalies are presented below.

The period of childbirth	Anomalies
Latent phase	Prolonged latent phase
Active phase	Prolonged active phase of cervical dilation
	Secondary arrest of cervical dilation
	Prolonged deceleration phase
II stage of labor	Inability to lower the presenting part of the fetus
	Delayed descent of the presenting part of the fetus
	Stopping the descent of the presenting part of the fetus
All periods	Rapid labor

Recognition of the above anomalies is not difficult if the obstetrician uses a graphical analysis of labor (partogram). For this purpose, the course of cervical dilation and descent of the presenting part of the fetus is marked on the ordinate axis, and time (in hours) is marked on the abscissa axis. Diagnosing labor anomalies without a partogram is inaccurate and often leads to errors.

Most of the modern knowledge about labor and its anomalies is associated with the works of Emanuel A. Friedman. Beginning in 1954, he published the results of clinical studies concerning labor; thus, a scientific work was gradually created that remains indisputably valuable both for its breadth and for the conclusions presented in it. Friedman gave a scientific basis for the clinical evaluation of labor and made the mechanism of labor and its anomalies quite understandable. The main information is presented in the monograph by E. Friedman: “Labor: Clinical Evaluation and Management” (1978) (Emanuel A. Friedman. Labor clinical, evaluation and management Second edition, New York, 1978). At the end of the monograph, the author cites more than 20 books reflecting various types of labor anomalies in the literature.

Classification of causes of weakness of labor activity

Causes of primary weakness of labor.

A. Anatomical and functional insufficiency of the neuromuscular apparatus of the uterus:

1. overstretching of the uterus;
2. birth trauma of the uterus;
3. surgical trauma of the uterus;
4. uterine tumors;
5. chronic inflammatory changes in the tissues of the uterus.

B. Hormonal insufficiency.

B. Acute general febrile diseases.

G. General chronic diseases.

D. Other reasons:

1. decreased excitability of nerve centers;
2. influence of psychogenic factors;
3. reflex weakness of labor;
4. avitaminosis.

Causes of secondary weakness of labor.

A. Causes that cause the occurrence of primary weakness.

B. Functional insufficiency of the abdominal press.

B. Fatigue of the mother in labor.

G. Incorrect management of labor:

1. untimely rupture of the amniotic sac;
2. cervical lip infringement;
3. failure to recognize a narrow pelvis, incorrect positioning of the head or position of the fetus in a timely manner;
4. inept pain relief during labor.

D. Relative obstacles from the pelvis and soft tissues of the birth canal:

1. anatomical narrowing of the pelvis;
2. rigidity of the cervical tissue;
3. cicatricial changes in the soft tissues of the birth canal.

E. Various reasons:

1. compression of intestinal loops;
2. inept use of labor-inducing agents.

Classification of anomalies of labor activity (Yakovlev I.I., 1961)

The nature of uterine contractions.

Hypertonicity: spasmodic contraction of the uterine muscles:

• with complete spasm of the uterine muscles - tetany (0.05%);
• partial spasm of the uterine muscles in the area of the external os at the beginning of the first stage of labor; the lower segment of the uterus at the end of the first and beginning of the second stage of labor (0.4%).

Normotonus:

• uncoordinated, asymmetrical contractions of the uterus in its different parts, followed by the cessation of contractile activity, the so-called segmental contractions (0.47%);
• rhythmic, coordinated, symmetrical contractions of the uterus (90%);
• normal contractions of the uterus, followed by weakness of labor, the so-called secondary weakness of contractions.

Hypotonicity, or true inertia of the uterus, the so-called primary weakness of contractions:

• with a very slow increase in the intensity of contractions (1.84%);
• without a pronounced tendency towards an increase in the intensity of contractions throughout the entire period of labor (4.78%).

Of the indicators characterizing the condition of the pregnant and laboring uterus, the most important are tone and excitability. In most women in labor, the etiopathogenesis of uterine contractile dysfunction (weakening or complete cessation of contractions or disorganization of the nature of the latter) is not smooth muscle fatigue, but disorders of the nervous system. In some cases, vegetative-dysfunctional disorders come to the fore, and in others - neurotic manifestations that cause a disorder of uterine contractility. Tonus is a biophysical state of the smooth muscles of the uterus, one of the elements of contractile activity, performing its function due to the elastic properties of smooth muscles. Tonus characterizes the working readiness of the organ for active activity. Due to tone, the uterus has the ability to maintain a state necessary for the implementation of certain of its functions for a long time. In practice, a distinction is made between normotonus, hypo- and hypertonus. The opening of the pharynx, i.e. the phenomenon of retraction, depends, firstly, on the movement of muscle fibers, the angle of inclination of which becomes steeper, which was shown back in 1911 by N. Z. Ivanov.

In this case, if the general resting tone of the uterus is low, then before the contraction occurs, the walls of the uterus must gradually come into a state of tension. If the resting tone is high, then the slightest contraction of the motor part of the uterus will be reflected in the cervix, the fibers of which are tense and cause opening.

Thus, the significance of the initial high tone of the uterus consists in the rapid transfer of the force of uterine contractions of the motor part of the uterus to the os, and the opening of the latter occurs quickly. Another significance of the tone consists in maintaining the achieved level of opening of the cervix. It can be assumed that a moderately high tone is a favorable moment for rapid opening and rapid labor.

On the other hand, excessively high uterine tone can lead to complications described by Phillips (1938) in the form of labor pains in the absence of contractions and by Lorand (1938) under the name "spastic weakness of labor". There is a direct relationship between resting tone and contraction amplitude according to Wolf - with an increase in resting tone, there is a decrease in contraction amplitude. Therefore, the magnitude of contraction amplitude does not affect the course of labor if there is sufficient tone.

Classification of anomalies of labor [Caldeyro-Barcia, 1958]

The author distinguishes the following anomalies of labor.

1. Quantitative anomalies of uterine contractions. In this group of women in labor, the waves of uterine contractions have a normal quality, i.e. they have a normal coordination with a "triple descending gradient".
   • Hyperactivity. The uterus is considered hyperactive when its contractions have an abnormally high intensity (over 50 mm Hg) or an abnormally high frequency (over 5 contractions in 10 min), i.e. when the uterine activity - the product of intensity and frequency - is higher than 250 mm Hg in 10 min in Montevideo units. Abnormally high frequency of contractions in the works of foreign authors is called tachysystole, it leads to a special type of hypertensive uterus.
   • Hypoactivity. The uterus is considered hypoactive when contractions have an abnormally low intensity (below 30 mm Hg) or an abnormally low frequency (less than 2 contractions in 10 min). When the uterine activity is less than 100 Montevideo units, labor progresses more slowly than normal. Clinicians regard this condition as hypotonic or normotonic weakness of labor (uterine inertia according to the terminology of foreign authors). The causes of uterine hypoactivity are not yet well known.
2. Qualitative anomalies of uterine contraction.
   • Inversion of gradients can be general, affecting all three components: intensity, duration, and spread of the triple downward gradient. In this case, the contraction wave begins in the lower part of the uterus and spreads upward - ascending waves. They are stronger and last longer in the lower part of the uterus than in the upper part and are completely ineffective for dilating the cervix. In some cases, only one or two of the three components are reversible - partial inversion.
   • Uterine uncoordinated contractions are observed in women in labor in whom the contraction wave does not spread throughout the entire uterus (generalized form), but remains localized in a certain area of the uterus. Caldeyro-Barcia distinguishes two degrees of uncoordinated uterine contractions. This is due to the fact that the uterus, according to the author, is functionally divided into numerous zones that contract independently and asynchronously.

Uterine incoordination is characterized by increased uterine tone from 13 to 18 mm Hg, against the background of which small, uneven contractions with a high frequency are superimposed. This so-called uterine fibrillation is also known as "hypertension with hyposystole", "hypertonic form of weakness of labor activity", "essential hypertension". B. Hypertension. Hypertonicity of the uterus, when the tone of the uterus is higher than 12 mm Hg. This anomaly of labor activity is more often observed in complicated labor and is very dangerous for the fetus. The quantitative classification of hypertonicity is as follows - weak hypertonicity - from 12 to 20 mm Hg, moderate - from 20 to 30 mm Hg, strong - over 30 mm Hg. Even up to 60 mm Hg is noted.

Hypertonicity can be caused by 4 completely different factors:

• excessive stretching of the uterus (polyhydramnios), increasing its tone;
• uncoordinated uterine contractions;
• tachysystole of the uterus, when the frequency of contractions exceeds the upper limit - 5 contractions within 10 minutes, and the tone of the uterus rises above 12 mm Hg. With a frequency of contractions of 7 in 10 minutes, an increase in tone to 17 mm Hg is noted. Tachysystole is very dangerous for the fetus, since maternal blood flow through the placenta is greatly reduced, causing asphyxia in the fetus and a decrease in the intensity of uterine contractions;
• an increase in the “basic tone”, the so-called “essential hypertension”.

Hypotonicity of the uterus, when the tone of the uterus is below 8 mm Hg. Caldeyro-Barcia believes that hypotonia during labor is very rare and completely safe. Hypotonicity of the uterus is usually associated with uterine hypoactivity and leads to a slow labor.

3. Cervical dystocia.
   • Passive cervical dystocia caused by cervical fibrosis, cervical atresia, etc.
   • Active cervical dystocia occurs when the triple descending gradient is disrupted (inversion of gradients), leading to spasm of the internal os. It has been shown that even during normal labor, contractions of the lower part of the uterus exert great pressure on the largest circumference of the fetal head, while with a "spastic" uterus this pressure is significantly higher and the dilation of the cervix is slow.

Reynolds (1965) described the patterns of uterine contractile activity (hysterograms) necessary for successful cervical dilation and introduced the concept of the "triple descending uterine gradient" in 1948. The author puts the following idea into this concept: a decrease in the physiological activity of contractions with functional components - the intensity and duration of contractions from the fundus to the lower segment of the uterus. In his monograph, the author provides examples of hysterograms in premature labor, when all three levels (fundus, body, lower segment of the uterus) were active, especially the lower segment of the uterus, and the body gave the greatest irregular activity. In the so-called "false labor" (in our terminology - the pathological preliminary period, according to E. Friedman - the preparatory period), the author noted strong contractions in the uterus, regardless of the location of the sensors on the abdominal wall. There is strong activity of the uterus in the area of its lower segment. There is also a second type of contractions in the pathology indicated, when the lower segment was not active, but there were the strongest contractions in the area of the body of the uterus and the duration of these contractions in it was equal to or exceeded the contractions in the area of the fundus of the uterus. Reynolds called this condition a "physiologic contraction ring". According to the author, prolonged contractions in the area of the lower segment of the uterus are the main reason for the absence of progress in labor, i.e. there is increased activity and a longer duration of uterine contractions in the lower segment of the uterus.

According to the classification of Mosler (1968), based not only on clinical but also on hydrodynamic data, the following are distinguished among the anomalies of labor:

1. hypertensive dystocia (hypertensive dystopia) in the presence of a rigid cervix;
2. hypotensive dystocia.

Later studies showed that abnormal uterine contractions could be identified both in spontaneous labor and during labor induction and labor stimulation with intravenous oxytocin. These abnormalities were usually associated with a decrease in the frequency or decrease in the pauses between contractions, followed by the development of fetal acidosis.

Based on the hysterographic curves, the following classification of labor anomalies is proposed:

• asymmetry of uterine contraction with prolongation of the relaxation phase;
• more than one peak in uterine contraction - polysyle (these contractions resemble "two-humped" contractions);
• double contractions;
• tachysystole with short or no intervals between contractions;
• tachysystole with uterine hypertension;
• uterine tetanus.

Of the modern foreign classifications, the most complete is the classification of H. Jung (1974), which has not only a clinical but also a physiological basis.

The author calls all forms of pathology of labor activity - uterine dystocia. This is explained by the fact that for the normal type of uterine contractions, optimal conditions for the excitation of all myometrium cells with maximum conduction velocity at an equally high excitation threshold of simultaneously included refractory periods of all uterine muscles are necessary. These optimal conditions are not given especially at the beginning of the opening period, and also during labor, according to the author's observations in 20-30% of cases without replacement treatment with agents regulating uterine activity.

The ideal would be to divide the anomalies of labor activity by etiological causes. This experience formed the basis of earlier publications regarding the division of uterine dystopia.

Jung (1967), Caldeyro-Barcia (1958-1960), Cietius (1972) believe that pathology of labor (dystocia) etiologically depends more on the physiological excitation system and to a lesser extent on the energy and working system. I. I. Yakovlev wrote about this back in 1957, that "in a large number of women in labor, the etiopathogenesis of disorders of the contractile activity of the uterus is not fatigue of the smooth muscles, but disorders of the nervous system function."

For clinical purposes, N. Jung proposes the following division of pathological forms of uterine contractile activity:

1. Weakness of labor activity.
2. Hyperactive labor - tachysystole combined with uterine hypertonicity.
3. Hypertensive labor:
   • due to passive stretching of the uterus;
   • essential hypertonic labor;
   • secondary hypertonic labor activity caused by tachysystole.
4. Impaired coordination:
   • excitation gradient disturbance;
   • uncoordinated (uncoordinated) uterine contractions.

At present, only the primary form of weakness of labor activity is of interest, since the secondary weakness of labor activity, which was often described earlier, was explained simply by the depletion of the motor activity of the uterus due to the object of labor, the state of the birth canal.

In case of prolonged labor, one can assume organ fatigue based on the depletion of extracellular energy supply or damage to the transport function of electrolytes in the cell membrane with depletion of extracellular potassium. In such cases, according to Jung, the obstetrician in modern conditions should resort to delivery by cesarean section.

Of the primary forms of weakness of labor activity, often designated in foreign literature as "uterine hypoactivity" or known as "uterine inertia", it is necessary to single out, according to the author, the most frequently occurring type of uterine contractions, physiological, which Cietius called "false labor". In our terminology, we call this condition the normal or pathological preliminary period.

In this predominant pathological variant of labor dysfunction, especially at the beginning of labor, the matter mainly concerns coordination disorder. It is further important to note that at the beginning of labor, each woman in labor can have a transient form of labor weakness. However, labor weakness that persists for a longer time or is observed throughout the entire period of dilation should be attributed to a violation of the transport function of electrolytes in the membrane or a change in cellular metabolism. This also explains the appearance in the literature of reports, taking into account the etiological approach, of the successes of therapy of labor weakness with intravenous infusion of potassium solution and, on the other hand, the successes of treating labor weakness with sparteine (synonym of pachycarpine-d sparteine hydroiodide; Pushpa, Kishoien, 1968). It should be emphasized that sparteine, as well as some other ganglionic blocking agents, has one of the important properties, namely, the ability to increase tone and strengthen contractions of the uterus. In this regard, sparteine was used to enhance labor activity in cases of weak contractions and untimely rupture of water, as well as in cases of weak pushing. The drug is not contraindicated in women in labor who suffer from hypertension, since it does not increase blood pressure.

At present, the method of choice for treating weakness of labor activity is long-term intravenous infusions of oxytocin or prostaglandins. It is important to emphasize that a number of authors consider subcutaneous and intramuscular injections of oxytocin as not giving the desired effect, and their use is currently not justified, although many clinics in the CIS use fractional intramuscular administration of oxytocin, especially in combination with quinine.

Hyperactive labor, according to most authors, is observed only when individual contractions of the uterus during labor indicate an abnormally high amplitude of contractions - more than 50-70 mm Hg when recording intrauterine pressure or if the frequency of contractions during the opening period reaches 4 or more within 10 minutes. In this case, the activity of the uterus in 10 minutes reaches 200-250 Montevideo units. In most cases, there is also an increase in the frequency of contractions with an abnormally high amplitude, explained by the general dependence of both parameters on the membrane potential of the myometrium cell.

It is extremely important to emphasize that isolated tachysystole is observed without a simultaneous increase in amplitude.

Jung points out that hyperactive contractile activity of the uterus is observed as "Wehenstuim" in the case of a threatened rupture of the uterus according to older authors. Such situations arise as a result of endogenous or exogenous overdose of oxytocin. Based on his physiological experiments, the author does not recommend using the concepts known to older authors as "tetanus uteri", since normal contraction of the uterus is already tetanic. What is understood today as "Wehenstuim" (German) or "tetanus uteri" can be explained by a physiologically excitable "Uterus-Kontraktur" through depolarization of the cell membrane.

Equally, cervical dystopia (Dystokie) with insufficient tissue elasticity can reflexively lead to hyperactive labor.

Hypertensive labor is characterized, first of all, by a high resting tone. This anomaly of labor not only prolongs the course of labor, but is also extremely dangerous for the condition of the fetus. H. Jung points out that the old name "hypertonic weakness of labor contractions" should be avoided, based on pathophysiological causes. Obstetricians currently have a more precise idea of the cause of hypertensive labor. Hypertensive labor begins with a resting tone above 12 mm Hg. Studies on the effect of stretching on the electrical and contractile properties of the myometrium have shown that stretching always causes a decrease in the membrane potential of the cells of the cervix and body of the uterus, while the membrane potential of the cells of the body of the uterus is greater than the membrane potential of the cells of the cervix under all hormonal conditions and degrees of stretching. Contractions of the uterus are carried out in the body with the interaction of self-regulation mechanisms and the regulatory influence of the autonomic nervous system. Self-regulatory mechanisms include maintaining optimal excitability, optimal level of polarization of smooth muscle cells and their optimal contractility. Their main elements are the level of hormonal saturation and the degree of stretching of the uterus. The membrane is one of the most important links in the regulatory chain: sex hormones - excitable membrane - contractile elements of myometrium cells. In addition, physiological studies show that stretching of fibers leads to a decrease in membrane potential and thus disruption of the ion exchange process during excitation.

Often, on the basis of a high resting tone, various contractions of smaller amplitudes are associated with disturbances in the rhythm of the contraction order. Continuous stretching of the myometrium, in addition, contributes to a decrease in the threshold and an increase in excitability. Therefore, it is no coincidence that a number of authors in the case of polyhydramnios during pregnancy carry out treatment with amniocentesis with the removal of 1-2 liters of amniotic fluid, very slowly, over 6-12 hours, and with the subsequent administration of beta-adrenergic agents. With this therapeutic measure, the authors achieved a noticeable decrease in resting tone.

Studies have shown that the response of the stretched human myometrium to the impulse of additional stretching is the basis for synchronizing the contractile activity of the smooth muscle cells of the myometrium during labor. The main role here is played by the mechanoreceptor properties of the smooth muscle cells, which respond to any impulse of additional stretching by increasing tension. The increase in tension is proportional to the force of stretching. By labor, connective tissue makes up about 50% of the volume of the myometrium. It was found that the mechanoreceptor properties of the myometrium are due not only to the response of the smooth muscle cells to the impulse of additional stretching, but to a greater extent depend on the elastic properties of the connective tissue framework of the uterus.

Essential hypertonic labor is an active form of muscular hypertonicity of the uterus and such anomaly of labor can soon lead to a decrease in the blood supply to the uterus and thus represents a dangerous form of labor anomaly for the fetus. Another conclusion from this position is important. Long-term increased uterine tone causes myometrium metabolic disorders, leading to painful contractions of the uterus in pregnant women and women in labor.

The result of essential hypertensive labor may be premature detachment of a normally located placenta, most often observed in vegetative dysfunction. In addition, essential hypertension of the uterus may be caused by a reflex release of endogenous oxytocin or a reflex increase in tone based on the "head-neck" reflex identified by Lindgren and Smyth. According to the described reflex, increased stimulation for stretching the cervix through neurogenic afferentation and through the paraventricular nuclei and neurohypophysis can lead to increased release of oxytocin.

Secondary hypertonicity of the uterus is caused by tachysystole. The uterus, due to the early onset of a new contraction with a high frequency, does not have time to fully relax to ensure normal resting tone. A similar picture can be observed with uncoordinated contractions, because the sooner the relaxation phase of a separate contraction is interrupted from subsequent contractions, the higher the forced secondary tone level will be. This does not mean that the height of tone is determined by the frequency of contractions. Physiological experiments by Jung, clinical and hysterographic data from our studies speak against the exclusive unification of secondary hypertonicity through dependence on the frequency of contractions.

Coordination disorders. For effective opening of the cervix and successful completion of labor, a contraction wave with full coordination of various parts of the uterus relative to the time point of its contraction and contractile participation of all myometrium fibers is necessary. Normal labor is carried out with maximum intensity and duration of contractions in the bottom of the uterus, the so-called "triple descending gradient" of uterine contractions according to Reynolds, Caldeyro-Baicia. Disturbances in general coordination or individual elements of the "triple descending gradient" can lead to multiple pathological forms of contractions, which can slow down labor to a greater or lesser extent.

There are two types of arousal gradient disturbances that deviate from the physiological course of uterine contractions. The first type of arousal gradient disturbance is manifested by the fact that contractions in the lower segment of the uterus are stronger and longer than in its bottom. The other type is when the contraction waves have an increasing or widening spread. There are statements in the literature that both of these types of arousal gradient disturbances lead to a slow opening of the cervix during labor, since the normal retraction of the muscles in the bottom of the uterus is disrupted.

Some clinicians note the so-called secondary weakness of labor activity when the cervix opens to 6-8 cm, associating it with the fairly frequent formation of a "lock" of the cervix during this opening simultaneously with contractions. They consider the loss of the locking function of the cervical muscles to be one of the important links in the prenatal restructuring of the myometrium. The function of this part of the uterus is of great importance for maintaining pregnancy and the physiological course of labor. Many obstetricians call the process of losing the locking function of the cervical muscle "maturation of the cervix". N. S. Baksheev believes that this term is inappropriate and does not reflect the physiological essence of this process. Lindgren's studies have shown that such hypertonicity of the uterus in its lower segment ("lock") is observed in 1-2% of women in labor and can be eliminated in the case of a slow course of labor by using inhalation agents from the halogen-containing group (fluorothane). Some authors, in such an obstetric situation and dilation of the uterine os by 8 cm or more, recommend digital dilation of the uterine os with subsequent surgical delivery - vacuum extraction of the fetus against the background of barbiturate-fluorothane (halothane) anesthesia. It is equally important to emphasize the great difficulty of making a correct diagnosis by an obstetrician when determining a violation of the contraction gradient, since even the use of internal hysterography with determination of the magnitude of intra-uterine pressure in this obstetric situation is not indicative.

Undoubtedly, in pathological forms of labor contractions, especially at the beginning of the dilation period, the violation of contraction coordination is of particular importance.

During normal labor, the wave of contractions spreads, covering all parts of the uterus from the "pace-maker", which is predominantly located in the left tubal angle of the uterine fundus down through the entire uterus. However, there are typical disturbances in the conditions of excitation and local differences in excitability, the consequence of which are contractions independent of each other in different parts of the uterus, both in place and time of their occurrence. In this case, some contractions may originate from the "pace-maker", prevailing in the left tubal angle. However, they may be detected due to numerous potentially excitable foci of the myometrium in any other parts of the myometrium.

When explaining various clinical and hysterographic pictures, it is necessary to know that the disruption of the coordination of uterine contractions can occur with the participation of two different excitation centers. All other variants of disruption of coordination should be considered between the form described above and independent multiple excitation and contraction centers. In this case, the evoked bioelectrical activity in 60% of cases is accompanied by local contraction, and in 40 % it spreads according to the pacemaker type.

This form is clinically manifested as very frequent contractions with small local amplitudes. In most of such uncoordinated centers, labor contractions are referred to by some authors as "muscle flickering" ("muscle-flimraern"). The normal progress of labor is known to be significantly disrupted when coordination is impaired. However, clinicians are well aware of cases where a woman often spontaneously delivers without regulating therapy. Jung's work provides a hysterogram showing a picture between the main rhythm of contractions and a subordinate, secondary rhythm from another excitation center. In this case, excitation from the primary main rhythm passes into the refractory phase of the secondary rhythm. Upon detailed examination of the hysterographic pictures, it can be seen that the main rhythm runs parallel to the contraction intervals of the secondary rhythm. It is clear that such a course of labor with an optimal frequency of contractions and their amplitudes, even despite the presence of smaller rhythm disturbances, can give a picture of a "normal" period of dilation. That is why in recent years the issue of introducing cardiac monitoring and hysterographic monitoring into clinical obstetric practice during normal and particularly complicated labor has been widely discussed.

The causes of disturbances in the contractile activity of the uterus may be:

• excessive nervous and mental stress, negative emotions;
• failure of neurohumoral mechanisms regulating labor activity due to acute and chronic infectious diseases, diseases of the nervous system, and disorders of lipid metabolism;
• developmental anomalies and tumors of the uterus (saddle-shaped, unicornuate, septum in the uterus, uterine myoma, etc.);
• pathological changes in the cervix and body of the uterus;
• the presence of a mechanical obstacle to the advancement of the fetus (narrow pelvis, tumors, etc.);
• polyhydramnios, multiple pregnancy, oligohydramnios;
• post-term pregnancy;
• irrational use of uterotonic drugs.

The group of pregnant women at “high risk” of developing labor anomalies should include patients with:

• frequent acute infectious diseases in childhood and adulthood;
• chronic infectious and allergic diseases (chronic tonsillitis, pyelonephritis, etc.);
• late and early onset of menarche;
• menstrual dysfunction;
• general and genital infantilism;
• disorders of the reproductive function (history of infertility);
• history of abortions;
• inflammatory diseases of the genital organs;
• endocrinopathies, disorders of lipid metabolism (especially obesity of III-IV degree);
• complicated course of previous births (abnormalities of labor, etc.);
• complicated course of the current pregnancy (threat of miscarriage, toxicosis, frequent intercurrent diseases);
• bottom location of the placenta;
• the age of the first-time mother is up to 19 and over 30 years;
• absence of signs of readiness of the pregnant woman’s body for childbirth (immaturity of the cervix, negative oxytocin test, etc.).

Classification of anomalies of labor activity [Chernukha E.A. et al., 1990]

1. Pathological preliminary period.
2. Weakness of labor activity (hypoactivity or inertia of the uterus):
   • primary;
   • secondary;
   • weakness of pushing (primary, secondary).
3. Excessively strong labor activity (uterine hyperactivity).
4. Coordinated labor:
   • discoordination;
   • hypertonicity of the lower segment of the uterus (reverse gradient);
   • circular dystocia (contraction ring);
   • convulsive contractions (uterine tetany).