What is the anomaly of labor?

Anomalies of labor activity - an urgent problem of modern scientific and practical obstetrics. The importance of this issue is due primarily to the fact that this pathology is one of the main causes of serious complications in both the mother and the child. It is important to note that for all biological systems, not only the genetic continuity of its components and the definiteness of the structure are characteristic, but also the known stability-the ability to maintain and restore this structure in its infringements, ie, the ability to regulate.

All regulatory processes are carried out at the expense of forces acting within the system. Consequently, biological regulation is always self-regulation.

Biological systems - a cell, a multicellular organism, a population, a race, a species, a subspecies - form a single series of interrelated, hierarchically subordinate units.

From the position of the theory of regulation of biological systems, it is believed that living organisms (being open systems) could not survive in a changing environment if they were managed only by homeostatic mechanisms. There is a higher level of regulation, coupled with motivations, behavioral manifestations, this organismic level of regulation can significantly modulate hierarchically subordinate systems and the level of adjustment of regulated systems.

The legality of this kind of processes also applies to the generic act - a complex physiological multi-link process that occurs and terminates as a result of the interaction of many body systems. However, a number of authors deny the role of the central nervous system in the regulation of the generic act. N. Knaus (1968), in an article on the causes of the onset of labor, summarizing his fifty years of scientific work on the causes of the onset of labor, proposing his own theory of hypertrophy of the uterus musculature and its electrophysiological characteristics, concludes by pointing out that "the onset of labor in man occurs only in the uterus and has no external hormonal effects. "

In our time, a number of clinicians and physiologists emphasize the idea that among the smooth muscle organs the uterus occupies an exceptional place due to a special function, differences in structure and response to various environmental factors. To understand the characteristics of contractile activity of the uterus, it is necessary to know the structure, the mechanism of excitation and contraction of individual cells, the processes of cellular self-regulation. Since the number of active factors on the myometrium is large, it is first of all necessary to find the general principles underlying the activity of myometrium cells.

Spontaneous uterine activity is of interest. In the emergence of spontaneous electrical activity of the uterus, the presence of groups of active cells, the so-called rhythm drivers of myogenic nature (pacemaker cells), can play a role, their excitation is transmitted through intercellular pathways. According to the well-known researcher Marshall, pacemaker potentials are found in all parts of the myometrium and, therefore, the region of spontaneous potential generation is not localized in special parts of the uterus, but can move inside the tissue.

Alvarez, Caldeyro-Barcia have established two types of abbreviations:

• I type - "rhythmic reduction of low intensity" from 1 to 3 cuts per minute in all pregnant women, from the 9th week of pregnancy to the period of birth;
• II type - "non-rhythmic contractions of high intensity" - they are felt palpation, and the most pregnant woman in the form of densification (tension) of the uterus; appear sporadically, without a certain rhythm until the last 2 weeks before the onset of labor (before the 38th week of pregnancy).

According to some authors, in muscle cells the healthy body's myometrium from the moment of puberty manifests itself a self-excited system, determined by the ratio of sex hormones and biologically active substances responsible for organizing the ion equilibrium of the relative rest potential and action potentials. The patterns of manifestation of electrophysiological properties are determined in the cell's gene apparatus and are standard for certain body conditions. The authors in experimental studies have shown that even in conditions of saturation of the body with progesterone, the development of contraction and the exercise of normal births are possible.

It is important to emphasize that the difference in the membrane potential of the cervical and uterine body cells can explain the different behavior of these parts in labor; in the mechanism of regulation of labor, coordination of functions of different parts of the uterus, the cellular membrane mechanism plays an important role.

In explaining the factors contributing to the onset of labor, these authors believe that the physiological analysis of the contractile activity of the uterus during labor gives reason to believe that the contraction of myometrium muscle cells in labor is not a new phenomenon for this organ, but characterizes the restoration of the natural properties of these structures temporarily suppressed by pregnancy factors . The inhibition of the contractile function of the cells of the myometrium involves a gradual, step-by-step removal of the inhibitory factors and the restoration of the natural function of this organ.

A characteristic feature of physiological genera is the increase in the dynamics of uterine contraction and the opening of its neck with a very clear spontaneous autoregulation of this process. The birth, i.e., the process of spontaneously arising contractions of the uterine muscle with a self-regulating system of this function, takes place provided the body is ready to develop this process.

Some authors, who recognized the role of the nervous system in the generic act, explained the onset of the birth act by the fact that the present part irritates the ganglion cervicale and thus causes fights. Omitting the present part irritates the new nerve elements, making the fights even more intense. The more new nervous elements are included, the stronger their irritation and the stronger the contractions become. When the head is at the bottom of the pelvis, contractions reach the highest strength, because at this time in a state of excitement are all the nerve elements of the pelvis. These complex dynamic relationships are expressed in the works of modern researchers. NS Baksheev also points out that mechanical stretching of the cervical and vaginal tissues intensifies contraction. It is indicated that the tension of the fetal bladder in the region of the cervical canal and the passage of the presenting part through these genital organs stimulates the contraction of the myometrium.

The stimulation mechanism can include the effect on the hypothalamus through the uterus mechanoreceptors along the conduction pathways of the spinal cord, in particular, to activate neurons in paraventricular nuclei that control the release of oxytocin from the posterior lobe of the pituitary gland. The amniotic fluid, together with the membranes of the fetal egg, significantly affects the correct course of the opening period. Its action is twofold: dynamic and purely mechanical.

Dynamic action, according to A. Ya. Klassovsky, is expressed in the fact that the fetal bladder, in contact with the lower segment of the uterus, greatly enhances uterine contractions by a reflex path, thus facilitating the opening of the uterine throat. Mechanical - is that with the appearance of birth fights, the lower part of it with the help of the amniotic fluid first exerts pressure on the lower segment of the uterus, and by stretching it enters the uterine pharynx and, passing like a wedge, facilitates its opening. With the outflow of water, uterine contractions are usually intensified and acceleration of the normal course of labor is noted. The author emphasized that the premature discharge of amniotic fluid, although it enhances uterine contractions, but the contractions acquire an incorrect character.

In a number of detailed recent works, the unfavorable effect of early opening of the membranes with the goal of rhodoconstriction is described. According to Caldeyro-Barcia, early amniotomy is very common in Europe and Latin America. At 26,000 births with a spontaneous onset of labor, an early amniotomy was performed in 20%. According to Niswander, Schwarz, the rupture of the bladder has an adverse effect on childbirth and the condition of the fetus and newborn baby. It is believed that the artificial rupture of membranes at an early stage of childbirth from a scientific point of view is not justified.

To date, there is no convincing data on the responsibility of the cerebral cortex or subcortical structures of vegetative centers for the trigger mechanism of labor. The authors believe that the birth act is hereditarily determined and conditioned by the genetic apparatus of the female body and fetus, under normal course always manifests itself by a definite complex of uterine reactions and functional systems of the parturient woman. At the same time, a total reduction in all smooth muscle cells or most of them (labor contraction) occurs when the ratio between estrogens and progesterone reaches the optimal level that ensures self-excitation, synchronism of cell contraction, and a high degree of coordination of reactions to substances of uterotonic action.

When studying the physiology and the clinic of hormonal regulation of the uterus, all biological processes in the uterus are divided into 2 kinds of functions that depend on each other:

• "Working system" - is responsible for the quantitative and qualitative layout of the contractile ability of myofibrils and proteins (structures), an area largely occupied by biochemists;
• the functional circle of the "excitation system" is an intermediary-distributor or consumer with respect to the contractile activity of proteins.

N. Jung in experimental studies carried out in situ and in vitro on white Wistar rats, as well as cats and rabbits, on the strips of human uterine myometrium obtained from pregnant women showed a tonic and phase double principle of uterine contraction. As is known, during pregnancy, the uterine mass increases from 50 g to 1000 g. The increase in the volume and mass of the uterus is associated mainly with its hypertrophy and hyperplasia. However, only H.Knaus raised the question that a large increase in muscle power during pregnancy, which can be achieved by 15-20-fold increase in each individual muscle cell, can be considered as the cause of the onset of labor. In the electrophysiological studies of Csapo, Larks, Jung, and other authors, the focus was also on the function of the cell membrane, neglecting the progression of the uterus musculature during pregnancy. According to N. Knaus, this apparent hypertrophy of the musculature of the uterus is caused only by estrogen of the placenta, and not by progesterone. And the author for forty years in a number of works has proved this, since the functionally significant hypertrophy increases before the placenta is rejected. This fact, according to the author, can be explained as follows: first of all, accurate tracking of the increase in the mass of the pregnant uterus of a man to the end of pregnancy has a number of difficulties, since it is hardly possible to weigh pregnant mothers by months, and, in addition, the growth of the pregnant uterus influence of the size of the fetus and its placenta. However, to resolve this issue, there is an experimentally satisfying method - the use of a sterile uterus with unilateral pregnancy in a rabbit (in one horn). Under these conditions, the empty horn used for mass control remains unchanged, in contrast to the mass and size of the fetus in the pregnant horn. Thanks to the stimulation of the estrogen introduced into the blood, the empty horn grows in the same way as the human uterus under the hormonal influence of the egg in the tube. By excluding the local effect of the egg on the uterus during pregnancy in one horn in a rabbit, it can be established that an empty horn from the 8th to the 10th, The first day of pregnancy begins to grow and that the increase in weight before the onset of labor is delayed. Thanks to these ideal methodical methods, the author was able to prove that the hypertrophy of the uterus muscles during pregnancy progresses as long as there is a stimulating growth due to the estrogen effect, and with the placenta rejection, the uterine hypertrophy ceases. Hypertrophy increases before the onset of labor, which is an easily understood consequence, increasing before the onset of delivery, by the release of estrogens through the placenta, as evidenced by numerous systematic studies. However, Knaus emphasizes the idea that estrogens in their action on the uterus, or more precisely its myometrium, are a growth hormone, rather than a stimulant for labor, so it can not be expected that with their help in the uterus in vivo or in vitro, direct amplification can be achieved her motor skills after their application, which completely coincides with clinical observations.

It is believed that the rate of excitation power, which in turn determines the strength of the muscular function, depends on the cross section and the length of the muscle fiber, thereby from the upper surface of the cell, which affects the capacity of the membrane potential for the excitation state; the conductivity resistance of the membrane, which also reflects the state of excitation of the membrane potential, conductivity resistance and membrane resistance, as well as the penetration of sodium into the cell. Of these factors, which significantly affect the degree of contractility of the uterine muscle (its power), the size of the increase in myometrium cells is known to be 15-20 times, but many other factors and parameters of their change are unknown, which also affect the rate of conduction of excitation in muscle of the uterus as pregnancy progresses due to increasing uterine hypertrophy, and physiologically explain the ongoing transition of existing permanent strengths during pregnancy to a regular labor awns.

Thus, by recognizing the functional significance of powerful uterine hypertrophy during pregnancy and indicating the result of 1000-fold acceleration in the initiation of contractile elements, the problem of the onset of labor, in the opinion of Knaus, has been solved for humans. As a clinical proof, the author cites the procedure for the onset of labor in Drew-Smythe (1931), when using an S-shaped conductor 35 cm long produces an almost complete removal of amniotic fluid, thereby shortening the myometrium fiber and thereby increasing the cell cross-section. Since the rate of excitation depends on the diameter of the fiber, it is easy enough to explain the electrophysiological clinical effect in the appearance of uterine contractions in the clinic.

An important in the activity of myometrium cells is the autoregulatory mechanoreceptor membrane mechanism. Myometrium cells combine the properties of the contractile and receptor systems.

The morphological structure of the uterus is such that the main volume in the myometrium is occupied by connective tissue, and the smooth muscle cells are included in it in small layers. Therefore, even with a strong stretching of the uterus that takes place at the end of pregnancy, the connective tissue network, apparently, protects the smooth muscle cells from overexertion, so that they retain mechanoreceptor properties. The main functional significance of the mechanoreceptor mechanism, it seems to the authors, is to create optimal conditions for the generation of action potentials, since the moderate stretching applied to the smooth muscle cells causes the depolarization of their membranes, the generation of action potentials and contraction. It is impossible to exclude and other ways of influence of long stretching. Deformation of the cell membrane can lead to an increase in ionic permeability, activate the transfer of ions through intracellular structures and directly affect the contractile proteins of cells.

From these data it can be seen that the requirement to ensure high reliability and automatism of the function led to the creation during the evolution of some specific mechanisms of self-regulation that distinguish the behavior of myometrium cells from all other cells of smooth muscle and heart.