Weakness of labor (hypoactivity, or inertness of the uterus)

Weakness of labor is a condition in which the intensity, duration and frequency of contractions are insufficient, and therefore smoothing the cervix, opening the cervical canal and moving the fetus, when it corresponds to the pelvic size, is slow.

There are primary and secondary weakness of labor. The primary weakness of labor is called arising from the beginning of childbirth and continuing during the period of disclosure and until the end of labor. The weakness of labor that occurs after a period of prolonged good labor activity and manifests itself in the characteristic features of the above is called secondary.

Weakness of attempts (primary or secondary) is characterized by their insufficiency due to weakness of abdominal muscles or fatigue. In practical obstetrics, the weakness of attempts is attributed to the secondary weakness of labor.

The frequency of weakness of labor is about 10%. Often, prolonged labor, due to other abnormalities of labor, is unreasonably attributed to weakness.

The primary weakness of labor can arise as a result of insufficiency of the impulses that cause, support and regulate labor, and inability of the uterus to perceive or respond with sufficient contractions to these impulses.

In the pathogenesis of the weakness of labor, an important role is played by a decrease in the level of estrogen saturation, a violation of the synthesis of prostaglandins, protein (hypoproteinemia), carbohydrate, lipid and mineral metabolism, low levels of enzymes of the pentose phosphate cycle of carbohydrates.

Among the anomalies of labor activity, the weakness of labor activity has been most studied.

At present, the weakness of labor activity tends to increase from 7.09% to 12.21%.

The specific gravity of the primary weakness of labor activity in relation to the secondary has changed. It was revealed that the primary weakness of labor is 55% of the total number of cases.

A number of authors note a greater frequency of weakness in labor activity in primiparas as compared to those of moles. Ye. T. Mikhaylenko believes that the weakness of labor activity in primiparas occurs 4.4 times more often than in the parasites.

In the frequency of occurrence of weakness of labor activity, the age of parturient women plays an important role.

As early as 1902, VA Petrov wrote that it is more common in young primigravidae (16-17 years) and in women older than 25-26 years. According to modern authors, this pathology is more common at a young age - 20-25 years. Weakness of labor is more common in young parturient women and in primiparous over 30 years. It is significant that the violation of contractile activity of the uterus is observed in women giving birth at the age of over 30 years 4 times more often than at a younger age.

Primary weakness of labor

The clinical picture of childbirth with the primary weakness of the ancestral forces is diverse. Contractions can be very rare, but of satisfactory strength; fairly frequent, but weak and short. The more favorable are the rare and satisfactory strength of the fight, since long pauses contribute to the relaxation of the uterine musculature. Smoothness of the cervix and opening of the uterine throat are slowed down, which is clearly visible when conducting the partograph.

With the primary weakness of labor, the present portion remains mobile for a long time, or pressed against the entrance to the small pelvis, when it corresponds to the pelvic dimensions. The duration of childbirth sharply increases, which leads to fatigue in the parturient woman. Often there is an untimely outflow of amniotic fluid, and this contributes to the lengthening of the anhydrous gap, the infection of the mother and the suffering of the fetus.

Prolonged immovable standing of the presenting part in one of the planes of the small pelvis, accompanied by compression and anemization of soft tissues, can lead to the subsequent occurrence of urogenital and intestinal fistula.

In the postpartum period, hypotonic bleeding is often observed, as a result of decreased uterine contractility, as well as delay in the uterus of the placenta and its parts; After the birth of the afterbirth, halo- or atonic bleeding is observed for the same reason. In the postpartum period, inflammatory diseases often occur.

Diagnosis of weakness of labor is established on the basis of:

• insufficient uterine activity;
• slowed speed of smoothing of the cervix and opening of the uterine throat;
• prolonged standing of the presenting part in the pelvic inlet and slow motion in accordance with the pelvic dimensions;
• increased duration of labor;
• fatigue of the mother in childbirth and often intrauterine fetal suffering.

Diagnosis of the weakness of labor should be set with a dynamic observation of the woman in labor for 2-3 hours. With monitoring, the diagnosis can be established after 1-2 hours. In a differential relation, it is important to exclude the pathological preliminaries, cervical dystopia, discordant generic activity, clinical mismatch between the size of the pelvis and the head of the fetus.

Thus, the main clinical manifestation of the weakness of labor is lengthening the duration of labor. However, up to the present time in the literature there are contradictory data on the duration of both normal delivery and labor, complicated by the weakness of labor. In particular, according to research, the average duration of normal labor is 6 hours, with weakness of labor activity it increases to 24 hours and even up to 30 hours.

According to the data, the duration of normal labor is 6-12 hours, in primiparas they can extend up to 24 hours.

According to the data of modern authors, the total length of labor with a physiological course is 16-18 hours in primiparas, 12-14 hours in re-births.

The duration of labor with the primary weakness of labor is 33 h 15 min in primiparas and 20 h 20 min in re-parenting.

The duration of labor with a secondary weakness of labor is 36 hours in primiparas and 24 hours in re-parenting.

TA Starostina (1977) proposed a classification of the weakness of labor activity, depending on the length of labor. The author distinguishes three degrees of weakness of labor: I - up to 19 hours; II - from 19 to 24 hours and III - over 24 hours.

Clinical characteristics of the course of labor are given on the basis of palpatory evaluation of contractile activity of the uterus (intensity and duration of fights, their frequency, duration of the interval between contractions), dynamics of opening of the uterine throat and fetal movement through the birth canal. According to NS Baksheev (1972), the duration of an effective contraction, determined palpatory, from the onset of contraction to the beginning of relaxation of the uterus is 35-60 seconds. One fight should not occur more than 3-4 minutes. More frequent and less prolonged contractions are ineffective.

With primary weakness of labor, fights are frequent, prolonged, but weak; the opening of the uterine throat is very slow. According LS Persianinova (1975), the most unfavorable fights weak, short-term and irregular, up to the complete cessation of contractile activity of the uterus.

An important criterion for the clinical course of labor is the rate of cervical dilatation. According to LS Persianinov (1964), if from the onset of labor 12 hours have passed in the primiparous and 6 hours in the re-birth and there is no opening of the uterine throat to three fingers (6 cm), in this case there is a weakness in the labor. It is believed that in the normal course of labor the opening of the cervix of the uterus by 8-10 cm takes place during 10-12 hours of labor, while the weakness of labor activity during the same time, the uterine zoe opens up to 2-4 cm, rarely - 5 cm.

Fatigue of the musculature of the uterus, a violation of its motor function in case of weakness in labor activity is one of the main causes of various complications of childbirth, postpartum and postnatal periods, as well as the negative impact on the body of the mother, fetus and newborn. There is a high frequency of untimely passage of amniotic fluid with weakness of labor activity from 27.5% to 63.01%. In 24-26% of women giving birth, the frequency of surgical interventions increases (obstetrical forceps, vacuum extraction of the fetus, cesarean section, fruit-destroying operations).

With the weakness of labor, pathological hemorrhages in the consecutive and early postpartum periods are much more frequent: more than 400 ml in 34.7-50.7% of parturient women. Weakness of labor is one of the causes of postpartum diseases. With an anhydrous interval of up to 6 hours, postpartum diseases occur in 5.84%, 6-12 hours in 6.82%, 12-20 hours in 11.96% and more than 20 hours in 41.4% of cases.

Secondary weakness of labor

Secondary weakness of labor is most often observed at the end of the period of cervical dilatation and in the period of exile. This anomaly of labor is found in about 2.4% of the total number of births.

The causes of the secondary weakness of labor are varied. Factors leading to the primary weakness of labor can lead to a secondary weakness in labor activity, if they are less pronounced and show their negative effect only at the end of the period of disclosure and in the period of exile.

The secondary weakness of labor is most often noted as a result of a significant obstacle to delivery with:

• clinically narrow pelvis;
• hydrocephalus;
• incorrect insertions of the head;
• transverse and oblique position of the fetus;
• obstinate tissues of the birth canal (immaturity and rigidity of the cervix, its cicatricial changes);
• stenosis of the vagina;
• tumors in the small pelvis;
• pelvic presentation;
• pronounced soreness of fights and attempts;
• untimely opening of the fetal bladder due to excessive density of the membranes;
• endometritis;
• inept and disorderly use of uterotonic drugs, antispasmodics, analgesics and other means.

Symptoms of secondary weakness of labor are characterized by an increase in the duration of the birth act, mainly due to the period of exile. Contractions that were initially intense enough, long and rhythmic, become weaker and shorter, and pauses between them increase. In a number of cases, contractions almost cease. The movement of the fetus along the ancestral canal slows down or stops. Childbirth takes a protracted character, leading to fatigue in the parturient woman, which may contribute to the onset of endometritis in childbirth, hypoxia and fetal death.

Diagnostics. The diagnosis of secondary weakness of labor is based on the given clinical picture, and objective methods of its registration (hystero- and cardiotocography) in the dynamics of labor provide a great help.

To resolve the issue of medical tactics, it is necessary to try to establish the cause of secondary weakness.

It is very important to differentiate the secondary weakness of labor with a clinical mismatch between the size of the pelvis and the fetal head.

Conduction of labor with secondary ancestral weakness

The question of medical tactics is decided after determining the cause of the secondary weakness of labor. Thus, with the secondary weakness of labor activity due to excessive density of shells, their immediate dissection is shown. It is very important to differentiate the secondary weakness of labor with a clinical mismatch between the size of the pelvis and the fetal head.

The best way to combat the secondary weakness of labor in the first period of labor is to provide rest for the woman in labor (electroanalgesia, GHB); after awakening to follow the nature of labor activity within 1-1 % h and in case of its insufficiency rhodostimulation by one of the above means (oxytocin, prostaglandin) is indicated. It is necessary to introduce antispasmodic and analgesic drugs, to prevent fetal hypoxia. In the period of exile, with a head standing in a narrow part of the pelvic cavity or in the outlet, inject oxytocin (0.2 ml under the skin) or give a tablet of oxytocin (25 U) per cheek.

In the absence of the effect of conservative measures, operative delivery (imposition of obstetric forceps, vacuum extractor, extraction of the fetus behind the pelvic end, etc.) is shown, depending on the available conditions, without waiting for signs of acute fetal hypoxia, for in such cases the operation will be more traumatic for the suffering fetus.

If the movement of the head located on the pelvic floor is delayed due to the rigid or high perineum, perineo or episiotomy should be performed.

With the secondary weakness of labor activity in combination with other unfavorable factors and the lack of conditions for delivery through the natural birth canal, a caesarean section should be performed. In the presence of infection in parturient women, the method of choice is an extraperitoneal Caesarean section or a cesarean section with a temporary delimitation of the abdominal cavity.

In the case of signs of developing infection, as well as anhydrous interval more than 12 hours, if the end of labor is not expected in the nearest 1-1 % h, antibiotics (ampicillin, ampiox, etc.) are indicated.

To prevent bleeding in the consecutive and early postpartum periods, the introduction of uterotonic drugs (methelergometrin, oxytocin, prostaglandin) is necessary.