Prolonged latent labor phase

The latent phase of labor is the time between the onset of labor and the onset of the active phase (the rise of the curve indicating the opening of the cervix). The average duration of the latent phase in primiparous women is 8.6 hours, in multiparous women - 5.3 hours.

A prolonged latent phase can be considered in cases where its duration is 20 hours in primiparous women and 14 hours in multiparous women.

Diagnosis is complicated by the timing of the onset of labor and the onset of the active phase. In many cases, it is difficult to distinguish between false labor and the latent phase of labor. In addition, it is sometimes difficult to decide whether it is a prolonged latent phase or an early secondary arrest of cervical dilation.

The problem of differential diagnosis between the latent phase of labor and false labor does not play a decisive role as long as the obstetrician avoids such active interventions as amniotomy or stimulation of labor. Expectant management does not harm either the child or the mother. In contrast, intervention can lead to a number of complications and, consequently, to perinatal and maternal morbidity.

The most adequate sign of the onset of labor should be considered the smoothing and opening of the cervix.

More important is the differential diagnosis between a prolonged latent phase and early secondary arrest of cervical dilation. The former condition is not dangerous, while the latter is associated with a significant risk of fetal pelvic mismatch. There are usually no problems with diagnosis if the pregnant woman was observed for several hours in the maternity hospital, as a result of which a clear rise in the cervical dilation curve was recorded. Problems usually arise in cases where pregnant women are admitted with a cervix dilated by 3-4 cm, with pronounced smoothing of the cervix, regular contractions, but no further dilation occurs over the next few hours. These pregnant women may have secondary arrest of cervical dilation or a prolonged latent phase. Since differential diagnosis is impossible under such circumstances, it is best to assume the worst (secondary cessation of cervical dilation) and begin the necessary diagnostic and therapeutic measures.

Frequency: A prolonged latent phase is observed in 1.45% of primiparous women and 0.33% of multiparous women.

Causes. The most common etiologic factor (about 50% of cases) causing a prolonged latent phase in primiparous women is the early and excessive use of sedatives and painkillers during labor. In such cases, the restoration of normal labor usually occurs after the effect of these drugs has ceased. The second reason for the development of complications in primiparous women is the insufficient maturity of the cervix at the beginning of labor. The cervix remains dense, unsmoothed, and unopened.

The most common cause of a prolonged latent phase in women who have given birth for the first time is the development of false labor. If they are observed in approximately 10% of primiparous women with an initial diagnosis of a prolonged latent phase, then in multiparous women with the same diagnosis they are observed in more than 50% of cases. The difference in the frequency of false labor indicates how difficult it is to establish the onset of labor in women who have given birth for the first time.

In 75% of women in labor with this anomaly, normal labor continues after the latent phase, ending in normal labor. In a smaller number of women, after the protracted latent phase, another anomaly develops - secondary cessation of cervical dilation (in 6.9% of women in labor) or a prolonged active phase (in 20.6%). If other labor anomalies are present, the prognosis is unfavorable, since a cesarean section is required quite often (in about 100% of cases). Finally, false labor occurs in approximately 10% of women in labor with a protracted latent phase.

Management of labor during a prolonged latent phase of labor

There are two approaches to managing pregnant women with a prolonged latent phase: 1) maintaining rest and 2) stimulating labor with oxytocin. Both methods provide approximately the same results, helping to eliminate existing labor disorders in approximately 85% of cases.

When choosing a method of management, it is necessary to take into account the degree of fatigue and anxiety of the woman in labor, the main cause of this complication (overdose of sedatives, immature cervix), as well as the preference for using one or another method for both the mother and the obstetrician.

If it is decided to choose the method of management of rest (therapeutic sleep), the pregnant woman should be administered 0.015 g of morphine intramuscularly, followed by the administration of secobarbital.

Morphine. Extensive experience in the clinical use of morphine has shown that the drug has undoubted advantages. Morphine provides deep pain relief without amnesia, does not cause myocardial sensitization to catecholamines, does not disrupt blood flow and its regulation in the brain, heart, kidneys, and has no toxic effect on the liver, kidneys, and other organs. Intramuscular and subcutaneous administration of morphine provides the optimal duration of its action, while after its intravenous administration, the half-life (T _1/2 ) is only about 100 minutes. Morphine partially binds to plasma proteins. The threshold analgesic effect of the drug develops at a concentration of free morphine in the blood plasma of 30 ng / ml. Morphine is excreted from the body mainly through the kidneys, mainly in the form of glucuronide. Experiments have shown that the activity of morphine can change 7 times depending on the time of day and the phase of the menstrual cycle.

Morphine and other morphine-like drugs can cross the placenta. It has been found that after intramuscular administration of 2 mg morphine per 10 kg of body weight to the mother, the ratio of drug concentrations in the fetus to the mother increases over approximately 1/2 hour. In the mother, the maximum concentration of morphine in the blood plasma was reached 1 hour after this injection. Morphine penetrates into breast milk only in small quantities, and at therapeutic doses they do not have a significant effect on the child.

Promedolis a domestic synthetic analogue of meperidine, 5-6 times less active than morphine, with various methods of administration. Promedol is safer for the fetus. But it should be remembered that after the introduction of promedol (meperidine) during labor, the fetus may develop harmful effects, depending on the time of administration of the drug to the mother. Therefore, during labor, narcotic analgesics should be administered only in the first half of the first stage of labor or if the child is due to be born within the next hour. Moreover, promedol has some labor-stimulating effect, has a beneficial effect on blood circulation in the pregnant uterus, which allows it to be considered as a drug of choice in an obstetric clinic.

Secobarbital sodium (Seconal) is a short-acting barbiturate. A single dose of 100-200 mg of the drug produces a hypnotic effect. It is available as 100 mg tablets, 4 mg/ml elixir, and 250 mg injections. Secobarbital produces a short-acting hypnotic effect (less than 4 hours).

Treatment with these drugs is effective: the vast majority of women fall asleep within 1 hour after its onset and wake up 4-5 hours later with active labor or without any signs of it. This may occur due to opioid inhibition of oxytocin release from the posterior pituitary gland under the influence of opiates similar to morphine and opioid peptides - beta-endorphin and enkephalin analogues.

There is a risk of two potential problems with this treatment. The first is the mistaken prescription of a large dose of narcotic drugs to a woman already in active labor, who may give birth to a child with signs of suppression of vital functions shortly after treatment. To avoid this, it is necessary to carefully assess the state of labor before prescribing drug therapy. If this does happen, the pediatrician should be warned before the birth so that he or she can be prepared to begin appropriate treatment of the newborn if necessary.

The second problem is the administration of small doses of drugs, which are often ineffective and worsen the course of the existing complication. The doses recommended above are adequate for most women and can be reduced only in women of short stature and low body weight. In women of greater weight, the dose of morphine can reach 20 mg subcutaneously. If uterine contractions are observed 20 minutes after the administration of morphine, it is necessary to additionally administer 10 mg, and in case of excess weight of the woman in labor - 15 mg of morphine.

When deciding to start labor stimulation with oxytocin, it is administered intravenously by drip; labor should be monitored. If labor has already begun, large doses of the drug may not be required to initiate the active phase. Oxytocin should be administered starting with 0.5-1.0 mIU/min, gradually increasing the dose at 20-30 minute intervals. In most women in labor with a latent phase of labor, the effect is observed with oxytocin doses not exceeding 8 mIU/min. It is recommended to dilute 10 U of oxytocin in 1000 ml of 5% dextrose solution. Administration should be performed using a special perfuer, gradually increasing the dose every 20 minutes until adequate labor develops.

A therapeutic error that should be avoided in the case of a prolonged latent phase is the opening of the amniotic sac in order to accelerate labor. According to E. Friedman (1978), amniotomy is not successful in this case.

In addition, since the prognosis for a prolonged latent phase is quite favorable and treatment of this disorder is usually successful, performing a cesarean section in such cases is not justified unless there are other indications other than an anomaly of labor. There is no common sense in performing a cesarean section in a prolonged latent phase.

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