Obstetrics and Gynecology - A.M. Gromova 2000

Uterine Contractility Disorders
Classification of Labor Anomalies
Uterine Inertia (Hypoactivity or Uterine Atony)

This is a condition characterized by insufficient intensity, duration, and frequency of uterine contractions, resulting in a slowed progression of cervical effacement, cervical dilation, and fetal descent, despite a normal proportion between the fetus and the maternal pelvis.

Primary uterine inertia occurs from the very onset of labor and may persist throughout the dilation stage and until the completion of delivery.

Uterine inertia that develops after a period of prolonged normal labor is referred to as secondary.

Weakness of pushing efforts arises In the second stage of labor due to poor abdominal Muscle tone or maternal exhaustion.

Uterine inertia develops in approximately 10% of delivering women. Primary uterine inertia may result from either a deficiency in the nerve impulses that initiate, maintain, and regulate labor, or the inability of the Uterus to adequately perceive or respond to these impulses with sufficient contractions. The Pathogenesis of uterine inertia is significantly influenced by decreased estrogen saturation, impaired prostaglandin synthesis, pathological alterations in protein, carbohydrate, lipid, and Mineral METABOLISM, as well as low activity of Enzymes in the pentose-phosphate carbohydrate cycle.

In uterine inertia, contractions are of low intensity (below 30 mmHg) and low frequency (fewer than 2 contractions per 10 minutes). Uterine tone is decreased (8 mmHg or less). Cervical effacement and dilation proceed at a reduced rate. The duration of labor increases, leading to maternal exhaustion and Fetal Hypoxia. Uterine inertia is also characterized by prolonged station of the fetal presenting part in the pelvic inlet plane and slow progression of the presenting part despite its adequate proportion to the dimensions of the true pelvis.

The Diagnosis of uterine inertia is established following dynamic observation of the laboring woman for 2–3 hours, or within 1–2 hours in the case of electronic fetal monitoring.

Management of Labor. In the event of maternal exhaustion and the absence of indications for immediate delivery (acute hypoxia, risk of obstetric fistulas), with cervical dilation up to 3–4 cm and intact amniotic membranes, a medicinal Sleep-rest regimen should be prescribed: promedol 2% – 1 ml, diphenhydramine 1% – 1 ml, atropine sulfate 0.1% – 1 ml; seduxen 0.5% – 2 ml or droperidol 0.25% – 1 ml may also be used. Obstetric anesthesia is administered by an anesthesiologist.

When cervical dilation exceeds 4–5 cm, the mother is in good spirits, and uterine inertia is present, Amniotomy is performed, followed 1–2 hours later by the augmentation of labor using uterotonic agents. In this context, contraindications to labor augmentation must be taken into account:

- fetopelvic disproportion (anatomically and clinically narrow pelvis);

- history of uterine scarring from previous surgeries (Cesarean Section, myomectomy, metroplasty, etc.);

- maternal exhaustion;

- abnormal fetal lie and presentation;

- intrauterine fetal compromise;

- Placenta Previa totalis;

- abruptio placentae (premature Separation of a normally or low-positioned placenta);

- vaginal stenosis, scars following third-degree perineal lacerations;

- dystocia, atresia, and cicatricial changes of the cervix;

- allergic reaction to uterotonics.

To stimulate labor activity, the following are used:

- intravenous drip infusion of oxytocin solution (5 IU dissolved in 500 ml of normal saline). Infusion is initiated at 6–8 drops per minute and gradually increased to 30–35 drops per minute, but not exceeding 40, to avoid uterine hyperstimulation;

- desaminooxytocin administered buccally (placing a tablet in the buccal pouch) starting at 25 IU with 30-minute intervals (up to 100 IU);

- intravenous administration of prostaglandin F_2а (2.5 mg) or E₂ (1 mg), prepared in 500 ml of normal saline and administered in the same manner as the oxytocin solution;

- other pharmacological and non-pharmacological agents.

It is impermissible to administer one labor stimulation protocol immediately after another. Spasmolytics are administered alongside uterotonics, but they should be used once active labor is established and cervical dilation reaches 3–4 cm. Repeated administration of spasmolytics is performed after 3–4 hours.

During labor in women with Primary Uterine Inertia (PUI), the condition of both the parturient woman and the fetus must be systematically monitored. For the Prevention of intrauterine fetal hypoxia, the following are administered intravenously (bolus or infusion): 40% 20 ml glucose solution, 1% 2 ml sygethin, 100 mg cocarboxylase, 5% 5 ml Vitamin C, 2.4% 10 ml aminophylline with glucose, alongside intermittent inhalation of 60% oxygen every 20–30 minutes.

Secondary uterine inertia. Secondary PUI can be promoted by factors similar to those involved in primary PUI, but it more frequently occurs in cases of:

- clinically narrow pelvis;

- fetal Hydrocephalus;

- malposition of the fetal HEAD;

- transverse and oblique fetal lie;

- cervical rigidity and scarring changes;

- vaginal stenosis;

- pelvic tumors;

- breech presentation;

- untimely rupture of membranes due to membrane toughness;

- endometritis;

- uncontrolled use of uterotonics, antispasmodics, or analgesics;

In secondary PUI, contractions that were previously of adequate strength become weaker and shorter, while intervals between them increase. Sometimes contractions cease altogether. The progression of the fetus through the birth canal halts. Labor becomes prolonged, which may lead to maternal exhaustion, endometritis, and fetal hypoxia.

In the event of secondary arrest of pushing efforts, intravenous oxytocin is administered at a rate of 20 to 40 drops per minute, and the Verbov binder is applied. Perineotomy or Episiotomy is performed according to indications. If medical augmentation of labor is ineffective and conditions permit, Obstetric Forceps are applied; in the absence of hypoxia and when conditions for forceps are lacking, a vacuum extractor may be used. Kristeller fundal pressure is highly traumatic for both mother and fetus and must not be used.