Obstetrics and Gynecology - A.M. Gromova 2000

Obstetric Hemorrhage
Premature Abruption of a Normally Positioned Placenta

Premature detachment of a normally situated Placenta (placental abruption) refers to the Separation of the placenta before the delivery of the fetus, occurring during Pregnancy or in the First and Second stages of labor. This pathology occurs in 0.5-1.5% of all deliveries.

Etiology AND Pathogenesis

Placental abruption most commonly develops in the presence of conditions associated with vascular disorders, such as late pregnancy toxemia (Preeclampsia), especially when combined with extragenital pathologies: Hypertension, Pyelonephritis, Diabetes Mellitus, Heart and Liver diseases, and recent acute viral infections.

During labor, placental abruption can be triggered by an abnormally short or relative length of the umbilical cord, uncoordinated uterine activity, rapid rupture of membranes in polyhydramnios, late Amniotomy, localization of the placenta over a fibroid node, chronic Fetoplacental insufficiency, or abdominal trauma.

The primary pathogenetic factor in The Development of placental abruption is The formation of basal hematomas within the decidua, resulting from increased vascular fragility in both the decidua and the adjacent myometrium. Placental abruption is preceded by chronic impairment of uteroplacental Blood flow: vasospasm of arterioles and capillaries in the basal layer of the decidua, increased blood viscosity, and the release of blood thromboplastin. Impaired microcirculation in the placenta leads to decreased elasticity of the vascular walls and increased permeability, promoting the rupture of arterioles and capillaries. This forms microhematomas that gradually coalesce, disrupting the basal plate of the decidual tissue, involving the intervillous spaces, and forming a retroplacental hematoma. As blood infiltrates the uterine wall, the neuromuscular apparatus is damaged, and metabolic processes and MOTOR FUNCTION OF the Uterus are severely disrupted. Initially, the uterus may become hypertonic, subsequently becoming flaccid, and leading to hypotonus or atony. Due to uneven blood infiltration, the uterus acquires a mottled purple color and fails to respond to mechanical or pharmacological stimulation. This condition is known as a "Couvelaire uterus" or "uteroplacental apoplexy".

The first two cases were described in 1912 by the French physician A. Couvelaire, after whom this pathology is named. According to modern understanding, placental abruption is preceded by a chronic form of disseminated intravascular coagulation (DIC) within the uteroplacental Circulation, which develops in severe forms of preeclampsia. Placental abruption facilitates the transition from the chronic form of DIC syndrome to the acute form, accompanied by generalized bleeding and hemorrhagic Shock.

Clinical presentation

Placental abruption can be complete (detachment of the entire placenta) or partial, progressive or non-progressive, mild, moderate, or severe, and spontaneous or induced (resulting from mechanical trauma). The clinical course of placental abruption depends on the extent of detachment and the severity of associated pathology. Partial detachment over a small area during labor is sometimes impossible to diagnose clinically; it is typically recognized only after delivery by the presence of an old blood clot on the maternal surface of the placenta.

The main symptoms of placental abruption are bleeding and pain. The bleeding may be internal, external, or combined, depending on the site of placental detachment. If the hematoma is centrally located, external bleeding may be absent initially or appear later. When detachment begins at the periphery, even a small hematoma can rapidly dissect the membranes, resulting in external Hemorrhage. Internal hemorrhage poses the greatest threat. The patient's general condition deteriorates, blood pressure drops, and she develops tachycardia, weakness, and pallor of the Skin and mucous membranes.

The second primary symptom is pain. Initially, pain is localized to the site of placental separation and is more pronounced when a retroplacental hematoma forms, prompting Complaints of severe, bursting abdominal pain. Gradually, the pain spreads to other Regions of the uterus. Objective Examination reveals Asymmetry, tension, hypertonus, and tenderness of the uterus upon Palpation, while fetal parts are difficult to outline. Vaginal examination reveals a persistently tense amniotic sac and blood-tinged Amniotic Fluid. The placenta is delivered immediately following the baby. In the postpartum period, hemorrhages frequently occur secondary to uterine hypotonia.

Detachment of up to 1/3 of the placental surface leads to fetal Hypoxia, whereas detachment exceeding 1/3 results in fetal demise, particularly when morphological or functional signs of placental insufficiency are already present.

Given that bleeding is also a major symptom of Placenta Previa, Differential Diagnosis between these two conditions is essential.

Ultrasonography plays a crucial role in diagnosing placental abruption and placenta previa. The diagnosis of placental abruption is definitively confirmed by pathomorphological examination. External inspection of the maternal surface of the placenta after delivery reveals a depression (facet) filled with a blood clot. If the detachment occurred during labor, this depression may be absent, showing instead thin, dense blood clots at the site of separation. A more precise diagnosis is established via microscopic examination (widespread microinfarctions, villous sclerosis, fibrin thrombi, thinning, and absence of decidual tissue).

The choice of delivery method depends on the volume of blood loss and the clinical conditions permitting a specific surgical intervention. In cases of placental abruption During the first stage of labor, a Cesarean Section is performed.

During the Second Stage of labor, operative delivery is indicated—such as the application of obstetrical forceps or Breech Extraction for a living fetus, or a destructive operation if the fetus is dead. Concurrently, aggressive measures are taken to manage blood loss and shock.

When There is a prolonged interval between placental detachment and delivery, damage to the uterine neuromuscular apparatus occurs, leading to uteroplacental apoplexy, which subsequently results in uterine atony and hypotonia. Furthermore, coagulation defects promote the rapid development of hemorrhage, DIC syndrome, and hemorrhagic shock. If intraoperative inspection reveals blood infiltration of the uterine wall ("Couvelaire uterus" or "shock uterus"), Hysterectomy (total hysterectomy without adnexa) is indicated.

Prevention of placental abruption involves the timely detection and management of pregnant women with late preeclampsia and somatic diseases. Gentle Management of Labor is equally important—avoiding aggressive fundal pressure and ensuring gradual release of amniotic fluid in cases of polyhydramnios.