Classification of Placental Abruption
Depending on the area of detachment, two types are distinguished:
- Partial — only a fragment of the placenta separates from the uterine wall.
- Complete — the entire placenta separates, which is accompanied by both internal and external bleeding.
Partial abruption is further classified by location:
- Marginal: the edge of the placenta separates. As a rule, blood finds an exit, and external bleeding is observed.
- Central: the central part separates. Blood accumulates between the placenta and the uterine wall, forming a retroplacental hematoma (internal bleeding).
Depending on the clinical course, the process can be progressive or non-progressive. In a non-progressive form with a small area, the hematoma condenses and partially resolves, pregnancy continues, and the detachment site is identified retrospectively upon visual inspection of the placenta after delivery.
Etiology and pathogenesis
The exact cause of placental abruption is not fully established. The pathology is considered a consequence of systemic (sometimes occult) diseases in the pregnant woman and coagulopathies. Three main groups of factors are distinguished:
- Vascular (vasculopathy): endothelial damage in arterial hypertension, preeclampsia, or glomerulonephritis impairs the permeability and integrity of the vascular wall.
- Hemostatic (thrombophilia): congenital and acquired defects (antiphospholipid syndrome, factor V Leiden mutation, antithrombin III and protein C deficiency) cause defective trophoblast invasion. During abruption, tissues with high thromboplastic activity enter the maternal circulation, triggering acute disseminated intravascular coagulation (DIC).
- Mechanical: occurs with a sharp decrease in the volume of an overdistended uterus or frequent, intense contractions. The placenta lacks the ability to contract and detaches from the myometrium.
Pathogenesis begins with the primary rupture of vessels in the decidua basalis. The resulting hematoma destroys all layers of the decidua and mechanically separates the placenta from the uterine wall.
Predisposing factors
The risk of placental abruption increases under the influence of various triggers:
- During pregnancy: extragenital vascular and endocrine disorders (diabetes mellitus, glomerulonephritis), autoimmune conditions (systemic lupus erythematosus, antiphospholipid syndrome), allergic reactions to blood transfusions or dextrans, as well as preeclampsia.
- During labor: rapid escape of amniotic fluid in polyhydramnios, birth of the first fetus in a multifetal pregnancy, short umbilical cord, delayed rupture of membranes, and uterine hyperstimulation with oxytocin.
- Traumatic (violent) factors: falls and trauma, amniocentesis, external cephalic version.
Obstetric Tactics and Operative Delivery
Bleeding after amniotomy (rupture of membranes) is an absolute indication for Cesarean section (CS).
Ivanov–Gauss skin-traction forceps may be used in rare cases, but only under strict conditions: incomplete placenta previa, absence of bleeding during preterm labor, dead or non-viable fetus (lethal malformations), status post-amniotomy, and a mobile fetal head above the pelvic inlet. If forceps application is ineffective, CS is performed immediately.
In case of massive hemorrhage, combined general anesthesia is the method of choice for pain relief. Elective CS with stable hemodynamics and no hypocoagulation allows the use of regional anesthesia.
Surgical Hemostasis in Massive Hemorrhage
The surgery is performed by an experienced surgeon as part of an expanded team (surgeons, anesthesiologist-resuscitologist, neonatologist trained in neonatal resuscitation, transfusiologist). An autologous blood recovery device (intraoperative cell salvage) must be ready in the operating room.
In massive blood loss, hemorrhagic shock, and acute fetal hypoxia, lower midline laparotomy is indicated. The uterine incision should preferably be made outside the placental location. If transplacental access is used, the surgeon makes a quick incision in the lower segment, cuts through the placenta, delivers the fetus without detaching the placenta, and then manually removes it.
The following are used to stop bleeding:
- Intravenous administration of uterotonics (oxytocin, carbetocin) immediately after placental delivery.
- Suturing the inner surface of the uterus in the placental bed area.
- Uterine artery embolization (catheterization via the femoral and internal iliac arteries, administration of 510–700 micron embolic agents under angiographic control).
- Surgical ligation of the uterine or internal iliac arteries.
If all the above measures are ineffective and bleeding persists, hysterectomy is indicated.
Briefly: answers to topical questions
What specific CTG and ultrasound changes are characteristic of premature placental abruption?
Specific instrumental changes in premature placental abruption include visualization of a retroplacental hematoma and registration of an abnormal cardiotocogram.
- Ultrasound examination — detection of hypoechoic foci or zones between the placenta and the uterine wall, which helps determine the location, area of abruption, and size of the hematoma.
- Cardiotocography — detection of fetal heart rate abnormalities; an abnormal trace is a predictor of an adverse outcome.
What is Couvelaire uterus and what is the mechanism of its formation in placental abruption?
Couvelaire uterus (uteroplacental apoplexy) is a severe pathological condition in which the uterine wall is totally infiltrated with blood. The mechanism of its formation is due to the accumulation of blood between the uterine wall and the placenta. The resulting retroplacental hematoma creates high pressure, causing blood to penetrate into the myometrium and reach the serosa. The serous cover of the uterus acquires a bluish color with multiple petechiae. With a Couvelaire uterus, the contractility of the myometrium is often impaired, which can contribute to the progression of DIC syndrome and massive hemorrhage.
What are the clinical severity grades of placental abruption distinguished in obstetrics?
In obstetrics, mild, moderate, and severe clinical grades of premature placental abruption are distinguished.
- Mild degree — a non-progressive form with a small retroplacental hematoma, without impairment of maternal and fetal condition and without pronounced external or internal bleeding.
- Moderate degree — detachment of 1/3–1/4 of the placental area. In marginal abruption, significant bleeding with clots is noted; in central abruption, abdominal pain, uterine hypertonus, and acute fetal hypoxia occur.
- Severe degree — detachment of more than 1/2 of the placental area. Manifests as sudden abdominal pain, symptoms of internal hemorrhage, and rapid development of hemorrhagic shock; the fetal condition is characterized by acute hypoxia or intrauterine fetal demise.
Three groups of causes of placental abruption: Vascular (vasculopathies), Hemostatic (thrombophilias), and Mechanical (overdistension, trauma).
Class and exam questions
What makes central placental abruption particularly dangerous?
In this condition, blood does not escape outwardly, but accumulates between the placenta and the uterus, forming a retroplacental hematoma. Due to high pressure, placental tissue cells enter the maternal circulation, which can trigger acute DIC syndrome.
Does placental abruption always require emergency delivery?
No. There is a non-progressive form of partial abruption. If the area of detachment is small, the hematoma can condense and partially resolve without disrupting fetal development, and pregnancy will safely continue.
What errors in labor management can provoke placental abruption?
Iatrogenic and mechanical risk factors in labor include uterine hyperstimulation with oxytocin and a sharp change in uterine volume (e.g., during rapid escape of amniotic fluid in polyhydramnios).
What else to study on this topic
- Prevention of impaired uterine contractility in the postpartum period
- Transplacental access technique in cesarean section
- Endovascular surgery methods in obstetrics: uterine artery embolization
- Early postpartum complications: uterine hypotonia and placenta accreta
- Indications and conditions for the application of Ivanov–Gauss scalp traction forceps
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