What are the causes of retroplacental (behind the placenta) hematoma?

Causes of Retroplacental Hematoma

The primary causes of retroplacental hematoma include placental abruption, hypertensive disorders of pregnancy (pre-eclampsia/HELLP syndrome), trauma, uterine anomalies, and coagulopathies. 1, 2

Definition and Pathophysiology

Retroplacental hematoma (RPH) refers to bleeding that occurs behind the placenta, between the placenta and the uterine wall. It is most commonly associated with placental abruption, which is characterized by premature separation of a normally implanted placenta before delivery of the fetus.

Major Causes

1. Hypertensive Disorders

• Pre-eclampsia: A significant risk factor for retroplacental hematoma 1
• HELLP syndrome: Hemolysis, elevated liver enzymes, and low platelets syndrome 1
• Severe hypertension: Can lead to vascular damage in the decidua basalis

2. Placenta Accreta Spectrum Disorders (PASD)

• Abnormal placental implantation due to defects in the decidua basalis 1
• Increased risk with:
  • Prior cesarean deliveries (risk increases 7-fold after one cesarean, 56-fold after three cesareans) 1
  • Placenta previa (present in 49% of PASD cases) 1
  • Prior uterine surgery or trauma 1

3. Decidual Vascular Abnormalities

• Abnormal physiologic changes in uteroplacental vessels 1
• Basal decidual defects leading to abnormal trophoblastic invasion 1
• Basal plate myometrial fibers (BPMF) associated with retroplacental blood clots 1

4. Obstetric and Maternal Factors

• Multiple parity: Paradoxically, multiparity appears to be protective [AOR: 0.38] 3
• Inadequate prenatal care: Fewer than 4 antenatal visits increases risk [AOR: 10.70] 3
• Advanced maternal age 1
• In vitro fertilization 1
• Smoking 1
• Uterine anomalies (congenital or acquired) 1

5. Trauma-Related Causes

• External trauma to the abdomen 1
• Uterine rupture 1
• Incision extensions during cesarean delivery 1

6. Coagulation Disorders

• Inherited coagulopathies 1
• Acute coagulopathy related to:
  • Amniotic fluid embolism 1
  • Severe pre-eclampsia 1
  • HELLP syndrome 1

Clinical Presentation and Diagnosis

Retroplacental hematoma may present with:

• Complete clinical syndrome: shock, uterine contracture, absence of fetal heart sounds 4
• Incomplete clinical syndrome (42.8% of cases): back pain and vaginal bleeding without shock, with preserved fetal heart sounds 4

Diagnostic imaging findings include:

• Ultrasound: Linear or biconcave, well-marginated mixed echogenic or anechoic region posterior to the placenta 5
• CT/MRI: May show hematoma within the uterine cavity 1

Complications

Retroplacental hematoma is associated with:

• Maternal hemorrhage requiring blood transfusion [AOR: 2.01] 3
• Low birth weight (<2500g) [AOR: 1.92] 3
• Fetal mortality in utero [AOR: 13.20] 3

Prevention and Management

Early recognition and management are critical to prevent significant maternal and fetal morbidity and mortality. The frequency of retroplacental hematoma is estimated at 5.20% of deliveries in some populations 3, highlighting the importance of:

• Regular, high-quality prenatal care
• Early diagnosis
• Prompt intervention, often via cesarean section 6

In established cases of retroplacental hematoma, emergency cesarean section is often indicated to reduce the risk of sudden and irreversible maternal and fetal complications 6.