ULTRASOUND OF PLACENTAL HEMATOMA

ULTRASOUND OF PLACENTAL ABRUPTION

Sonography in abruption often appears normal or may not truly reflect the gravity of the clinical signs, as no areas of bleeding are noted.

• Hypoechoic subchorionic area at the margin of the placenta that may be difficult to distinguish from the normal retroplacental venous plexus. Color doppler is useful as hematoma shows little or no blood flow whereas the retroplacental plexus is extremely vascular.

• Acute hemorrhage = hyperechoic to isoechoic in the first week (similar to the surrounding placental tissue and therefore may be difficult to diagnose antenatally). A negative ultrasound examination of the placenta does not exclude the diagnosis of acute retroplacental hematoma. This becomes hypoechoic from weeks 1-2 and is usually anechoic after week 2.

• Location.
• Subchorionic (most common).

• Retroplacental.

• Subamniotic hemorrhage.

• Pre placental.

Mortality is related to the degree of detachment (>50%) and the associated blood volume (>60 ml) and the location (retroplacental has the worst prognosis).

• Marginal hematomas occur most frequently in placentae that are partially implanted in the lower uterine segment or in placenta extrachorialis. In the first trimester these subchorionic hematomas probably result from early marginal placental abruption, with blood collecting below the chorionic membrane, instead of behind the placenta (second and third trimester).
• Retroplacental hematomas are found in 5% of all placentae and in 15% of women with pregnancy induced hypertension. Retroplacental bleeding with premature placental separation is thought to be due to rupture of a maternal uteroplacental artery. They are often accompanied by infarction of the overlying villous tissue and decidual necrosis.