Retroplacental hematoma separates the placenta from the uterine wall centrally and is likely the result of bleeding from spiral arteries ( Fig 109-20). Sonographically it appears as a hypoechoic stripe between the placenta and underlying myometrium, but it may have variable echogenicity depending on the age of the bleeding. An acute hematoma may be isoechoic with the placenta, so it may appear as simply a thickened region of the placenta. It will become hypoechoic in 1 to 2 weeks. A retroplacental contraction may mimic a hematoma, and an old heterogeneous hematoma may look like a retroplacental fibroid. Retroplacental hematomas cause placental infarction and may result in fetal growth retardation, fetal death, and massive maternal hemorrhage. When a retroplacental hematoma is apparent sonographically, fetal mortality is directly related to the size of the hematoma.
FIG. 109-20. Placental abruption. This retroplacental hemorrhage is visualized in a patient during the third trimester of her pregnancy. Retroplacental abruptions carry a poorer prognosis than marginal abruptions. See Fig 109-15,.
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