Sonolucent areas in the placenta: sonographic and pathologic correlation.

With the advent of gray scale ultrasonography, the internal structure of the placenta can be defined in great detail. Subchorionic sonolucent areas visualized on antepartum sonograms correlate with areas of subchorionic fibrin deposition, hematoma, and cystic degeneration in the term placenta. These lesions are apparently of no clinical significance. However, diffuse intraplacental sonolucent cystic lesions are abnormal and are seen in both hydatidiform mole and hydropic swelling of the placenta.