May Be Caused by

 Common

Gestational trophoblastic disease

Intervillous thrombosis

Maternal lake

Mature placenta

Normal subplacental complex

Septal cyst

Subchorionic lake

 Uncommon

Chorioangioma

Circumvallate placenta

Hematoma

Infarct

Metastasis

Perivillous or subchorionic fibrin deposition

Subchorionic thrombosis

Teratoma