Decidualized ovarian endometriomas are benign lesions that can closely mimic ovarian malignancy on ultrasound. Correctly identifying them is crucial to avoid unnecessary interventions and associated adverse fetal-maternal outcomes. A systematic review of the literature was performed to identify common sonographic patterns and key diagnostic features reported across gestation.

Thirteen studies comprising 35 cases were included. Ultrasound appearance evolved similarly: simple cysts with minimal vascularity in early pregnancy; rounded, vascularized papillary projections within cystic lesions during the second trimester; and solid-appearing, highly vascularized masses in the third trimester. Most cases were managed surgically. Expectant management was associated with postpartum regression and no reported complications. No malignant transformations were identified.

Recognizing these imaging patterns facilitates accurate diagnosis, reduces unnecessary surgical procedures during pregnancy, and supports safe expectant management. Awareness of the dynamic, gestational evolution of decidualized endometriomas is essential for physicians involved in prenatal care.