To analyze and summarize the clinical characteristics and ultrasonographic features of decidualized ovarian endometrioma (DOE) during pregnancy to provide a reference for its clinical diagnosis and treatment.

A retrospective analysis was conducted on the medical records of 11 patients clinically diagnosed with DOE during pregnancy at the General Hospital of the PLA from July 2021 to November 2024. The data included clinical information, ultrasound images, follow-up records, and surgical pathological results. The ultrasonographic characteristics and key points for clinical diagnosis and differentiation of DOE during pregnancy were summarized.

All patients exhibited ovarian cysts during pregnancy on ultrasound. The largest diameter of the endometriomas ranged from 3.1 to 7.3 cm, 90.9% (10/11) showed poor echogenicity of intracystic fluid, and the number of papillary projections ranged from 1-6 per cyst. Color Doppler flow imaging detected blood flow signals in 10 cases (flow scores: 2-3 in 72.7% [8/11]), and 72.7% (8/11) had a negative "sliding uterus sign". Three patients underwent surgical resection and had histologically confirmed benign DOE. Sign of decidualization disappeared in 8 cases during the follow-up period. Among these, one case had histologically confirmed benign DOE after surgery due to cyst rupture one year after pregnancy, The remaining 2 cases after abortion and 5 cases during pregnancy showed morphological changes in the cysts in the follow-up period, leading to a diagnosis of DOE based on clinical data.

DOE during pregnancy exhibits characteristic ultrasonographic features. Combining clinical characteristics and follow-up changes can improve diagnostic accuracy and avoid unnecessary surgical intervention. A dynamic follow-up observation strategy is recommended for suspected cases.