Objective The number of women diagnosed with ovarian masses during pregnancy has increased in recent years and the management of these women can be controversial. We aim to describe ultrasound characteristics and clinical outcomes of patients with malignant ovarian masses diagnosed during pregnancy.

Methods Patients with a histological diagnosis of malignant ovarian mass detected during pregnancy who underwent pre-operative ultrasound by experienced ultrasound examiners between December 2000 and November 2017 were included in this retrospective observational study. Ultrasound characteristics of the masses were described using International Ovarian Tumor Analysis terminology. Patients with ovarian masses but without histopathological reports were excluded. Results are presented as absolute frequency (percentage) for nominal variables and as median (range) for continuous variables.

Results A total of 22 patients were included in the analysis. The median age was 32.5 (range 23–42) years and median gestational age at diagnosis was 13.5 (range 4–30) weeks. Eight (36.4%) patients had a serous/endocervical-type borderline tumor, seven (31.8%) patients had a primary epithelial ovarian carcinoma, five (22.8%) patients had a metastatic tumor to the ovary, and two (9%) patients had a mucinous borderline tumor. At ultrasound, mucinous borderline tumors were multilocular (1/2, 50%) or multilocular-solid (1/2, 50%) lesions. Serous/endocervical-type borderline tumors were unilocular-solid (3/8, 37.5%) or multilocular-solid (5/8, 62.5%) masses and all had papillary projections. Most invasive epithelial ovarian cancers were multilocular-solid masses (5/7, 71.4%). All metastatic tumors appeared as solid masses. No patients with borderline tumors had a cesarean section due to disease, whereas most patients with epithelial ovarian carcinomas (4/7, 57.2%) and with ovarian metastases (3/5, 60%) had a cesarean section due to disease. No neonatal complication was reported for patients with borderline tumors or epithelial ovarian carcinomas, whereas two of three newborns of patients with metastatic tumor died of the disease.

Conclusion At ultrasound, morphological features of malignant ovarian masses detected during pregnancy are similar to those described in non-pregnant patients. The likelihood of undergoing cesarean section increases with malignant disease in the ovary.