Introduction/Background The number of women diagnosed with ovarian masses during pregnancy has increased in recent years and the management of these women is controversial.

Methodology To describe the diagnostic-accuracy of US in the differential diagnosis ovarian masses diagnosed during pregnancy. This is a retrospective single center study, approved by the local IRB. Clinical charts of pregnant women examined at our gynecologic oncology ultrasound center between 2000 and 2019 for a suspicious adnexal mass were retrieved. Ultrasound characteristics of the masses were described by using International Ovarian Tumor Analysis (IOTA) terminology.

Results 98 patients with an ovarian mass during pregnancy were found. Fifty-five women (56.1%) underwent close US monitoring each four weeks until delivery and one month after delivery. The remaining 43 cases (43.9%) underwent surgery for either high suspicious of malignancy, or high risk of side effects such as torsion, rupture or obstacle to pregnancy. Among them, 14 (32.5%) had a malignant tumor (10 primary ovarian and 4 metastatic tumor to the ovary), 17 (39.5%) had borderline ovarian tumor (4 mucinous and 13 serous histotype), 12 (28.0%) had a benign ovarian disease. At ultrasound, papillary projections were present in 16 of 31 malignant/borderline tumors (4 primary ovarian cancer and 12 borderline) and in 4 of 12 benign masses (p=0.281). The most frequent US feature was multilocular-solid mass (12/31, 38.7%) followed by unilocular-solid (9/31, 29.1%), solid (7/31, 22.5%) and multilocular (3/31, 9.7%). Accuracy rate of US with respect to final histological diagnosis was 76.7% considering BOT as primary ovarian tumors.

Conclusion Differential diagnosis of ovarian masses during pregnancy is still challenging and clinical management needs clear US rules.

Disclosure Nothing to disclose.