Prediction of ovarian tumor type in pregnant women is of great clinical significance, however, it is vastly difficult. In the last 5–10 years gynecologists were suggested to use RMI (Risk of Malignancy Index) in non-pregnant women, however the value of the test for obstetric practice has yet to be established. The study was aimed to determine RMI-IV and RMI-V during preoperative non-invasive prediction of ovarian tumor type in pregnant women. Retrospective and prospective clinical and laboratory data of 114 pregnant women aged 20–38 were collected. Among them 15 patients had malignant ovarian tumors (MOTs), 28 had borderline ovarian tumors (BOTs), and 71 had benign ovarian tumors. Color Doppler and pulsed wave Doppler ultrasound was performed. The levels of СА-125 were defined by enzyme immunoassay. Models IV, V were used to assess the risk of ovarian cancer. A moderate non-significant increase in blood levels of СА-125 compared to patients with benign ovarian tumors and BOTs was found in pregnant women with MOTs. Patients with BOTs and MOTs showed higher RMI-IV and RMI-V values compared to the group of pregnant women with benign ovarian tumors. Extreme values are required to guarantee the differences in the diagnosis of tumors (RMI-IV > 3500 indicate the presence of MOTs, the values below 100 indicate no malignancy). Similar RMI-V values are 1500 and 60. However, in most cases, availability of RMI-IV and RMI-V is insufficient for decision making, and a comprehensive approach has to be used. Thus, it is difficult to define ovarian mass type in pregnant women using RMI only. Comprehensive clinical assessment with the use of imaging methods is required for preoperative prediction of ovarian mass type in pregnant women, along with the use of prognostic models taking into account the majority of descriptive “morphological” tumor characteristics.

Currently, surgical treatment aimed to exclude the malignant ovarian tumors is performed in almost 90% of patients with decidualized endometrial cysts (DEC). However, unnecessary surgical interventions increase the risk to maternal and fetal health. The study was aimed to perform a differential diagnosis of DEC in pregnant women in order to define the rational treatment. A total of 82 female patients were included in the study: 63 had endometrial cysts (EC), 16 had DEC, 3 had rare forms of endometriosis, and 10 had ovarian serous papillary borderline tumors. When performing the diagnostic ultrasound, our proposed model was used. The ultrasound imaging data obtained were juxtaposed with the concentration of the protein tumor markers (СА-125), the risk of malignancy index (RMI) was calculated, and the morphological assessment of the masses was performed. The ultrasound imaging parameters, being the most valuable for differential diagnosis of EC, DEC, and serous borderline tumors, were as follows: the altered mass wall thickness, the existence and shape of papillary masses, avascular echogenic inclusions with blurry contour, blood circulation and arrangement of blood vessels, ascites. The frequency analysis revealed the differences between groups based on the ultrasound imaging data (in 60–100% of observations). Histological examination revealed the differences between groups in 100% of observations. Our findings have made it impossible to prolong pregnancy in patients with DEC without performing surgery. The results of treatment provided to patients with DEC during pregnancy were worse compared to those in patients with no prominent decidualization in ovarian EC. Today, the diagnosis of DEC and the treatment of patients during pregnancy remain unsophisticated. Further clinical observation and the search for more reliable methods of the diagnosis and rational treatment of pregnant women with DEC are required.