Assessment of endometrial and subendometrial three-dimensional power Doppler angiography evaluated by the VOCAL method in frozen-thawed embryo transfer cycles on hormone replacement therapy

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BACKGROUND: The effectiveness of in vitro fertilization cycles / frozen-thawed embryo transfer cycles depends on a number of factors, the endometrial one being of great importance. Adequate endometrial and subendometrial blood supply is considered necessary for successful implantation. Currently, the possibilities of non-invasive assessment of the implantation properties of the endometrium are limited to the use of ultrasound. AIM: The aim of this study was to assess the performance of endometrial and subendometrial three-dimensional power Doppler angiography combined with the Virtual Organ Computer-aided Analysis (VOCAL) method in frozen-thawed embryo transfer cycles on hormone replacement therapy and compare the obtained data among the women examined. MATERIALS AND METHODS: This prospective study included 20 women. Doppler measurements were carried out three times — on the day of progesterone initiation, the day before embryo transfer and on the day of embryo transfer. The VOCAL software assessed the endometrial and subendometrial volume and blood flow indices such as vascularization index, flow index, and vascularization flow index. Patients were divided into two study groups depending on the onset of clinical pregnancy. RESULTS: On the day of progesterone initiation among patients who got pregnant, we observed higher vascularization (3.52 ± 1.99 vs. 1.05 ± 1.36; p = 0.03) and vascularization flow (1.54 ± 0.98 vs. 0.63 ± 0.55; p = 0.03) indices compared to women with a negative result. Moreover, endometrial vascularization index on the day of progesterone initiation was positively correlated with the estrogen dose among both pregnant (r = 0.61; p = 0.04) and non-pregnant (r = 0.9; p = 0.0008) women. No differences in subendometrial blood flow indices depending on the onset of pregnancy were obtained, just as endometrial blood flow indices the day before embryo transfer and on the day of embryo transfer were comparable between women in the both study groups. CONCLUSIONS: Three-dimensional power Doppler angiography evaluated by the Virtual Organ Computer-aided Analysis (VOCAL) method is a promising tool for non-invasive assessment of endometrial receptivity in frozen-thawed embryo transfer programs. However, further studies are required on a larger patient sample to form conclusions that are more accurate.