The Role of Endometrial Volume and Endometrial and Subendometrial Vascularization Parameters in a Frozen Embryo Transfer Cycle.

The role of three-dimensional power Doppler ultrasonography of the endometrium in assisted reproduction is still far from clear. In this retrospective cohort study, transvaginal three-dimensional power Doppler examinations were performed 30 min before frozen-thawed embryo transfer. After pregnancy tests, two cohorts were established: P (pregnant, n = 31) and NP (nonpregnant, n = 31). The study only included nullipara with no uterine abnormalities who were undergoing infertility treatment at the Department of Gynecology, Obstetrics and Gynecological Endocrinology, Kepler University Hospital, Linz, Austria. The main outcome measures were the vascularization flow index (VFI), flow index (FI), and vascularization index (VI) in the endometrium/subendometrium, assessed using Virtual Organ Computer-aided AnaLysis (VOCAL™), and the endometrial volume. A total of 62 patients were enrolled in the study, forming two cohorts (pregnant, P; nonpregnant, NP). There were no significant differences between the two cohorts with regard to demographic data, numbers of embryos transferred, or embryo grading, but there was a significant difference in endometrial volume (cohort P, 3.17 ± 0.84 mL; cohort NP, 2.36 ± 0.9 mL; P = 0.001) and the pregnancy rate rises with larger volume. No differences were observed in the vascularization parameters FI, VFI, and VI in the endometrium and subendometrium. In the cohort of pregnant patients, there were 26 (41.9%) live births, with 21 term deliveries (80.8%). The endometrial volume was larger in the cohort of pregnant patients. Measurements were performed 30 min before embryo transfer, and no differences were observed in vascularization parameters in the subendometrium and endometrium.