B-Mode and Doppler Ultrasonographic Changes in the Corpus Luteum, Uterus, and Uterine Artery During Early Pregnancy in Cows

The aim of this study was to comparatively evaluate echotextural and hemodynamic changes in the corpus luteum (CL), uterus, and uterine artery, together with serum progesterone (P4) concentrations, using B-mode and Doppler ultrasonography between days 5 and 21 post-insemination in pregnant and non-pregnant cows. Twelve clinically healthy Brown Swiss cows were enrolled and allocated into a cyclic non-inseminated group (<i>n</i> = 6) and an inseminated group (<i>n</i> = 6). Ultrasonographic examinations and progesterone measurements were performed daily during the post-insemination period, and pregnancy was confirmed on day 30. Echotextural parameters (mean gray value and homogeneity) were obtained from the corpus luteum and uterus using B-mode ultrasonography. Doppler ultrasonography was used to assess corpus luteum vascular parameters and uterine artery blood flow, and serum progesterone concentrations were measured at each examination. Corpus luteum mean gray value showed a significant time effect (<i>p</i> < 0.001). For Corpus luteum area and perfusion area, both the time effect and the group × time interaction were significant (<i>p</i> < 0.001), and marked differences between pregnant and non-pregnant cows were observed on days 19, 20, and 21 (<i>p</i> < 0.05). Serum progesterone concentrations also differed significantly between groups on days 20 and 21. In conclusion, changes in corpus luteum area and perfusion area were associated with early pregnancy-related differences and may represent earlier functional ultrasonographic indicators compared with uterine artery Doppler parameters and progesterone concentrations alone. These findings may have practical implications for herd management by potentially enabling differentiation between pregnant and non-pregnant cows approximately 1-2 days earlier than serum progesterone measurements.