Relationship between colour flow Doppler sonographic assessment of corpus luteum activity and progesterone concentrations in mares after embryo transfer.

This research examines the relationship between corpus luteum activity and progesterone concentrations in mares after embryo transfer, using Colour-flow Doppler sonography as the investigative method. The research concluded that although corpus luteum area and blood flow are related with progesterone levels during the time of and after transfer, the evaluation of the corpus luteum through sonography does not improve the selection of recipients or pregnancy outcome predictions.

Research Background and Purpose

• The study was set to investigate the connections between the area and vascularization of corpus luteum (an endocrine structure involved in reproduction), and concentrations of progesterone (a hormone crucial for pregnancy) in the early pregnancy stage in mares.
• The research also aimed to determine if the blood flow in the corpus luteum could be a useful parameter for selecting a suitably timed and prepared recipient mare for an embryo transfer.

Methodology

• Equine embryos were collected 8 days after ovulation and subsequently transferred to suitable recipient mares whose ovulation was synchronized to varying degrees with the donor. The synchronization varied from one day prior to four days after the donor’s ovulation.
• The maximum cross-section and blood vessel areas of the corpus luteum were assessed sonographically just before the embryo transfer, and the mares’ blood was also collected to measure plasma progesterone levels. These measurements were repeated at several points after the embryo transfer.
• The pixels within the corpus luteum area were then quantified using ImageJ software.

Findings

• Correlation was found between the blood flow in the corpus luteum and plasma progesterone levels at the time of transfer and 4 days after the procedure for all mares, and also on days 11 and 25 for those mares that became pregnant.
• Correlation was also observed between the corpus luteum area and plasma progesterone levels up to day 11 after the embryo transfer.
• The area of blood flow (as represented by colour pixel area) within the corpus luteum, as well as the area of the corpus luteum itself, began to decrease several days after the embryo transfer.
• Despite these correlations, the area or blood flow of the corpus luteum or progesterone levels were not found to be predictive of pregnancy.

Conclusion

• The research concludes that while there are correlations between the area and blood flow of the corpus luteum and the progesterone levels, these factors do not provide significant predictive value for pregnancy or improve the selection of recipient mares for embryo transfer.