This study examines the use of ultrasonography in predicting successful pregnancy outcomes in horses during embryo transfer programs. Researchers discovered that measuring luteal blood perfusion, a physical characteristic indicating how much blood is reaching the corpus luteum, can effectively identify recipients with the highest probability of maintaining a pregnancy.

Study Aim and Methodology

• The primary objective of this study was to determine the impact of certain characteristics of the corpus luteum (CL, a temporary endocrine structure involved in reproduction) and uterus on pregnancy outcomes.
• These properties were evaluated via ultrasonography in recipient mares (a group of 110 horses) at the time of embryo transfer (ET), which ranged between days 3-9 after spontaneous ovulation.
• The reproductive system of each mare was assessed for a multitude of parameters. Some of these included uterine tone, CL echogenicity (a measure of how sound waves are absorbed or reflected), CL type, luteal area, uterine echogenicity, uterine edema (swelling), luteal blood perfusion, and uterine blood perfusion.
• In addition, blood samples were collected for the measurement of progesterone levels (P4, a hormone crucial for the maintenance of pregnancy).

Results and Analysis

• The results showed that luteal blood perfusion, which indicates the amount of blood delivered to the CL, was significantly higher in pregnant mares compared to those not pregnant.
• The probability of a successful embryo transfer was higher in mares with high luteal blood perfusion and high levels of P4.
• Notably, the most significant predictor of successful pregnancy was identified as luteal blood perfusion, more so than luteal area and plasma P4 concentration.
• Only luteal blood perfusion showed an effect on the probability of a successful embryo transfer, indicating a relationship both linear (a direct proportion between two quantities) and cubic (a relationship involving the cube of a quantity), affecting the outcome of the embryo transfer.

Conclusion

• The study concluded that luteal blood perfusion, as gauged by color-Doppler ultrasonography, can be used to real-time select the best recipient mares with the highest chance of maintaining a successful pregnancy in equine ET programs.
• Therefore, this finding could improve the efficiency of these programs by enabling the identification of potential successful recipients before the process begins.