The recipient’s Day after ovulation and the number of corpora lutea influence the likelihood of pregnancy in mares following transfer of ICSI frozen embryos.

The researchers examined the correlations between a mare’s day after ovulation and corpora lutea count on the likelihood of successful pregnancy following transfer of intracytoplasmic sperm injection (ICSI) frozen embryos. They found that the timing of the embryo transfer and the count of corpora lutea significantly affected the rate of sustained pregnancy.

Objective of the Research

• The researchers aimed to determine whether the day after the mare’s ovulation and the number of Corpora Lutea (CL) at the time of Embryo Transfer (ET) have an impact on the success of In-Vitro Produced (IVP) horse embryo’s pregnancy rates.

Methodology and Scope of the Study

• A retrospect study was carried out involving 650 heterologous frozen ICSI horse embryo transfer cycles.
• The study assessed the rates of pregnancy as well as ongoing pregnancy.

Key Findings

• The ongoing pregnancy rates were significantly lower in mares where embryo transfer took place 5 and 6 days after ovulation, with rates of 47.4% and 37.5% respectively.
• Recipients of embryo transfer on the fourth day after ovulation had a higher rate of ongoing pregnancy at 67.3%.
• Mares on day five (considering the day of ovulation as Day 0) with two CL had lower ongoing pregnancy rates (36.1%) compared to those with one CL(51.9%).
• Interestingly, the presence of two CL was associated with higher ongoing pregnancy rates (75.8%) in mares whose embryo transfer happened on days 3 and 4 after ovulation, when compared to mares with just one CL at the time of embryo transfer (62.7%).

Conclusions

• The study concludes that both the number of days after the mare’s ovulation and the number of corpora lutea at the time of embryo transfer played a significant role in determining the ongoing clinical pregnancy rate.
• This underlines the significance of accurately establishing when progesterone levels rise beyond a certain threshold after the day of ovulation to deduce the most effective window for transferring an IVF/IVP embryo.