Influence of Intrauterine Fluid Detection, Number of Transfers and Age of the Recipient on Pregnancy Rate and Early Embryonic Loss in a Commercial Embryo Transfer Program.
Authors: Donato Gian Guido, Necchi Denis, Vandaele Hilde, Vita Micaela Elizabeth, Bertero Alessia, Vincenti Leila, Nervo Tiziana
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary Recipient mare selection critically influences embryo transfer success, yet the relative importance of candidate screening factors remains incompletely characterised in commercial settings. Guido and colleagues analysed 1,222 embryo transfer cycles to evaluate how recipient age, repeated transfers within a season, and intrauterine fluid presence affect pregnancy establishment and early loss rates. Mares receiving their first embryo of the year demonstrated substantially higher pregnancy rates at both 14 and 45 days (78.8% and 70.1%) compared to those at third transfer (65.6% and 54.1%), whilst intrauterine fluid detected post-ovulation significantly compromised 14-day pregnancy rates (60.5% versus 77.6%), indicating underlying uterine inflammation or impaired clearance. Interestingly, recipient age did not influence initial pregnancy establishment, though mares aged 10–13 years experienced markedly elevated early embryonic loss (15.6%) compared with younger mares aged 3–5 years (6.4%), and fluid presence during the follicular phase posed no reproductive detriment. These findings suggest that embryo quality remains paramount, but practitioners should scrutinise post-ovulatory intrauterine fluid as a significant red flag warranting investigation, reserve aged mares primarily for first transfers to maximise success, and recognise that seasonal transfer sequencing substantially impacts outcome predictions.
Read the full abstract on PubMed
Practical Takeaways
- •Prioritize recipient mares for their first embryo transfer cycle of the year, as they demonstrate substantially higher success rates and lower pregnancy loss
- •Post-ovulation intrauterine fluid is a red flag requiring investigation and possible treatment before transfer, as it reduces pregnancy success by approximately 17 percentage points
- •Consider age as a selection criterion: mares over 10 years old have significantly higher early pregnancy loss rates and should be used cautiously as recipients
Key Findings
- •Mares receiving their first embryo transfer of the year had significantly higher pregnancy rates at 14 and 45 days (78.8% and 70.1%) compared to those at their third transfer (65.6% and 54.1%)
- •Intrauterine fluid detected post-ovulation negatively affected pregnancy rate at day 14 (60.5% vs 77.6%) and should be considered abnormal, likely indicating uterine inflammation or delayed clearance
- •Recipient mare age 10-13 years showed higher early embryonic loss compared to mares aged 3-5 years (15.6% vs 6.4%)
- •Recipient mare age during follicular phase fluid detection and follicular phase fluid presence did not significantly affect pregnancy rates at day 14