Abnormal cleavage patterns tied to early loss in equine IVP embryos

CURRENT BRIEF VERSION: Abnormal cleavage patterns seen on time-lapse imaging in equine in vitro-produced embryos were linked to markedly worse early pregnancy outcomes in a new Equine Veterinary Journal study from researchers at UC Davis and collaborators. In a retrospective analysis of 70 transferred embryos and 114 arrested embryos, embryos with abnormal first-division cleavage patterns had a total early pregnancy loss rate of 53.3%, versus 22.6% for embryos with normal cleavage. Earlier vitrification, a proxy for faster blastocyst formation, was also associated with better odds of pregnancy at day 14 and lower loss through day 25. The paper was published online ahead of print on July 31, 2025. (pubmed.ncbi.nlm.nih.gov)

Why it matters: For equine reproduction teams, the findings add support for using morphokinetic assessment during the first mitotic division as a practical embryo-selection tool, especially in ICSI/IVP programs where early loss remains a persistent problem and standardized grading criteria are still evolving. The work also fits with earlier equine IVP research showing that faster embryo development is tied to better downstream outcomes, while other retrospective data suggest pregnancy rates are also shaped by post-thaw embryo grade, donor mare age, transfer timing late in the breeding season, and in some mares, the stallion used for ICSI. (pubmed.ncbi.nlm.nih.gov)

What to watch: Whether clinics translate time-lapse cleavage assessment into routine transfer protocols, and whether prospective studies confirm that selecting against abnormal cleavage can improve pregnancy retention in commercial equine IVP programs. It will also be worth watching how these lab-based markers are combined with known clinical variables such as donor mare age, embryo yield per session, and mare-stallion pairing in underperforming donors. (vetart.vetmed.ucdavis.edu)