Clinical pregnancy outcomes after transfer of fresh and vitrified-warmed conventional IVF equine embryos

In vitro fertilization (IVF) in horses has emerged as a valuable assisted reproductive technology, yet the impact of embryo cryopreservation on pregnancy outcomes when utilizing this technique remains unclear. This study reports pregnancy outcomes following transfer of conventional equine IVF embryos, with both fresh and vitrified-warmed embryos. Conventional IVF (cIVF) was used to produce 40 embryos, which were transferred to recipient mares, pregnancy diagnosis was performed at 6 days post-transfer followed by embryonic heartbeat detection between day 25 and 30 of gestation. Observed pregnancy rates at 6 days post-transfer were 81% (17/21; 95% CI [58 to 95]) for fresh embryos and 79% (15/19; 95% CI [54 to 94]) for vitrified-warmed embryos. Embryonic heartbeat was detected in 94% (16/17; 95% CI [71 to 100]) and 100% (15/15; 95% CI [78 to 100]) of pregnancies, respectively. Given the retrospective design and limited sample size, findings are presented as descriptive outcomes and do not support inference regarding comparative efficacy. These observations contribute clinical outcome data for cIVF embryo transfer and support the need for larger, prospective studies with controlled recipient management and embryo characterization.