Presumed monozygotic twins develop following transfer of an in vitro-produced equine embryo

An equine embryo produced by intracytoplasmic sperm injection (ICSI) was trans-cervically transferred to a recipient mare and pregnancy was confirmed via ultrasound examination on days 11, 12 and 15. On days 20 and 22, a single embryonic proper with a heartbeat was observed. On day 29, two embryos proper appeared during ultrasound examination, each possessing a heartbeat. Subsequent examinations on days 35 and 39 revealed continued viability and development of both embryos proper. On day 49, demise of both fetuses was present. Although no DNA analysis or post-partum examinations were performed, it is presumed that the fetuses were monozygotic twins based on membrane classification by ultrasound imaging as well as development occurring after the transfer of a single in vitro-produced embryo.