Embryo Transfer - Anatomy & Physiology

Introduction

Multiple ovulation and embryo transfer has been commercially available since the 1970s, but not widely used because it requires a highly skilled team.

Synchronization of Recipients with the Donor

• GOAL: To synchronize the donor and recipient to be in the same stage of the oestrous cycle.
• REASON: To prepare the uterus of the recipient to support preattachment embryogenesis.
• HOW: Treat recipient with a hormonal regime that induces oestrus to occur at the same time as the donor.

Superovulation of the Donor

• GOAL: To hyperstimulate ovaries with gonadotrophins.
• REASON: To provide higher than normal numbers of follicles that reach dominance and ovulate.
• HOW: Inject donor with gonadotrophins to hyperstimulate follicular development. Generally FSH or one of its analogs is used.

Inseminating the Donor

• GOAL: Inseminate donor with semen from genetically superior bulls. To generate the best fertilisation rates and genetic combinations possible.
• REASON: Enhance rate of genetic progress.
• HOW: Use highly fertile semen and well-trained, experienced inseminators.

Recovery and Identification of Viable Embryos

• GOAL: To nonsurgically collect (flush) embryos from the donor to transfer.
• REASON: To recover viable embryos.
• HOW:
  • Before the procedure is started, a local anaesthetic is injected to cause relaxation of the rectum.
  • At day 6-8 a specialized catheter has a small balloon that can be inflated to prevent retrogade flow of the flushing medium.
  • A flushing medium is then introduced into the uterus, lavaged and returned through the catheter to a collection vessel.

Transfer of Viable Embryos into Synchronised Recipients

• GOAL: To deposit a potentially viable embryo into the uterine horn of each recipient.
• REASON: To achieve pregnancy in each recipient.
• HOW:
  • Both donor and recipient have a corpus luteum at similar stages of leutinization.
  • Uterine environment in the donor and recipient are quite similar.
  • A single embryo is placed into the uterine horn using a transfer pipette.