Blastocyst Transfer
Human embryos require a very specific environment for optimal growth that varies throughout differing stages of development. Standard culture media cannot meet these specific demands. Consequently human embryos, obtained through IVF treatment, have been routinely transferred to the uterine cavity on either Day 2 or Day 3 after egg collection when they are at the 4-Cell or 8-Cell stage respectively. With the introduction of sequential cultures for embryos at different stages of development, Embryologists have been able to culture embryos successfullly for longer in the laboratory up to the blastocyst stage (Day 5 after egg collection). This is the more usual practice now at the CRGH.
One of the causes of failure of IVF treatment is believed to be the growth arrest of embryos after transfer to the uterine cavity. The blastocyst embryo transfer does not differ from normal IVF treatment with regard to the preparation of the couple but it does help address this problem. By day 5 after egg collection the embryos have already survived a number of obstacles and consequently the chances of achieving a pregnancy are much higher compared to embryos transferred on Days 2 and 3. However, not all patients are suitable for blastocyst transfer and some will actually benefit from an early transfer rather than continued growth to the blastocyst stage.
Blastocyst transfer can be an option for patients with repeated IVF failure and for older patients with multiple, seemingly good, or poor quality embryos. In these cases the important consideration is that waiting for more days will enable us to select and replace those embryos which are of the best quality at this further stage of development. Blastocyst transfer may also help to reduce the risk of high order multiple pregnancy.
