A blastocyst is the name given to an embryo that is 5-6 days old. A blastocyst embryo transfer does not differ from a normal embryo transfer during IVF treatment nor in relation to the preparation of the couple undergoing treatment, but simply refers to the age of the embryo in terms of its development at the stage of transfer.
Not all patients are suitable for a blastocyst transfer. Some patients may benefit from an early transfer rather than continued growth to a blastocyst stage especially if they have a very small number of good quality embryos. However, a blastocyst transfer can be an option for patients with repeated IVF failure or for older patients who have multiple, seemingly good or poor quality embryos.
A blastocyst transfer may also help to reduce the risk of high order of multiple pregnancies in younger patients for whom one single blastocyst can be transferred. Blastocyst stage embryos do have a higher chance of achieving a pregnancy compared to day 3 embryos. This can be attributed to the fact that the embryos have undergone a further selection process of eliminating embryos that have failed to develop into blastocysts. Typically around 60% of day 3 embryos will develop to the blastocyst stage.
The embryos are cultured for an extended period of time in our laboratory and are transferred back into the uterus either five or six days after egg collection. This helps to us to improve the selection of your best quality embryo(s) with the greatest potential for development after a transfer.
Our embryologist will grade the two cell lines in the blastocysts; namely the Inner cell mass (ICM) and the Trophectoderm (TE).Any surplus good quality blastocysts can be frozen for future use.
One of the risks associated with a blastocyst embryo transfer is that there is a higher rate of cancellation of the cycle (i.e. no embryos being available for transfer due to no blastocyst formation). A blastocyst transfer has also been associated with a higher rate of monozygotic (identical) twins.
In addition, recent work on animals, namely cattle and sheep, showed that prolonged embryo culture followed by a blastocyst embryo transfer could, in some cases, lead to neonatal problems, notably increased birth weight and congenital abnormalities. There is no evidence, so far, of similar findings following transfer of human embryos at the blastocyst stage.