More on Blastocyst Transfer
At this stage the embryo consists of 60-120 cells, forming two distinct groups. The outer layer of the blastocyst consists of cells collectively called the trophoblast that will give rise to the placenta and the inner cell mass (embryoblast) which subsequently forms the embryo. The next stage is blastocyst hatching out of its shell (zona pellucida).
The rhythmic expansions and contractions result in the embryo that grows in volume, bulging out of and emerging from the thinning zona pellucida. This is also supported by enzymes that dissolve the zona. The zona pellucida surrounding the blastocyst breaches and the blastocyst is hatched until it is completely released from its surrounding shell.
Blastocyst transfer (5th or 6th day after egg retrieval) is exactly the same as embryo transfer on days 2 or 3.
Advantages of blastocyst transfer include:
√ Allowing “self-embryo selection” thus permitting transfer of high quality embryos.
√ High pregnancy rates in certain cases.
√ Better embryonic – endometrial synchronization.
√ Single embryo transfer (compared to 2 or 3 embryos usually transferred) that reduces the incidence of multiple pregnancies.
√ Monitoring cases of Ovarian Hyperstimulation Syndrome (OHSS) and proceed to embryo transfer only if the condition improves.
When is blastocyst transfer recommended?
Blastocyst culture is not an option for all couples. Development of many, good quality embryos is a prerequisite. Blastocyst transfer is suitable for:
√ women with polycystic ovaries, where high numbers of oocytes are retrieved.
√ women in risk of developing OHSS.
√ cases of severe oligoasthenoteratozoospermia or testicular biopsy.
√ cases with a history of previous failed cycles performing day 2 or 3 embryo transfer.
√ cases of Preimplantation Genetic Diagnosis (P.G.D).