Blastocyst is the technical term for the development stage of the embryo on the fifth day after fertilisation of the egg. In natural fertilisation, this is the stage during which the embryo arrives in the uterus after developing and moving through the fallopian tube.
Generally, after IVF or ICSI, embryo transfer takes place on the second or third day of development. However, today it is possible to culture embryos in an incubator for five days, until they reach the blastocyst stage. The hope is to select vital embryos more capable of implantation, as not all fertilised eggs will actually reach this stage.
Despite reports to the contrary, the culture and transfer of blastocysts is possible in Germany. In terms of the German Embryo Protection Act, it is only the stockpiling of blastocysts for selection and thus the production of an excessive number of embryos that is problematic.
In our experience, blastocyst culture is only beneficial for patients with favourable conditions (depending on age at the time of treatment and the number of fertilised eggs). With extended culture, particularly good pregnancy rates can be achieved after the first transfer for couples with several embryos, owing to the improved selection of embryos with the best potential for implantation. We can observe the development of embryos using time-lapse monitoring.
At FCH, we prefer to make a decision for or against the transfer of blastocysts on an individual basis after evaluating the situation of the couple in question.