What is a blastocyst ?
A blastocyst is a preimplantation embryo and can be considered as the last stage of embryonic growth, which can be cultured outside the body. After this stage, the embryo requires uterus to grow into a human being. It has 30-200 cells in it and has two distinct types of cells unlike only one type of cell in early cleavage stage embryos (from 2-32 cell). The two distinct cell types of a blastocyst are- the inner cell mass which, after implantation gets converted into the fetus and, trophoectoderm., which becomes the placenta
Until Recently, it was a common practice of almost all IVF centers to transfer embryos at the cleaving preembryo stage (usually 4-16 cells). This required culture of the embryos for 2-3 days in the laboratory. Recent development of advanced sequential culture media have allowed embryos to be cultured for 5-6 days so that they can reach to blastocyst stage
What are advantages of blastocyst culture?
Extended embryo culture in IVF theoretically allows the identification of those embryos with the highest developmental competence. It also helps in synchronizing embryonic age with endometrium to facilitate early communication between the two. This technique involves more than a single culture medium in order to accommodate the metabolic needs of the growing embryo. At present, the blastocyst formation rate per fertilized oocyte is in the range of 30-40 %. Other benefits include-
Are there any drawbacks of blastocyst transfer?
Blastocyst culture is a promising concept but it has to be carefully applied to the existing IVF set up. A sudden changeover to Day 5 transfer may not fulfill the expectations. Like ICSI, its application should be decided on patient-to-patient basis and should not be generalized to all, to avoid disappointments. A more detail information about the out come of blastocyst transfer from all centers will provide helpful guidelines for the most effective use of this concept.