Blastomere biopsy (also known as embryo biopsy) is a technique that is performed during IVF when an embryo has reached the six to eight cell stage (about 72 hours or day 3 of embryo culture). One or two cells, or blastomeres, are separated from the rest of the embryo and removed from the zona pellucida which is the shell surrounding the developing embryo. After removal of the cell(s), the developing embryo is placed back into the culture media and returned to the incubator where it can resume its normal growth and development. Preimplantation genetic diagnosis – PGD can be performed separately on the removed cell(s).
In this picture, you can see the aspiration pipette (the glass tube on the right) gently pulling the single blastomere off of an 8 cell embryo.
At this early point of embryo development, all of the cells should be identical and thus, removal of a cell from the embryo at this stage should not remove anything critical for normal development. An embryo should be able to compensate for the removed cell and should continue to divide following blastomere biopsy. However, well done study suggested that a biopsy performed at the blastomere stage was responsible for a decreased chance that the embryo would be able to implant into the uterus later. for this reason, blastomere biopsy is not typically used anymore.
After obtaining cells from the embryo, they can then be analyzed using a variety of different techniques. It doesn’t matter which of the eight cells was removed because as the embryo divides, each subsequent generation of cells contains exactly the same genetic information as the “parent” cell. This, each of the eight cells should be identical.