How is it performed?
PGD is performed with a biopsy in 1-2 embryonic cells (at the 8-cell stage, i.e. in a 3rd day embryo) cultured in the laboratory. At this stage, all 8 embryonic cells contain exactly the same genetic material. 1 – 2 cells are isolated for biopsy, while the remaining 6-7 cells continue growing. At this stage, embryonic cells are multipotent, i.e. no problem is caused by 1-2 cells being removed from the embryo; the remaining ones are capable of developing into a perfectly healthy embryo.
Biopsy is performed with the use of molecular biology techniques; this is exactly why PGD is costly. During the analysis, the embryo that undergoes biopsy continues being cultured in the laboratory (cell number increases) and keeps growing towards the blastocyst stage. As soon as the analysis is completed, healthy embryos are selected and transferred at the stage of embryo transfer.