PGT-A is performed on a few cells taken from the embryo. Hence, the biopsy procedure has two steps:
• the opening of the zona pellucida (outer shell of the embryo)
• removal of the cell(s).
The biopsy is performed either at the cleavage stage (day 3 of embryonic development) or the blastocyst stage (starting from day 5 of embryonic development). A 3-day old embryo has nearly 6 to 8 cells whereas a blastocyst has a few hundred cells. Therefore, several cells can be safely removed during the biopsy of a 5-, 6- or 7-day old embryo. The cells of the embryo will be tested using the NGS technique allowing comprehensive chromosome screening.