Preimplantation genetic testing for aneuploidy (PGT-A) is a genetic analysis technique that is performed  on embryos before implantation in order to detect chromosomal alterations, especially aneuploidies, and support the selection of embryos with normal chromosomal status. On day 5 or 6 of embryo development, cells are removed by embryo biopsy, and the embryo is then vitrified until the test results are obtained.