Pre-implantation genetic testing (PGT) is a procedure performed in the laboratory during an IVF cycle in order to detect abnormalities in the chromosomes of the embryos or to test the embryo before it implants for a specific, known genetic disorder, usually caused by a single gene abnormality. PGT involves removal of a cell or several cells from the embryo that has been formed in the laboratory from the union of sperm and egg during the IVF process. Under the microscope, the laboratory technician performs a biopsy of a day 5 or 6 embryo (blastocyst), and the cells that are removed are sent for genetic analysis at a special genetics laboratory off-site. The embryos are then frozen and stored (cryopreserved) in the IVF laboratory. Once the results are available, only genetically healthy embryos will be transferred into the uterus in the future.