Preimplantation genetic diagnosis (PGD) is considered a complementary technique to in vitro fertilisation (IVF), as it is not possible with artificial insemination (AI). PGD is most commonly performed using embryos at day 3 of development. This way, taking a cell from the embryo when it contains 8 cells does not affect its viability.
The results of PGD will provide information about which embryos are healthy, i.e. have no genetic alterations, and which embryos are diseased. From the genetically healthy embryos, the best one will be selected for transfer and the rest will be vitrified for future transfers. On the other hand, genetically altered embryos are discarded and cannot be transferred.