Preimplantation genetic diagnosis (PGD) is a process that involves the genetic testing of embryos, following a selective transfer of genetically normal embryos. PGD is used to perform preimplantation genetic screening (PGS) for couples who have a high risk of carrying a child with a genetic disorder. These disorders can happen if the mother is considerably older to have a baby, and experience repeated IVF-failures with an unfortunate amount of miscarriages and non-obstructive azoospermia.
You will find that common genetic diseases can be prevented through PGD/PGS include any chromosomal abnormalities (e.g. Down Syndrome), Thalassemia, Cystic Fibrosis, Fragile X syndrome, X-Linked disorders, etc.
So how does PGD work? This process removes a single blastomere from a day 3 embryo following its genetic testing. Blastomeres are otherwise known as single cells that become analyzed by a new molecular cytogenetic method called array-CGH. This allows for simultaneous analysis towards the entire chromosome complement.
A blastocyst biopsy can be an alternative to a day 3 biopsy if you would prefer another method. The procedure can only be performed on high-quality blastocysts that have been self-correct and undertook the first cellular differentiation. Blastocyst screening can only be coupled with cryopreservation, as it involves the freezing of the blastocysts in order to allow for the array-CGH analysis to happen.