Preimplantation Genetic Diagnosis (PGD)
Preimplantation genetic diagnosis (PGD) involves the genetic testing of embryos followed by the selective transfer of genetically normal embryos.
PGD has also expanded to perform PGS (preimplantation genetic screening ), offered to couples with a high risk for a child with a genetic disorder such as in cases of advanced maternal age, repeated IVF failure, repeated miscarriages and non-obstructive azoospermia.
Common genetic diseases that can be prevented through PGD/PGS include any chromosomal abnormalities (e.g. Down syndrome), thalassemia, cystic fibrosis, fragile X syndrome, X-Linked disorders, etc.
Preimplantation Genetic Diagnosis involves the removal of a single blastomere from a day 3 cleavage embryo following its genetic testing. Blastomeres (single cells) are analyzed via a new molecular cytogenetic method called array-CGH, allowing simultaneous analysis of the entire chromosome complement.
Blastocyst biopsy is an increasingly attractive alternative to day-3 biopsy. Blastocyst biopsy is only performed on high quality blastocysts that have had the opportunity to self-correct and undertook the first cellular differentiation. Blastocyst screening, however, is coupled to cryopreservation as it requires freezing of the blastocysts in order to allow array-CGH analysis.