Pre-Implantation Genetic Diagnosis and Screening (PGD and PGS)
Pre-implantation genetic diagnosis (PGD) is a technique used in In Vitro Fertilization (IVF) which allows genetic evaluation of an embryo before transfer and subsequent implantation (hence the term, “preimplantation” genetic diagnosis). This technique involves the removal of a single cell from a 6-8 cell embryo. The cell is fixed and can be analyzed for genetic abnormalities. The embryos are allowed to grow to blastocyst (more advanced stage) and “normal” embryos are then transferred. Common indications for PGD include carriers of single-gene disorders such a cystic fibrosis, patients with a family or personal history of inheritable disorder, and carriers of abnormal chromosomes. Other patient groups that may benefit from PGD include recurrent pregnancy loss (RPL), increased reproductive age of the female partner, repeated implantation failure (i.e. multiple failed IVF cycles).
Potential limitations of this technology are:
Requires adequate numbers of embryos to allow blast transfer
Risk of no embryos for transfer
Low risk of damage to the embryo during biopsy