Pre-Implantation Genetic Testing
Pre-implantation genetic testing is comprised of both Pre-implantation Genetic Diagnosis (PGD) and Pre-implantation Genetic Screening (PGS). PGD is the diagnosis of single gene disorders (most commonly, Cystic fibrosis, fragile X, Myotonic Dystrophy, Thalasaemia and Tay Sachs ) and translocations (chromosome rearrangements) PGS on the other hand, is the screening of chromosome copy number, referred to as aneuploidy. PGS is mostly applied to women of advanced maternal age or women with a previous history of miscarriages. Research indicates that utilizing PGS while undergoing IVF increases implantation rates, reduces spontaneous abortions (miscarriages) and reduces live births with abnormal chromosome numbers, such as Downs Syndrome.
PGD and PGS require the couple to undergo an IVF treatment. This involves hormonal treatments that allow the collection of multiple eggs from the mother. The eggs are then fertilized using the father’s sperm and the resulting embryos are placed in an incubator. After five days, the embryos should be at a stage of development called the blastocyst. A laser is used to biopsy off a small portion of the trophoblast, (the area that will become the placenta). These biopsied cells are then sent out to a genetic testing facility and the embryo itself is frozen while we await results. Embryos that are revealed to be normal can be transferred to the uterus during a thaw cycle.
The main benefit of PGD is the elimination of inherited diseases from the family, while PGS is utilized to maximize a patient’s chances of pregnancy while minimizing the chances of a miscarriage.