What is PGD?

Answer 1

Pre-implantation genetic diagnosis (PGD) is an alternative to prenatal diagnosis, in which genetic testing is performed on embryos produced by In Vitro Fertilization (IVF) before a clinical pregnancy is established. PGD has been mostly applied to woman of advanced maternal age undergoing IVF in order to increase implantation rates, to reduce spontaneous abortions and to reduce trisomies such as Downs Syndrome. This latter type of PGD is called aneuploidy screening. PGD has also been applied to chromosomal disorders, such translocations, in which it has proven to decrease the number of spontaneous abortions while preventing the conception of affected babies. The number of single gene disorders that have been diagnosed by PGD continues to grow. The most common ones include Cystic fibrosis, fragile X, Myotonic Dystrophy, Thalasaemia and Tay Sachs.

PGD usually requires that the couple undergo In Vitro Fertilization (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 transferred to an incubator. After three days the embryos usually consist of a tiny ball of eight cells, known as blastomeres. One to two embryo cells (blastomeres) are then removed (biopsied) from each embryo and subjected to genetic testing. If the blastomere is found to be unaffected by the inherited disease then the embryo that it was removed from should also be unaffected. Embryos that are revealed to be healthy can be transferred to the uterus, ultimately producing unaffected babies.

Preimplantation genetic diagnosis (PGD) is an alternative to prenatal diagnosis for people at risk of passing on an inherited disease to their children. The main benefit of PGD is that it maximizes the chance that a couple will have an unaffected pregnancy, greatly reducing the possibility that they will have to contemplate pregnancy termination.