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Preimplantation Genetic Diagnosis (PGD) and Preimplantation Genetic Screening (PGS) refers to procedures that are performed on embryos to identify specific genetic disease or abnormal chromosome numbers, prior to those embryos being placed back inside the uterus. PGD and PGS are only performed during an in vitro fertilization (IVF) cycle.
The term preimplantation genetic diagnosis (PGD) refers to a technique of looking for single gene disorders. Single gene disorders are specific mutations on chromosomes that cause certain diseases or conditions. Single gene disorders include autosomal recessive, autosomal dominant, X-linked disorders or a chromosomal structural aberration (such as a balanced translocation). The most frequently diagnosed autosomal recessive disorders are cystic fibrosis, Beta-thalassemia, sickle cell disease and spinal muscular atrophy type 1. The most common dominant diseases are myotonic dystrophy, Huntington's disease and Charcot-Marie-Tooth disease. In the case of the X-linked diseases, most of the cycles are performed for fragile X syndrome, haemophilia A and Duchenne muscular dystrophy.
The term preimplantation genetic screening (PGS) is used to denote procedures that do not look for a specific disease but use PGD techniques to identify embryos with aneuploidy (abnormal chromosome numbers).
Currently, all PGD and PGS embryos are obtained by assisted reproductive technology. In order to obtain a large group of oocytes (eggs), patients undergo controlled ovarian stimulation (COH). Eggs are retrieved and fertilized. The resulting embryos are biopsied on a specific day and genetic tests are performed on the biopsy to identify the single gene disorder or to evaluate the chromosomes.
At RMI, we use Gene Security Network to perform the analysis on the embryo biopsies. Please see their website for more details about PGD and PGS.
If you are interested in PGD or PGS, please contact RMI to schedule a consult.