Preimplantation Genetic Screening and Diagnosis (PGS/PGD) both involve testing embryos for genetic or chromosomal disorders. Both tests are conducted at the embryo stage, and require an analysis of cells. Biopsies are conducted on the embryos at the blastocyst stage (day 5), taking a sample of cells from the trophectoderm, which is a precursor to the placenta. The remaining cells of the embryo are left unharmed. Typically, the embryo is then frozen for future transfer, and will not be thawed until results can be reviewed by both the physician and patient.
PGS is a screening of the number of chromosomes found in the embryo. Essentially, it alerts us to chromosomal disorders such as Down’s syndrome or Edward’s syndrome.
PGD is a test to evaluate single gene disorders in the embryo. Single gene disorders include: cystic fibrosis, hemophilia, Huntington’s disease, Marfan’s disease, muscular dystrophy, thalassemia, Tay Sachs, spinal muscular atrophy, and sickle cell anemia to name a few.