Preimplantation Genetic Diagnosis
What is PGD?
Preimplantation genetic diagnosis (PGD) is a method to assess the genetic health of embryos created in an IVF cycle. After eggs are fertilized with sperm and develop into embryos with at least 8 cells, one of the cells from each embryo is removed under a microscope, and the chromosomes of that cell is analyzed to determine whether the embryo is genetically normal or not.
Who benefits from PGD?
There are a number of genetic diseases and chromosomal abnormalities that can be detected by PGD. Thus, PGD benefits patients who are carriers of genetic diseases and prevent the diseases from being expressed in their children and parents who want to avoid having chromosomal abnormalities in children. A common example of chromosomal abnormalities that can be detected by PGD is Down’s syndrome. In a more complicated process, PGD can pick up inherited genetic diseases like Tay-Sachs disease, Cystic Fibrosis, Sickle Cell disease, Huntington's Chorea disease, Cooley's Anemia, and many others.
In addition, PGD is also used in gender selection processes, where parents who want to have a child of a specific gender have only embryos of the desired gender transferred to the uterus. In contrast to gender selection methods based on sorting of sperm (between those with X chromosome and those with Y), gender selection via PGD is nearly 100% accurate.
Risk of PGD
All embryos stay at CHR and are never shipped out. This ensures maximum safety and lowers the risk of mix-ups
PGD became widely available during the 1990s, but it was not until 2001 that the two professional organizations in the field, American Society for Reproductive Medicine (ASRM) and Society for Assisted Reproductive Technologies (SART) issued a statement declaring the procedure no longer experimental.
There are several risks involved in PGD, one of which is the possibility of false positive or false negative diagnosis. Cells that make up an early-stage embryo are not all identical (this is called mosaicism). Because of mosaicism, if a biopsied cell happened to contain an abnormal chromosome that is not present in other cells, this could result in a false positive diagnosis.
Embryos also have an ability to isolate and remove some of their genetically abnormal cells, meaning that even embryos that had chromosomally abnormal cell(s) at the time of PGD may correct themselves and grow into normal babies later on.
Long-term outcomes on offspring born after PGD have not been clearly defined. In addition, removal of a cell has a chance of damaging the embryo to a degree, resulting in lower pregnancy chances compared to non-PGDed embryos.
Norbert Gleicher, MD, leads CHR’s clinical and research efforts as Medical Director and Chief Scientist. A world-renowned specialist in reproductive endocrinology, Dr. Gleicher has published hundreds of peer-reviewed papers and lectured globally while keeping an active clinical career focused on ovarian aging, immunological issues and other difficult cases of infertility.