Preimplantation Genetic Diagnosis (PGD)
Preimplantation Genetic Diagnosis or Preimplantation Genetic Testing
Preimplantation Genetic Diagnosis (PGD) , which at present is called Preimplantation genetic testing (PGT), involves screening cells from embryos for genetic diseases and chromosomal disorders. This testing is performed when an In-Vitro Fertilization (IVF) is performed and it takes place prior to embryo transfer, This allows doctors to transfer of only genetically healthy embryos.
How is DPG or PGT performed?
Technically, to perform PGT we need to perform an embryo biopsy. An embryo biopsy removes about 3-8 cells from each day 5 embryo (an embryo that has reached blastocyst stage). Then these cells are sent to a lab for testing. Sometimes (although very rearely) the biopsy is performed on day 3. The embryo is frozen while its cells are being evaluated, and implanted once the tests are back and the embryo is considered to be healthy.
Experienced embryologists perform the biopsy because it is important to avoid hurting the embryo. At ProcreaTec we almost always perform biopsies on day 5, at the blastocyst stage, which allows us to obtain more cells than on day 3. We only biopsy the strongest and most viable embryos that get to day 5.
When is a genetic study recommended?
- Early onset major hereditary diseases that are not susceptible to a postnatal cure. This is the case of couples that are both carriers of a mutation such as Cystic Fibrosis or when one of the parents has a monogenic disease like Neurofibromatosis.
- Determination of histocompatibility antigens (HLA) of preembyos with the objective of treating a sibling. When a couple has a child that has a disease that requires an umbilical cord transfusion or a bone marrow transplant healthy embryos that are genetically compatible with its sibling are sought after to be able to be a donor in the future.
- Anomalies that can compromise the viability of the preembryo. This is the case of repeated pregnancy loss,implantation failure and advanced maternal age, where numerical or structural anomalies of the embryo’s chromosomes (PGS: Preimplantation Genetic Screening) are looked for as the causes for these miscarriages.
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