Preimplantation genetic diagnosis, involves removing a cell from an IVF embryo to test it for a specific genetic condition before transferring the embryo to the uterus. It is considered as an alternative to prenatal screening.
Pre-Implantation Genetic Diagnosis is recommended when:
- Previous birth of a child with a single gene disorder, such as Cystic Fibrosis, Tay Sachs, Muscular Dystrophy, Hemophilia, Thalassemia, fragile X or Sickle cell.
- Both partners are “carriers” for a single gene disorder based on screening tests and, therefore, at risk for passing on inherited genetic disease to their offspring.
When is it done?
PGD is done when an embryo becomes a blastocyst which normally has more than 100 cells five days after fertilization, two or more cells are biopsied from the blastocyst, or it can also be done by taking one or two cells from an 8-cells embryo.
Genetic analysis is then performed on the cells that are obtained, to see whether the embryo contains the abnormal gene or chromosome. Those embryos or blastocysts that are chromosomally or genetically abnormal will not be transferred and allowed to perish. The embryos or blastocyst with normal gene will be transferred back into the uterus and allowed to implant and develop.