PGT, preimplantation genetic testing, is a genetic test performed on embryos created through IVF to screen for chromosomal abnormalities.
- Preimplantation genetic testing for aneuploidy (PGT-A): Human embryos should have 23 pairs of chromosomes in each cell. One chromosome in each pair . It is not uncommon for embryos to have random chromosome abnormalities such as a missing or extra chromosome ,this is called aneuploidy. In the most cases, these chromosome abnormalities happen by chance and are not typically inherited from a parent Embryos with aneuploidy are more likely to result in miscarriage or a failed IVF cycle may result in Down syndrome or Turner syndrome. PGT-A is primarily designed to ensure an embryo has the correct number of chromosomes (euploidy). PGT-A screens embryos for whole missing chromosomes (monosomies) and whole extra chromosomes (trisomies). PGT-A also screens for missing or extra pieces of chromosomes (deletions or duplications, respectively). Deletions and duplications must be large to potentially be detected. Some, but not all, versions of PGT-A may detect additional types of chromosome abnormalities such as mosaicism and uniparental disomy
- Preimplantation genetic testing for monogenic disorders (PGT-M): PGT-M is appropriate when an individual is affected with a genetic condition that could be passed on to his or her children, for individuals who are carriers for an X-linked condition, or when an individual and their partner or donors are both carriers for the same autosomal recessive condition.
- Preimplantation genetic testing for structural rearrangements (PGT-SR): This type of PGT is performed when a patient or their partner has a rearrangement of their own chromosomes such as a translocation or inversion. A person with a translocation or inversion is at increased risk to produce embryos with missing or extra pieces of chromosomes. Embryos with missing or extra pieces of chromosomes are more likely to result in miscarriage or a child with serious health issues.
How is PGT sample collected?
The patient through their IVF and egg retrieval. Their embryos are monitored in IVF Lab until day 5 or 6 (Blastocysts). On day 5 few cells are biopsied from each embryos and are sent to lab for PGT testing . the cells are biopsied from Trophectoderm. These are expected to be representing the rest of the embryo,but not always. All the embryos are labeled and frozen separately after the biopsy and the results are awaited. It approximately takes21days for the results to come. The health embryos are thawed and transferred at a appropriate time . In some cases the embryos are biopsied on day 3 and quick run method of testing is used and the embryos are cultured meanwhile in the lab to Blastocyst stage and transfer is done on day 5 or day 6 .
Is PGT-a testing worth it?
PGT-A reduces the risk of having a child with a chromosomal abnormality. For women who have had unexplained miscarriages, PGT-A can reduce the risk of future miscarriages. PGT-A is expensive and is in addition to the costs of IVF. There is a possibility of false positive too in this test.The biopsy process, which removes cells from each embryo for PGT, has a small chance of damaging the embryo.
The cost of PGT
The cost of PGT is of a full cycle of IVF, charges for Biopsy of embryos , the testing charges plus freezing and in later date thawing and embryo transfer.