Preimplantation Genetic Testing for Structural Rearrangements (PGT-SR)

Preimplantation Genetic Testing for Structural Rearrangements (PGT-SR)

PGT-SR

Purpose : To identify embryos with structural chromosomal rearrangements before implantation.
Process : A biopsy of 4-8 trophectoderm cells is taken from the blastocyst on days 5, 6, or 7 of development.
Conditions detected : Inversion, reciprocal translocation, Robertsonian translocation.
Benefits : Increases the chances of successful implantation and reduces the risk of pregnancy loss and having a child with an unbalanced form of the rearrangement.

Additional Information

PGT-SR is often used in conjunction with IVF or ICSI.
The decision to undergo PGT-SR is a personal one and should be discussed with a healthcare provider.
Individuals with balanced translocations may have difficulty conceiving or experience recurrent pregnancy loss.
PGT-SR can help identify embryos that are euploid (without chromosomal abnormalities) or have a balanced form of the rearrangement, which is typically phenotypically healthy.

The three most common chromosome rearrangements include:

Balanced Translocation
This occurs when fragments from two different chromosomes break off and exchange places. Importantly, no genetic material is lost or gained in the process; only its distribution is altered. As a result, the overall amount of genetic material remains unchanged.

Unbalanced Translocation
This type of translocation results in an unequal exchange of genetic material between chromosomes, leading to a gain or loss of genetic segments. This imbalance can manifest in physical abnormalities and may cause various disease symptoms due to the altered genetic makeup.

Robertsonian Translocation
A specific and the most common type of unbalanced translocation in humans, involving chromosomes 13, 14, 15, 21, and 22. In this translocation, an entire chromosome from one pair fuses with another chromosome from a different pair, resulting in the loss of a small number of genes. However, because these lost genes are typically present in multiple copies on other chromosomes, this translocation generally does not affect physical appearance or cause disease symptoms.

PGT – SR Workflow

When Should a Biopsy Be Performed?

Embryo biopsies can be conducted on Day 3 (Blastomere) or Day 5 (Trophectoderm) of development. For Preimplantation Genetic Testing for Aneuploidy (PGT-A), a Day 5 biopsy is generally preferred due to several key advantages:

Enhanced Accuracy : By Day 5, there are more cells available, providing a larger DNA sample, which improves the precision of the test.
Mosaicism Detection : This stage allows for the identification of mosaicism in aneuploidies, resulting in more reliable outcomes.
Optimal Timing for Transfer : After the biopsy, embryos can be quickly frozen (vitrified), giving clinicians the flexibility to choose the best conditions for implantation in future cycles.

Technology We Use

MicroGen PGT utilizes advanced Next Generation Sequencing (NGS) technology to provide accurate and reliable genetic testing of embryos.