Preimplantation Genetic Testing for Monogenic or Single Gene Disorder (PGT- M)

Preimplantation genetic testing for a Monogenic or Single Gene Disorder(PGT‐M) is formerly known as Preimplantation genetic diagnosis (PGD). PGT-M is a diagnostic tool for detecting single-gene disorders in patients with a high risk of passing genetic abnormality to their children. This test helps to reduce the risk of having genetic diseases in children.

Also Read: What Is Preimplantation Genetic Testing (PGT) and How Does It Work?

This test helps couples in conceiving a healthy pregnancy. The procedure is performed before a female conceives. PGT- M:

• Examines the DNA of each embryo
• Recognizes the healthy embryo
• Assists the physician in deciding which embryo is suitable for transfer

PGT-M is recommended in:

• Fertile couples with a family history of a hereditary condition
• Couples who had a history of severe monogenic or single-gene disorder disorders (some common examples: Cystic Fibrosis, Spinal Muscular Dystrophies or SMA, Huntington Disease)

A genetic disorder results in an altered gene function by an altered DNA sequence (or, mutation).

• For a PGT-M, a set-up test is important. Each couple has its unique probe which is used to implement the test on embryos
• Blood samples are taken from the couple or their family members for building the probe.

This procedure includes testing embryos produced via IVF, selecting and transferring the ones with the correct amount of chromosomal material.

• A biopsy of the embryo is taken after it is grown in culture for about five days and reaches the blastocyst developmental stage made up of hundreds of cells.
• The biopsy involves the removal of 5 to 7 cells of the external layer of the embryo, called trophectoderm, without touching the inner cell mass that gives rise to the fetus.
• Analysis of the embryo’s genetic material is carried out.
• Embryos are cryopreserved following biopsy. The suitable embryos, based on the PGT-M results, are thawed and transferred to the patient’s uterus in a subsequent cycle.

Also Read: Frozen Embryo Transfer Procedure: All You Want to Know

It is safe to carry out PGT-M. The procedure needs to be handled by a skilled embryologist. Normal embryo development can be seen after the embryo biopsy.