What is PGT?
The previous term preimplantation genetic diagnosis (PGD) and preimplantation genetic screening (PGS) has been replaced by the term preimplantation genetic testing (PGT).
PGT is defined as a genetic test that analyzes a DNA molecule from the oocyte (polar body) or embryo stage (morula or blastocyst stage) for HLA typing or for the determination of a genetic abnormality.
In relation to which aberrations we want to detect and determine PGT can be divided into three subgroups:
- PGT-A on aneuploidy
- PGT-M, on monogenic abnormalities (single gen defects)
- PGT-SR, on chromosomal structural rearrangement, PGT for chromosomal numerical aberrations that carry high genetic risk also belongs to the group of PGT-SR
This subgroup of PGT involves the testing of DNA of pathological variants caused by monogenic diseases, X-linked diseases and autosomal dominant or recessively inherited diseases.
The locus on mitochondria or nucleolus or HLA typing is analyzed.
Who is recommended for?
PGT-M is recommended for pathogenic germ lines of a genetic variant with a high probability of causing a disease with serious health consequences, during birth, childhood or adulthood. PGT-M should not be done in hereditary variants that will not cause disease sometime in life, in variants that are not clearly hereditary. PGT-M is also recommended for autosomal recessive anomalies when one parent is a carrier, for diseases that manifest later in life and there is a family heredity such as e.g. Huntington's disease.
PGT-SR is a generally accepted, routine procedure in most IVF centers, and analyzes the chromosomal status of embryos for targeted numerical or structural aberrations.
Who is recommended for?
It is recommended for patients who cannot have a pregnancy, have a high risk of miscarriage, and the birth of a child with major chromosopathies. The cause of this condition in the patient may be due to heredity or incorrect rearrangement of chromosome pairs during meiotic division.
Various techniques (FISH, quantitative real-time PCR) and methods (Acgh, snp, NGS, etc.) of analysis are available today.
Of all the available genetic preimplantation analyzes, PGT for anuplodia occupies the place where discussions in clinical practice are the most frequent so far. Aneuploidy is considered to be one of the leading causes of IVF / ICSI failure. For this reason, many doctors and fertility experts promote and recommend PGT-A as a solution.
An IVF specialist may suggest PGT-A in the case of:
- Age of mother
- More failed implants
- Frequent abortions
Certainly, the advice for all those who opt for PGT-A as a solution to the problem of marital infertility is to first analyze the karyotype of both spouses, due to the greater possibility that one of the partners has a structural chromosome re-emergence.
Is PGT analysis for me?
When we think of PGT as a solution in the fight against marital infertility, we must first exclude the basic criteria that led to marital infertility, such as: woman's age, inability to obtain quality male and female gametes, obesity, etc. PGT should also be taken with caution when a woman has clear signs and symptoms of autosomal dominant or X-linked disease, and may worsen her mental and physical condition.
The recommendation on genetic analysis of embryos for some diseases should be made by the professional team of the IVF center together with patients, and put the patient's needs first and their decisions, concisely and clearly explain what the result of their testing means, what are their further possibilities. The analysis itself implies the correlation and active cooperation of several experts from a clinical embryologist, a genetic laboratory, a leading doctor to a psychologist who will be available to patients.