Should we test embryos before transfer?

What is PGT?

PGT stands for Preimplantation Genetic Testing — a group of tests performed on embryos prior to transfer in order to detect genetic or chromosomal abnormalities.

There are three main types of PGT:
- PGT-A — for the detection of aneuploidies (chromosomal errors in the number);
- PGT-SR — for structural chromosomal rearrangements;
- PGT-M — for monogenic (hereditary) diseases.

What does PGT-A (Aneuploidy Screening) detect?

It checks whether the embryo has the correct number of chromosomes (46). Detects trisomies, monosomes and other chromosomal abnormalities, which often lead to:
- unsuccessful implantation;
- miscarriage;
- congenital abnormalities (eg Down syndrome).

When is it recommended?

It is recommended for:

- Women over 35—37 years old;
- Repeated miscarriages;
- More than 2 unsuccessful IVF attempts;
- Male factor with severe DNA fragmentation;
- When there are many embryos and we are looking for the one with the highest chance.

What does PGT-SR (Structural Rearrangements) detect?

PGT-SR looks for chromosome rearrangements — e.g., translocations, inversions, and deletions. In some patients with normal appearance and state of health, there may be a balanced chromosomal abnormality that does not directly affect them, but is transmitted to the embryos.

When is it recommended?

- With proven balanced translocation in one partner (from karyotype);
- After multiple unsuccessful transfers or abortions for no other reason;
- In congenital abnormalities in the family history.

What does PGT-M (Monogenic Disorders) detect?

This test is applied when there is a risk of transmitting a particular genetic disease associated with a mutation in one gene. Unlike PGT-A, it looks for a specific mutation that the parents carry.

Some of the most common diseases in which it is applied are:
- Thalassemia;
- Cystic fibrosis;
- Spinal muscular atrophy (SMA);
- Hemophilia;
- Neurofibromatosis;
- Hereditary forms of cancer (BRCA, Lynch, etc.).

How is it carried out?

It requires a preliminary molecular analysis of the parents and often of other relatives. The preparation procedure can take 6—8 weeks. Then a personalized test is worked out for each specific case.

When is it recommended?

- If both partners are carriers of the same recessive disease;
- If one partner is affected or carries a dominant mutation;
- If there are affected children in the family.

How does the procedure itself go?

1. Embryos are cultured until day 5—6 (blastocyst stage);
2. Several cells of the trophectoderm are taken from them;
3. The embryo is frozen;
4. Cells are sent to a genetic laboratory;
5. After 1—3 weeks, the results are received and a transfer of a genetically normal embryo is planned.

Advantages of PGT tests

- Higher chance of successful transfer
- Lower risk of miscarriage
- The opportunity to give birth to a healthy child without hereditary disease
- Fewer failed cycles and better treatment planning

Are there any disadvantages or limitations?

- Does not guarantee pregnancy, even with a normal result;
- Increases the cost of the IVF procedure;
- Requires a high level of laboratory competence;
- With PGT-M, time is required to build a specific test;
- In rare cases, there may be mosaicism of the embryo - cells with different genetic composition.

Conclusion

PGT isn't for everyone — but when there are indications, it's a powerful tool that can save time, effort, and emotional exhaustion. In our clinic, we approach each couple individually and discuss together whether and what genetic testing would be appropriate.
Because sometimes knowing more about your embryo means taking a safer step towards a healthy baby.

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