Genetic Testing of IVF Embryos: What is PGT and Who is it Recommended For?

Genetic testing of embryos in the context of in vitro fertilization (IVF) has become a powerful tool for improving the success of procedures, including the likelihood of pregnancy and the birth of a healthy child, as well as for reducing the risks of complications such as miscarriages and genetic abnormalities. This technology allows for a more accurate assessment of embryo quality at the genetic level, which is especially important for couples facing reproductive failures. In this article, we will delve into the advantages of PGT, its process, potential risks, and the necessity of its application in various clinical situations to help patients make an informed decision.

What is PGT?

Preimplantation Genetic Testing (PGT) is a specialized method of genetic diagnostics performed on embryos obtained through IVF, aimed at identifying chromosomal or genetic abnormalities before their transfer to the uterus. According to the definition by the American Society for Reproductive Medicine (ASRM, 2018), PGT is an evolution of preimplantation genetic diagnosis (PGD), first described by Handyside et al. in 1990, which allows for the analysis of embryonic genetic material to prevent the transmission of hereditary diseases.

PGT is not a separate IVF procedure but is integrated into it as an additional testing stage that can be selected based on medical indications. This distinguishes it from basic IVF, where embryo selection is often based on morphological criteria, while PGT adds genetic analysis to enhance selection accuracy.

There are three main types of PGT, each focusing on specific aspects of genetics, helping to minimize potential risks for the mother and future child:

• PGT-A (Aneuploidy Testing): Assesses the number of chromosomes in embryo cells, detecting aneuploidy — a condition where the number of chromosomes may be more or less than normal. This is particularly relevant for women of advanced reproductive age, as aneuploidy can increase the likelihood of spontaneous pregnancy termination or the birth of a child with chromosomal syndromes, such as trisomy 21 (Down syndrome). Testing helps select embryos with a normal chromosomal set, reducing associated risks.
• PGT-M (Monogenic Disease Testing): Aimed at detecting mutations in specific genes responsible for hereditary diseases, such as cystic fibrosis or thalassemia. If there is a family history of such conditions, PGT-M allows for the selection of embryos without these mutations, thereby preventing disease transmission and potential health complications for the child.
• PGT-SR (Structural Rearrangement Testing): Identifies abnormalities in chromosome structure, such as translocations or inversions, which can lead to implantation failures or recurrent miscarriages. This type is helpful in cases where parents have identified chromosomal rearrangements, reducing the likelihood of adverse outcomes.

Overall, PGT facilitates the selection of embryos with the greatest potential for successful development, which can improve the overall effectiveness of IVF without focusing on “ideality,” but on genetic stability.

How is PGT Performed?

PGT is fully integrated into the standard IVF cycle as an additional testing method, not replacing the main stages of the procedure, but supplementing them with genetic analysis. This allows doctors to obtain more comprehensive information about the embryos, increasing the chances of a favorable outcome without significantly prolonging the overall process.

Here is a detailed process of performing PGT:

1. Ovarian Stimulation and Egg Retrieval: Medication stimulation is aimed at producing several mature eggs, which are retrieved under ultrasound guidance in outpatient settings. This stage requires careful monitoring to minimize risks of hyperstimulation.
2. Fertilization and Embryo Culture: Eggs are fertilized with the partner’s or donor’s sperm in laboratory conditions, after which embryos are cultured in an incubator until they reach a suitable developmental stage.
3. Embryo Biopsy: On day 5–6 of culture, when the embryo forms a blastocyst (a structure of approximately 100–200 cells with an inner cell mass and an outer layer — trophectoderm), a biopsy is performed. Using laser or mechanical techniques, 3–5 cells are extracted from the trophectoderm, which does not affect the embryo’s viability, as these cells do not form the future fetus.
4. Genetic Analysis: The extracted cells undergo laboratory testing using modern methods such as next-generation sequencing (NGS), which allows for a detailed study of DNA for abnormalities. Results are usually ready within a few days.
5. Embryo Selection and Transfer: Based on the analysis, embryos with normal genetic characteristics are selected for transfer to the uterus or cryopreservation (freezing) for future cycles.

The integration of PGT adds about 1–2 weeks to the IVF cycle, mainly related to waiting for analysis results, but the biopsy procedure itself is minimally invasive and performed under a microscope in sterile conditions. The effectiveness of testing largely depends on individual factors such as the patient’s age and the quality of biological material, as well as the level of equipment and laboratory expertise.

Who is PGT Recommended For?

PGT can be a valuable addition to IVF not for all patients, but it is particularly relevant in situations where there are elevated genetic risks, helping to optimize the chances of a healthy pregnancy.

Consider the possibility of using PGT in the following cases:

• Women of Advanced Reproductive Age (Over 35 Years): With age, the likelihood of chromosomal abnormalities in eggs increases, which can lead to aneuploidy and, consequently, a higher risk of miscarriages or chromosomal syndromes in the fetus. PGT-A allows for the early detection of such embryos, promoting a more stable pregnancy course.
• Couples with a Family History of Genetic Diseases: If parents or relatives have been diagnosed with monogenic disorders (e.g., mutations in BRCA genes increasing the risk of oncological diseases), PGT-M helps select embryos without these mutations, reducing the likelihood of transmission.
• Patients with Recurrent Miscarriages or Failed IVF Cycles: In such situations, PGT can identify hidden genetic causes, such as chromosomal imbalances, and assist in selecting more promising embryos.
• Cases of Male Factor Infertility: In cases of spermatogenesis disorders, including low sperm quality, PGT contributes to assessing the genetic stability of embryos, minimizing failure risks.
• Carrier Couples for Recessive Genetic Diseases: If screening shows that both partners are carriers (e.g., of hemophilia or spinal muscular atrophy), PGT prevents the birth of a child with the disease manifestation.

At the same time, PGT is not mandatory for couples without identified risks, as its application should be justified by medical data. The decision on testing is always made individually after a thorough consultation with a reproductive specialist.

Advantages and Risks of PGT

Advantages:

• Increased Likelihood of Successful Implantation: Studies show that transferring embryos with a normal chromosomal set (euploid) can raise pregnancy chances to 60–70% per cycle, compared to basic IVF.
• Reduced Risk of Spontaneous Pregnancy Termination: Selecting embryos without aneuploidy decreases the likelihood of miscarriages, which is especially important for patients with a history of losses.
• Prevention of Genetic Diseases: PGT allows avoiding the transmission of hereditary conditions, providing greater peace of mind for future parents and potentially reducing medical complications in pregnancy.
• Possibility of Ethical Selection: In some cases, testing includes information about the embryo’s sex, but in many countries this is strictly regulated by ethical norms and applied only for medical indications.

Risks:

• Possible Inaccuracies in Results: Due to the phenomenon of mosaicism (when an embryo contains both normal and abnormal cells), the analysis may yield ambiguous data requiring additional interpretation; the accuracy of methods like NGS reaches 95–98%, but is not absolute (according to ESHRE data, 2020).
• Minimal Risk to the Embryo: Biopsy is performed at an early stage and rarely (less than 1% of cases) affects development, but in individual situations may reduce viability; modern techniques minimize this.
• Ethical Aspects: Testing raises questions about selection, but it is oriented solely on health, without interfering in “designer” children, and is regulated by international recommendations.
• Lack of Full Guarantee: Even genetically normal embryos do not always lead to a successful pregnancy, as outcomes are influenced by other factors, such as endometrial condition.

Scientific data, including meta-analyses from Cochrane (2021), confirm that the advantages of PGT outweigh the risks in high-risk groups, but its application should be balanced.

Conclusion: The Role of PGT in Modern IVF

Preimplantation genetic testing represents a significant advancement in reproductive medicine, providing detailed embryo analysis and contributing to increased chances of a healthy pregnancy with minimal risks. Based on accumulated scientific data, PGT is particularly effective in cases with genetic risk factors, helping couples make informed decisions. However, its use should always be part of a comprehensive approach, taking into account individual patient characteristics.

For a personalized consultation and discussion of PGT possibilities in your case, we invite you to schedule an appointment at the office of Irina Ivanovna Ergul — an experienced reproductive medicine specialist, member of the European Society of Human Reproduction and Embryology (ESHRE), who recently attended the international conference of this organization in Paris.

Reference

• Handyside, A. H., et al. (1990). “Pregnancies from biopsied human preimplantation embryos sexed by Y-specific DNA amplification.” Nature, 344(6268), 768-770.
• American Society for Reproductive Medicine (ASRM). (2018). “Preimplantation genetic testing: a Practice Committee opinion.” Fertility and Sterility, 109(3), 429-436.
• European Society of Human Reproduction and Embryology (ESHRE). (2020). “Good practice recommendations for the use of PGT.” Human Reproduction Open, 2020(4), hoaa033.
• Cochrane Review. (2021). “Preimplantation genetic testing for aneuploidy in in vitro fertilisation.” Cochrane Database of Systematic Reviews, Issue 5. CD013109.
• European Society of Human Reproduction and Embryology (ESHRE). (2024). “Updated guidelines on preimplantation genetic testing.” Human Reproduction, 39(1), 1-15.
• Munné, S., et al. (2024). “Recent advances in PGT-A and mosaicism management in IVF cycles.” Fertility and Sterility, 121(5), 789-802.
• ESHRE PGT Consortium. (2025). “Evidence-based recommendations for PGT in high-risk populations.” Human Reproduction Open, 2025(1), hoae001 (in press).