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This report is written by MaltSci based on the latest literature and research findings

How does preimplantation genetic testing work? ​

Abstract ​

Preimplantation Genetic Testing (PGT) has emerged as a pivotal technology in reproductive medicine, enabling genetic analysis of embryos prior to implantation during in vitro fertilization (IVF). The rising prevalence of genetic disorders and the desire for healthy offspring have propelled the development and application of PGT, making it an essential component of assisted reproductive technologies (ART). This report provides a comprehensive overview of PGT, detailing its definition, purpose, and the three primary types: PGT for aneuploidy (PGT-A), PGT for monogenic disorders (PGT-M), and PGT for structural rearrangements (PGT-SR). The methodologies of PGT, including oocyte retrieval, embryo culture, and advanced genetic testing techniques such as next-generation sequencing (NGS) and polymerase chain reaction (PCR), are examined to elucidate their roles in enhancing IVF success rates and minimizing the risk of hereditary diseases. Furthermore, the clinical applications of PGT in preventing genetic disorders and improving reproductive outcomes are discussed, alongside the ethical implications associated with genetic selection. The report emphasizes the need for standardized protocols to address the ethical, legal, and societal concerns surrounding PGT. In conclusion, PGT serves as a crucial tool in modern reproductive health care, offering prospective parents the opportunity to make informed choices regarding embryo selection based on genetic testing, while also highlighting the importance of ongoing research and ethical considerations in shaping the future landscape of reproductive choices.

Outline ​

This report will discuss the following questions.

  • 1 Introduction
  • 2 Overview of Preimplantation Genetic Testing
    • 2.1 Definition and Purpose of PGT
    • 2.2 Types of PGT: PGT-A, PGT-M, and PGT-SR
  • 3 Methodologies of PGT
    • 3.1 Oocyte Retrieval and Embryo Culture
    • 3.2 Genetic Testing Techniques: NGS and PCR
  • 4 Clinical Applications of PGT
    • 4.1 PGT in Preventing Genetic Disorders
    • 4.2 PGT in IVF Success Rates
  • 5 Ethical Considerations
    • 5.1 Ethical Implications of Genetic Selection
    • 5.2 Psychological Impact on Parents and Society
  • 6 Future Directions in PGT
    • 6.1 Technological Advancements
    • 6.2 Expanding Access to PGT
  • 7 Conclusion

1 Introduction ​

Preimplantation Genetic Testing (PGT) has emerged as a transformative technology in reproductive medicine, enabling genetic analysis of embryos prior to implantation during in vitro fertilization (IVF). The escalating incidence of genetic disorders and the societal aspiration for healthy offspring have catalyzed the evolution and application of PGT, positioning it as a critical tool in assisted reproductive technologies (ART). The capability to screen embryos for specific genetic conditions before implantation not only enhances the likelihood of successful pregnancies but also minimizes the risk of hereditary diseases in future generations. This report aims to provide a comprehensive overview of the mechanisms and methodologies underlying PGT, its clinical applications, and the ethical implications surrounding its use.

Historically, PGT began as an experimental procedure in the 1990s, evolving into a standard practice in ART across many countries today[1]. Its primary purpose is to select embryos free from genetic abnormalities, thereby improving the success rates of IVF and reducing the incidence of genetic disorders[2]. The integration of advanced technologies such as next-generation sequencing (NGS) and polymerase chain reaction (PCR) has significantly enhanced the accuracy and reliability of genetic assessments, making PGT a vital component of modern reproductive health care[3].

Current literature reflects a growing body of evidence supporting the effectiveness of PGT in various clinical scenarios. For instance, PGT for aneuploidy (PGT-A) has been shown to improve implantation rates by enabling the selection of euploid embryos, while PGT for monogenic disorders (PGT-M) allows couples with known genetic conditions to prevent the transmission of these disorders to their offspring[4]. Moreover, the evolution of PGT techniques continues to unfold, with ongoing research exploring the implications of these advancements on reproductive choices and outcomes[5].

The organization of this report will follow a structured outline to systematically address the complexities of PGT. The first section will provide an overview of PGT, detailing its definition, purpose, and the three primary types: PGT-A, PGT-M, and PGT-SR. Following this, we will delve into the methodologies employed in PGT, focusing on oocyte retrieval, embryo culture, and the various genetic testing techniques utilized, including NGS and PCR. The clinical applications of PGT will then be examined, highlighting its role in preventing genetic disorders and enhancing IVF success rates. Ethical considerations will also be a focal point, discussing the implications of genetic selection and the psychological impacts on parents and society at large. Finally, we will explore future directions in PGT, emphasizing technological advancements and the need for expanding access to these vital reproductive technologies.

As the field of genetics and reproductive medicine continues to evolve, understanding the intricacies of PGT is crucial for practitioners and prospective parents alike. This report seeks to illuminate the multifaceted aspects of PGT, providing insights into its clinical relevance, ethical considerations, and the future landscape of reproductive choices in an increasingly complex genetic world.

2 Overview of Preimplantation Genetic Testing ​

2.1 Definition and Purpose of PGT ​

Preimplantation Genetic Testing (PGT) is a sophisticated diagnostic procedure utilized in the context of assisted reproductive technologies, such as in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI). The primary purpose of PGT is to identify genetic abnormalities in embryos prior to implantation, thereby allowing for the selection of embryos that are free from specific genetic conditions or chromosomal abnormalities. This process aims to enhance the success rates of reproductive cycles, minimize the risk of complicated pregnancies, and reduce the incidence of genetic diseases in offspring.

The procedure involves the biopsy of an early embryo created through IVF or ICSI, wherein a small number of cells are extracted from the embryo for genetic analysis. Following this biopsy, genetic testing is conducted to evaluate the genetic makeup of the embryos. This testing can identify chromosomal abnormalities, assist in the detection of monogenic disorders, and exclude structural rearrangements, which are critical in ensuring that only the healthiest embryos are selected for transfer into the uterus (Petch & Crosby, 2024; Kakourou et al., 2024).

The evolution of PGT has been significant since its inception in the 1990s. Initially regarded as an experimental procedure, it has now become an integral component of assisted human reproduction (AHR). Advances in genetic understanding, coupled with improvements in technology, particularly next-generation sequencing (NGS) and bioinformatics, have contributed to more accurate and efficient PGT processes. These advancements allow for the detection of a wider range of genetic issues, including complex findings such as mosaicism and variants of unknown significance, which require careful interpretation and counseling (Capalbo & Wells, 2025; Latham, 2024).

Despite its benefits, PGT is not without challenges. There are ongoing debates regarding its ethical implications, particularly concerning its application to late-onset disorders and non-medical uses such as sex selection. The need for standardized protocols and guidelines is essential to ensure the clinical value of PGT and to address ethical, legal, and societal concerns surrounding its use (Ginoza & Isasi, 2020; Lee et al., 2023).

In summary, PGT serves as a pivotal tool in modern reproductive medicine, enabling prospective parents to make informed choices about embryo selection based on genetic testing. Its continued development and integration into fertility care promise to enhance reproductive outcomes while necessitating ongoing dialogue regarding the ethical ramifications of its applications.

2.2 Types of PGT: PGT-A, PGT-M, and PGT-SR ​

Preimplantation genetic testing (PGT) is a sophisticated technique employed in assisted reproductive technology (ART) to assess genetic abnormalities in embryos created through in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI). This testing is crucial for couples seeking to improve their chances of having a healthy child while reducing the risk of genetic conditions. PGT has evolved significantly since its inception in the 1990s, becoming an integral part of reproductive medicine.

The primary types of PGT include:

  1. PGT for Aneuploidy (PGT-A): This form of testing evaluates embryos for chromosomal abnormalities, specifically aneuploidy, which is an abnormal number of chromosomes. By selecting euploid embryos (those with the correct number of chromosomes) for transfer, PGT-A aims to enhance implantation success rates and reduce the likelihood of miscarriage. Advances in technology, particularly Next Generation Sequencing (NGS), have improved the accuracy of PGT-A, allowing for better identification of viable embryos [2].

  2. PGT for Monogenic Conditions (PGT-M): This testing is designed to prevent the transmission of single-gene disorders. Couples with a known risk of passing on a genetic condition can use PGT-M to identify embryos that do not carry the genetic mutation associated with the disorder. Traditionally, this involves a biopsy of the embryo, followed by genetic analysis. Non-invasive approaches, such as analyzing cell-free DNA (cfDNA) from spent culture media, are being explored to minimize the risks associated with embryo biopsy [6].

  3. PGT for Structural Rearrangements (PGT-SR): This type of testing focuses on identifying chromosomal structural abnormalities, such as translocations or inversions, that may affect embryo viability or lead to genetic disorders. PGT-SR is particularly relevant for individuals with known chromosomal rearrangements who wish to ensure that their embryos are free from these abnormalities [6].

The process of PGT involves several critical steps. Initially, embryos are created through IVF or ICSI. After a few days of development, typically at the blastocyst stage, a small number of cells are biopsied from each embryo. The biopsied cells are then subjected to genetic testing, which can include methods like NGS to assess for aneuploidy or specific genetic conditions [1].

The results of the genetic testing guide clinicians in selecting the most viable embryos for transfer, thereby increasing the chances of a successful pregnancy and reducing the risk of genetic disorders in the offspring. However, the technology is not without limitations. Challenges such as the interpretation of mosaicism (the presence of both normal and abnormal cells in an embryo), variants of unknown significance, and ethical considerations regarding the implications of embryo selection are ongoing concerns in the field [4].

In summary, PGT is a powerful tool in reproductive medicine that encompasses various types, including PGT-A, PGT-M, and PGT-SR, each serving distinct purposes in genetic assessment. As technology continues to advance, the integration of methods like whole genome sequencing is expected to further enhance the capabilities of PGT, making it a cornerstone of reproductive healthcare [7][8].

3 Methodologies of PGT ​

3.1 Oocyte Retrieval and Embryo Culture ​

Preimplantation genetic testing (PGT) is a methodology aimed at assessing the genetic composition of embryos prior to implantation during in vitro fertilization (IVF). The primary objective of PGT is to select euploid embryos for transfer, thereby improving clinical outcomes such as embryo implantation rates, clinical pregnancy rates, and live birth rates[8].

The process of PGT begins with oocyte retrieval, where mature oocytes are collected from the ovaries of the female partner or a donor. The quality of the oocytes is crucial, as the maturity of the oocytes at the metaphase II stage is associated with higher fertilization rates compared to immature oocytes[9]. Following retrieval, the oocytes are fertilized, and the resulting embryos are cultured under controlled laboratory conditions.

Embryo culture typically progresses through several stages, including the cleavage stage and the blastocyst stage. Different sampling techniques can be employed at various stages of embryo development to perform genetic testing. For instance, polar body biopsy can be performed at the polar body stage, while trophectoderm biopsy is commonly conducted at the blastocyst stage, which is now considered the standard method for PGT[10].

The methodologies used in PGT have evolved significantly over the years. Initially, techniques such as fluorescence in situ hybridization (FISH) were utilized, but advancements have led to the adoption of next-generation sequencing (NGS), allowing for comprehensive analysis of multiple genetic abnormalities in a single biopsy[10]. These methods enable clinicians to assess the genetic status of embryos, identifying those that are euploid (normal chromosome number) and suitable for transfer while avoiding aneuploid embryos, which are associated with increased risks of miscarriage and developmental issues[11].

The clinical significance of PGT lies in its ability to evaluate embryo euploidy and mosaicism before transfer, thus enhancing the likelihood of successful pregnancies and reducing the incidence of genetic disorders in offspring[8]. Additionally, various non-invasive and invasive methods, including morphokinetics and proteomics, are being explored to further improve embryo selection strategies[9].

In summary, PGT involves a series of well-defined steps starting from oocyte retrieval, followed by embryo culture and genetic testing at critical developmental stages, utilizing advanced methodologies to ensure the selection of the most viable embryos for transfer.

3.2 Genetic Testing Techniques: NGS and PCR ​

Preimplantation Genetic Testing (PGT) is a sophisticated procedure employed in the context of assisted reproductive technologies, such as in vitro fertilization (IVF), to assess the genetic status of embryos before they are transferred to the uterus. The methodologies utilized in PGT have evolved significantly, particularly with the advent of advanced genetic testing techniques such as Next Generation Sequencing (NGS) and Polymerase Chain Reaction (PCR).

The process of PGT begins with the creation of embryos through IVF or intracytoplasmic sperm injection (ICSI). Once the embryos reach a suitable developmental stage, typically the blastocyst stage, a biopsy is performed to extract a small number of cells from the embryo. This biopsy can be performed on different embryonic stages, including polar bodies, cleavage embryos, or trophectoderm cells, each offering unique advantages and considerations in terms of the genetic information obtained[8].

Once the embryonic cells are collected, they undergo genetic testing. Two primary techniques used for this purpose are NGS and PCR:

  1. Next Generation Sequencing (NGS): NGS has revolutionized genetic testing by allowing for the simultaneous sequencing of millions of DNA fragments. This high-throughput technology enables comprehensive analysis of the entire genome or specific regions of interest, facilitating the detection of chromosomal abnormalities, single nucleotide variants, and even structural rearrangements. The ability to analyze large amounts of data quickly and accurately makes NGS particularly advantageous for PGT, as it can provide detailed insights into the genetic makeup of embryos[12].

  2. Polymerase Chain Reaction (PCR): PCR is a well-established technique that amplifies specific DNA sequences, making it easier to analyze smaller quantities of genetic material. In the context of PGT, PCR can be employed to identify known genetic mutations associated with specific inherited disorders. This technique is often used for targeted testing, where specific genes or mutations are of interest, allowing for precise evaluation of embryos for conditions such as cystic fibrosis or sickle cell anemia[5].

The choice between NGS and PCR often depends on the clinical context and the specific genetic conditions being assessed. While NGS provides a broader overview of the genetic landscape, PCR is beneficial for targeted analyses where specific genetic mutations are known.

Overall, the methodologies of PGT, incorporating advanced genetic testing techniques like NGS and PCR, are designed to enhance the accuracy of embryo selection, thereby improving the chances of successful implantation and reducing the risk of genetic diseases in offspring. However, as these technologies continue to evolve, ongoing research and ethical considerations will play a crucial role in shaping the future of PGT practices[2][4].

4 Clinical Applications of PGT ​

4.1 PGT in Preventing Genetic Disorders ​

Preimplantation Genetic Testing (PGT) is a sophisticated procedure utilized primarily in the context of Medically Assisted Reproduction (MAR) to identify genetic abnormalities in embryos prior to implantation. This technique is designed to ensure that only embryos free from specific genetic conditions or chromosomal abnormalities are selected for transfer, thereby minimizing the risk of unsuccessful MAR cycles, complicated pregnancies, and genetic diseases in future children [2].

The process of PGT begins with the creation of embryos through techniques such as in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI). Following fertilization, a biopsy is performed on the early embryo to obtain a small number of cells for genetic analysis. This genetic testing aims to identify any potential genetic disorders, enabling the selection of the healthiest embryos for transfer [1].

Initially, PGT was predominantly used for detecting monogenic diseases and chromosomal aneuploidies, significantly improving outcomes for couples facing infertility by reducing the risk of miscarriage and genetic disease [13]. However, advancements in genetic technologies have expanded its application to polygenic diseases, which are influenced by multiple genetic factors. The development of techniques for accurate genome-wide genotyping of human embryos and the establishment of population-level biobanks have made it feasible to assess the risk of polygenic diseases in embryos [13].

The clinical applications of PGT extend beyond simply identifying monogenic disorders. It plays a crucial role in preventing the transmission of inherited diseases by allowing for the selection of embryos that do not carry known genetic mutations. This is particularly significant for couples with a family history of genetic disorders, as PGT can reduce the likelihood of having a child affected by such conditions [7].

As PGT continues to evolve, the integration of advanced technologies such as Next Generation Sequencing (NGS) has enhanced its diagnostic accuracy. These advancements, however, come with challenges, including the interpretation of complex genetic findings such as mosaicism, mitochondrial DNA variants, and variants of unknown significance [2]. The necessity for standardized protocols and guidelines is emphasized to ensure the clinical value of PGT while addressing ethical, legal, and societal issues that arise from its application [2].

In summary, PGT functions by combining genetic analysis with reproductive technologies to identify and select embryos that are free from specific genetic abnormalities, thereby playing a pivotal role in preventing genetic disorders and improving reproductive outcomes for couples undergoing assisted reproductive techniques.

4.2 PGT in IVF Success Rates ​

Preimplantation genetic testing (PGT) is a sophisticated reproductive technology employed during in vitro fertilization (IVF) to enhance the selection of embryos for transfer. This process enables prospective parents to identify embryos that are free from specific genetic conditions or chromosomal abnormalities, thereby potentially increasing the success rates of IVF treatments.

The methodology of PGT involves several critical steps. Initially, embryos are created through IVF or intracytoplasmic sperm injection (ICSI). Following fertilization, a biopsy is performed on the early embryos at various developmental stages—typically at the cleavage stage or the blastocyst stage—to obtain genetic material for analysis. The sampling can be done from polar bodies or directly from the embryo cells. The genetic material is then subjected to testing for aneuploidies (abnormal numbers of chromosomes) or specific genetic disorders, depending on the type of PGT being performed (PGT-A for aneuploidy, PGT-M for monogenic disorders, or PGT-SR for structural rearrangements) [12][14].

The effectiveness of PGT in improving IVF success rates has been a subject of considerable investigation. Studies indicate that PGT can help in selecting euploid embryos, which are more likely to implant successfully and lead to clinical pregnancies and live births. For instance, a review highlighted that PGT is widely utilized in IVF centers globally to select euploid embryos, thereby improving clinical outcomes in terms of embryo implantation and live birth rates [8]. However, the impact of PGT on overall IVF success rates remains debated, with some evidence suggesting that while PGT may reduce the risk of miscarriage and improve the likelihood of a successful pregnancy, the benefits in terms of cumulative live birth rates (cLBR) compared to IVF without PGT are not definitively established [15].

Furthermore, the application of PGT has been associated with ethical considerations and sociolegal implications, particularly concerning its use for non-medical sex selection and the implications of "designer babies" [16][17]. The growing complexity of genetic testing and the potential for unforeseen outcomes, such as embryo mosaicism, necessitate ongoing research and careful ethical scrutiny [2].

In conclusion, PGT serves as a vital tool in the context of assisted reproductive technologies, aiming to improve IVF success rates by allowing for the selection of genetically healthy embryos. Despite its advantages, the clinical implications of PGT continue to evolve, necessitating a nuanced understanding of its capabilities and limitations in reproductive medicine.

5 Ethical Considerations ​

5.1 Ethical Implications of Genetic Selection ​

Preimplantation genetic testing (PGT) is a sophisticated methodology that involves the assessment of the genetic composition of embryos created through in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI). This process typically includes taking a biopsy of an early embryo, after which genetic testing is performed to select the most viable embryos for transfer to the uterus. PGT has evolved significantly since its inception in the 1990s and is now a fundamental component of assisted human reproduction (AHR) aimed at reducing the risk of transmitting inherited diseases, minimizing implantation failure, and decreasing the likelihood of pregnancy loss [1].

The technological advancements in PGT have allowed for a more comprehensive analysis of embryos, utilizing techniques such as microarray technology and whole genome sequencing. These methods enhance the amount of genetic information obtained, which can aid in embryo selection but also raises complex ethical considerations. For instance, while the ability to select embryos based on genetic characteristics can be seen as an exercise of reproductive liberty, it also leads to socioethical debates regarding the implications of such choices, including the potential for non-medical sex selection and the responsibility of clinicians toward the welfare of future children [17].

The ethical implications of genetic selection through PGT are multifaceted. One major concern revolves around the status of the embryo and the rights of parents versus the rights of the potential child. The increasing detail of information from genetic tests complicates the decision-making process for prospective parents and introduces challenges to reproductive autonomy. Furthermore, the possibility of selecting for traits beyond medical necessity raises questions about societal values and the definition of a "desirable" embryo [18].

Additionally, the ethical discourse encompasses considerations of access to PGT technologies, the potential for exacerbating social inequalities, and the moral ramifications of selecting against certain genotypes. The ethical principles of informed choice, beneficence to children, and social justice are crucial in navigating the integration of PGT into common medical practice [19].

As PGT continues to develop, it is essential for stakeholders, including clinicians, ethicists, and policymakers, to engage in ongoing discussions about the implications of genetic selection. This includes a thorough examination of the ethical paradigms surrounding assisted reproduction, ensuring that advancements in technology align with ethical standards that protect the interests of all parties involved, particularly the future children whose lives are being shaped by these decisions [11].

In conclusion, while preimplantation genetic testing offers significant potential for improving reproductive outcomes, it is accompanied by profound ethical considerations that must be carefully navigated to ensure responsible use of this technology. The evolving landscape of PGT necessitates a balance between technological capabilities and ethical responsibilities, ensuring that reproductive choices are made with careful consideration of their broader implications.

5.2 Psychological Impact on Parents and Society ​

Preimplantation Genetic Testing (PGT) is a sophisticated procedure utilized in conjunction with assisted reproductive technologies such as in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI). The fundamental mechanism of PGT involves the biopsy of early embryos to detect genetic abnormalities. This allows for the selection of embryos that are free from specific genetic conditions or chromosomal abnormalities prior to implantation, thereby reducing the risks associated with unsuccessful reproductive cycles, complicated pregnancies, and genetic diseases in offspring [2].

As the field of PGT evolves, it becomes essential to address the ethical considerations and psychological impacts that accompany its application. The integration of advanced technologies in genetics and embryology raises significant ethical dilemmas, particularly regarding the safety of procedures, clinical validity, and the broader implications for families and society. For instance, the ability to select embryos based on genetic information prompts questions about the moral status of embryos, informed consent, and the potential for discrimination based on genetic traits [1].

From a psychological perspective, the implications for parents undergoing PGT can be profound. The knowledge that they can select embryos based on genetic characteristics may lead to increased anxiety or pressure regarding the decision-making process. Parents may experience emotional distress related to the outcomes of genetic testing, especially if they face the prospect of selecting embryos that may still carry risks for certain conditions, such as mosaicism or variants of unknown significance [2]. The burden of these decisions may also extend to societal levels, where discussions about the ethical use of PGT and the implications of genetic selection could foster a societal divide over reproductive choices [17].

Furthermore, the psychological impact is compounded by the societal implications of PGT. As the technology becomes more widely accepted, there is a potential for shifting societal norms regarding reproduction and disability. The possibility of "designer babies" and the selection of non-medical traits raises concerns about equity and access to reproductive technologies, potentially leading to new forms of social inequality [20]. The ethical principles of beneficence, justice, and respect for autonomy must be carefully navigated to ensure that PGT is applied in a manner that promotes the welfare of future children and respects the diverse values of families and communities [19].

In conclusion, while PGT presents a promising advancement in reproductive medicine, it necessitates a careful consideration of ethical implications and psychological impacts on parents and society. Continuous dialogue among clinicians, ethicists, and the public is essential to navigate the complexities introduced by this technology, ensuring that its applications align with ethical standards and societal values.

6 Future Directions in PGT ​

6.1 Technological Advancements ​

Preimplantation genetic testing (PGT) is a sophisticated procedure employed in reproductive medicine, primarily to identify genetic abnormalities in embryos produced through assisted reproductive technologies such as in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI). The fundamental aim of PGT is to ensure that only embryos free from specific genetic conditions or chromosomal abnormalities are selected for transfer, thereby enhancing the chances of successful pregnancies and reducing the risk of inherited diseases in offspring.

The process of PGT typically involves several critical steps. Initially, embryos are created through IVF or ICSI, after which a biopsy is performed to extract a small number of cells from the developing embryo. This biopsy can be conducted at various stages of embryonic development, such as the cleavage stage or the blastocyst stage, with the latter being preferred due to improved diagnostic accuracy[12]. Following biopsy, genetic testing is performed on the extracted cells to screen for specific genetic abnormalities, including aneuploidies (chromosomal imbalances) and monogenic disorders[2].

In recent years, advancements in technology have significantly enhanced the capabilities and efficiency of PGT. The introduction of next-generation sequencing (NGS) has revolutionized the field, allowing for high-throughput analysis of genetic material and increasing the accuracy of diagnoses[2][12]. This technological progress has not only improved the detection rates of genetic abnormalities but has also expanded the range of conditions that can be screened[4].

Future directions in PGT are likely to be influenced by ongoing technological innovations and the need for standardization in testing protocols. Emerging techniques, such as whole genome sequencing (WGS) and genome editing, hold promise for further improvements in diagnostic capabilities[4]. However, these advancements also introduce complex ethical, privacy, and consent challenges that necessitate careful consideration and public engagement[4]. As PGT continues to evolve, it is anticipated that the integration of more sophisticated bioinformatics tools will enhance the interpretation of genetic data, especially concerning complex findings such as mosaicism and variants of unknown significance[2].

Moreover, there is a growing recognition of the need for standardized protocols to ensure the clinical validity and utility of PGT, alongside the ethical implications associated with its expanding applications[2]. As the field progresses, the goal remains to provide safe, effective, and ethically sound reproductive options for patients, making PGT an integral component of modern reproductive care[1][4].

6.2 Expanding Access to PGT ​

Preimplantation genetic testing (PGT) is a sophisticated procedure that involves the genetic assessment of embryos created through assisted reproductive technologies, such as in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI). The primary goal of PGT is to identify genetic abnormalities or chromosomal conditions in embryos before they are transferred to the uterus, thereby enhancing the chances of a successful pregnancy and reducing the risk of genetic disorders in offspring.

The process of PGT typically begins with the creation of embryos via IVF or ICSI. Once embryos develop to a suitable stage, usually the blastocyst stage, a small biopsy is performed to obtain a few cells from the embryo. This biopsy can be conducted at different developmental stages, including polar bodies, cleavage embryos, or blastocysts, with the blastocyst stage generally providing more reliable results due to the increased number of cells available for analysis[1].

After the biopsy, genetic testing is performed on the extracted cells. This testing can utilize various techniques, including next-generation sequencing (NGS), which allows for comprehensive analysis of the embryo's genetic material. The advancements in technology, particularly in NGS and bioinformatics, have significantly improved the accuracy and efficiency of PGT[2]. The results from these tests inform clinicians and prospective parents about the genetic status of the embryos, enabling the selection of those that are euploid (having the correct number of chromosomes) and free from specific genetic conditions for transfer[12].

Looking toward the future, PGT is poised for further evolution. The integration of emerging technologies such as whole genome sequencing (WGS) and advancements in polygenic risk scoring could expand the applications of PGT beyond traditional uses. This includes the potential for testing for complex polygenic diseases, which have previously been challenging due to the multifactorial nature of their genetic contributions[13]. Furthermore, there is a growing emphasis on addressing the ethical, legal, and societal implications associated with the expanded capabilities of PGT, including issues related to privacy, consent, and the implications of selecting embryos based on a broader range of genetic traits[4].

Expanding access to PGT is another critical focus area. Currently, PGT is not universally available and can be prohibitively expensive for many couples seeking assisted reproductive technologies. Efforts to reduce costs, enhance the efficiency of testing procedures, and increase public awareness about PGT are essential for making this technology more accessible[12]. The continued refinement of biopsy techniques and the development of non-invasive approaches to genetic testing could also play a significant role in broadening access and minimizing the risks associated with embryo biopsy[21].

In summary, PGT operates through a meticulous process of embryo biopsy and genetic analysis to enhance reproductive outcomes. As the field progresses, advancements in technology and ethical considerations will shape the future landscape of PGT, aiming to improve accessibility and broaden its applications in reproductive medicine.

7 Conclusion ​

Preimplantation Genetic Testing (PGT) represents a significant advancement in reproductive medicine, providing prospective parents with the ability to select genetically healthy embryos, thereby improving the chances of successful pregnancies and reducing the incidence of genetic disorders. The primary findings of this report highlight the evolution of PGT from an experimental procedure to a standard practice in assisted reproductive technologies, emphasizing its three main types: PGT for aneuploidy (PGT-A), PGT for monogenic conditions (PGT-M), and PGT for structural rearrangements (PGT-SR). Each type serves distinct purposes in enhancing reproductive outcomes, with PGT-A focusing on chromosomal abnormalities, PGT-M on single-gene disorders, and PGT-SR on chromosomal structural issues. The methodologies employed in PGT, particularly the integration of advanced genetic testing techniques such as Next Generation Sequencing (NGS) and Polymerase Chain Reaction (PCR), have significantly improved diagnostic accuracy and efficiency. However, ethical considerations surrounding genetic selection, including concerns about embryo status, informed consent, and the potential for societal inequality, remain critical issues that necessitate ongoing discourse among clinicians, ethicists, and policymakers. Looking ahead, the future of PGT is likely to be shaped by continued technological advancements, the need for standardized protocols, and efforts to expand access to these essential reproductive technologies, ensuring that PGT remains a safe, effective, and ethically sound option for families seeking to mitigate genetic risks.

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