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269
ISSN:3030-3621
THE EFFICACY OF PREIMPLANTATION GENETIC TESTING FOR
ANEUPLOIDY (PGT-A) IN IMPROVING CLINICAL PREGNANCY RATES
Pakhomova Janna Evgenevna,
Bakhodirova Shahnoza Fayzullaevna
Abstract.
Preimplantation genetic testing for aneuploidy (PGT-A) has become
an integral part of assisted reproductive technologies (ART) aimed at improving
clinical pregnancy rates by selecting genetically viable embryos for transfer. Among
the most common methods of PGT-A are fluorescence in situ hybridization (FISH) and
next-generation sequencing (NGS), each with distinct advantages and limitations. This
thesis investigates and compares the clinical outcomes of these methods, particularly
focusing on clinical pregnancy rates and the proportion of euploid embryos, in women
of varying reproductive age. Recent studies have shown that while both methods serve
to increase clinical pregnancy rates, NGS/SNP has demonstrated superior efficacy in
identifying a wider array of chromosomal abnormalities, leading to better outcomes,
particularly for women of advanced maternal age. The ability of NGS/SNP to detect a
broader spectrum of chromosomal issues, including microdeletions and translocations,
makes it more accurate in selecting genetically healthy embryos for transfer. In
contrast, FISH, despite its advantages in detecting certain chromosomal abnormalities,
has a narrower range of detection, often missing more complex aneuploidies, especially
in older women. In clinical studies, NGS/SNP has been shown to result in higher
clinical pregnancy rates compared to FISH. For instance, a study by Munné et al.
(2018) demonstrated that NGS/SNP improved clinical outcomes significantly for
women over 35 years, achieving a pregnancy rate of 66.67% compared to 40% with
FISH (Munné et al., 2018). Furthermore, NGS/SNP's higher sensitivity enables more
accurate identification of euploid embryos, which is crucial for improving pregnancy
success rates. Although NGS/SNP is more expensive and requires a longer processing
time compared to FISH, its ability to detect a broader range of chromosomal
abnormalities offers a more reliable and comprehensive approach to embryo selection.
As a result, NGS/SNP is increasingly becoming the method of choice in ART,
particularly for women with advanced maternal age who face a higher risk of
chromosomal abnormalities and miscarriage.
FISH in Preimplantation Genetic Testing. FISH was one of the earliest methods
used in PGT-A, particularly for screening common aneuploidies such as trisomies 13,
18, and 21. However, studies have shown that FISH’s limited ability to detect a broad
range of chromosomal abnormalities makes it less effective for women over 35, who
are at an increased risk for a variety of chromosomal defects. A study by Fragouli et
Ta'lim innovatsiyasi va integratsiyasi
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ISSN:3030-3621
al. (2017) highlighted that FISH, while useful in certain contexts, does not account for
more complex genetic anomalies, such as translocations or microdeletions, which can
be critical for embryo selection (Fragouli et al., 2017).
NGS/SNP in Preimplantation Genetic Testing. NGS/SNP provides a more
comprehensive analysis, enabling the detection of a wider range of chromosomal
abnormalities, including those not covered by FISH. This method has shown to
improve clinical pregnancy rates, particularly in women of advanced maternal age. In
a study by Rechitsky et al. (2021), women over 35 who underwent PGT-A with
NGS/SNP achieved a pregnancy rate of 66.67%, significantly higher than the 18.18%
pregnancy rate observed in those who did not undergo genetic testing (Rechitsky et al.,
2021). NGS/SNP's sensitivity allows for more precise embryo selection, reducing the
likelihood of miscarriage and increasing the chances of a successful pregnancy.
Clinical Efficacy of NGS/SNP. The efficacy of NGS/SNP has been consistently
demonstrated across multiple studies, showing its superior performance in improving
clinical pregnancy rates compared to FISH. In a comprehensive review by McCulloch
et al. (2020), NGS was found to outperform FISH in both embryo quality assessment
and clinical pregnancy outcomes, particularly for women with a higher risk of
chromosomal abnormalities (McCulloch et al., 2020). Additionally, the ability of NGS
to screen all 24 chromosomes, rather than just a select few, gives it a significant
advantage in ensuring the transfer of healthy embryos.
Cost and Time Considerations. One of the primary drawbacks of NGS/SNP is
its cost and the longer time required for genetic analysis. However, given the higher
clinical pregnancy rates and reduced miscarriage rates associated with NGS/SNP, the
method's cost-effectiveness is increasingly being recognized, especially in women of
advanced maternal age, for whom the risk of chromosomal abnormalities is
substantially higher (Harper et al., 2020).
Conclusion.
This review emphasizes the growing role of NGS/SNP in ART,
particularly for older women, and underscores the need for further research to optimize
PGT-A protocols. NGS/SNP's ability to offer a more accurate genetic screening profile
makes it a valuable tool in improving clinical outcomes, reducing miscarriage rates,
and ensuring the birth of genetically healthy children. Despite its higher cost and longer
analysis time, NGS/SNP offers a clear advantage over FISH, especially for women
with a higher risk of chromosomal abnormalities, and is expected to become the gold
standard in PGT-A.
References:
1.
Munné S, Magli C, Grifo J, et al. Comprehensive chromosome screening improves
ART
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ISSN:3030-3621
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