Advancements in Preimplantation Genetic Diagnosis: Enhancing Fertility and Pregnancy Outcomes

Preimplantation Genetic Diagnosis

Aneuploidy is the leading cause of implantation flures and pregnancy losses in older women. Preimplantation genetic testing PGT is a crucial tool to address age-related declines in fertility by screening embryos prior to pregnancy for chromosomal abnormalities during in vitro fertilization IVF. PGT acts as an umbrella term encompassing preembryonic examination before implantation or conception, offering a safer and more effective alternative compared to current prenatal diagnosis methods.

Currently recognized types of PGT include:

1. PGTa: Embryos are screened for aneuploidy through various techniques.

2. PGTm: This is specifically utilized when genetic abnormalities in one or both parents are identified, with testing on the embryo to ascertn if it carries these same anomalies.

3. PGTsr: screening embryos for specific chromosomal rearrangements like balanced translocations.

PGT offers a unique advantage by ensuring that only healthy embryos are implanted, thus reducing miscarriages and pregnancy complications such as multiple births, preterm deliveries, or low birthweight infants when single embryo transfer is performed. As advancements in IVF techniques have progressed, focusing on blastocyst culture, biopsy of trophectoderm cells, aneuploidy screening with NGS or CGH methods, and the introduction of newer sequencing platforms like next-generation sequencing NGS have significantly enhanced safety and accessibility for patients undergoing IVF.

The modern IVF protocol involves culturing embryos until blastocyst stage followed by biopsy, PGT to screen for aneuploidy, and a single embryo transfer, thereby minimizing risks.

History

In 1968, Edwards and Gardner pioneered rabbit embryo biopsies. In trials in the UK during the mid-1980s, preimplantation genetic testing evolved as a noninvasive prenatal alternative to invasive techniques like amniocentesis or chorionic villus sampling. In 1989, Handyside and colleagues successfully reported the birth of an unaffected child following PGT med at avoiding X-linked disorders.

Recent Developments

PGT-A has witnessed significant growth in recent years, comprising around 40 of IVF cycles in the US. The technique's evolution involved improvements in embryo culture techniques, blastocyst biopsy methods, and aneuploidy screening platforms such as NGS and CGH analysis. PGT-M is now avlable for most known genetic mutations.

Key Points

• Preventing Risks: By eliminating embryos with chromosomal anomalies before implantation, PGT avoids the need for postconception diagnostics that may require pregnancy termination.

• Enhanced Outcomes: Single embryo transfer facilitated by PGT leads to improved implantation rates and reduced miscarriage risks compared to multiple gestations.

• Technological Advancements: Modern IVF protocols prioritize blastocyst culture, biopsy of trophectoderm cells, aneuploidy screening methods NGS, CGH, and single embryo transfer.

PGT is a transformative tool in reproductive medicine offering hope for the prevention of heritable genetic diseases through early detection of chromosomal abnormalities. Its continuous evolution ensures safer, more precise, and patient-focused outcomes as part of modern IVF procedures.

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