‍

In the world of in vitro fertilization (IVF) and preimplantation genetic testing for aneuploidies (PGTA), the term "Mosaicism" has gained significant attention in recent years. As technology advances, our understanding of embryo genetics and its impact on pregnancy outcomes continues to evolve. In this blog post, we'll explore the concept of Mosaicism, its implications for PGTA results, and the current recommendations for managing Mosaic embryos.

What is Mosaicism?

Mosaicism refers to the presence of two or more cell types with different genetic compositions within a single embryo. When an embryo undergoes PGTA, a biopsy of cells is taken and analyzed. A Mosaic PGTA result indicates that some cells in the biopsied sample have the normal number of chromosomes (euploid), while others have an abnormal number (aneuploid). Approximately 10% of PGTA-tested embryos are identified as Mosaic.

The Implications of Mosaic PGTA Results

Prior to the advent of advanced PGTA technology, embryos were classified as either euploid or aneuploid. However, with the ability to detect Mosaicism, a new category of embryos has emerged. When the percentage of abnormal cells is low, it has been shown that transfer of these embryos are safe. Studies have shown that the transfer of true Mosaic embryos is associated with significantly higher rates of pregnancy loss and failed implantation compared to the transfer of euploid embryos. Most doctors are comfortable transferring mosaic embryos where the abnormal diagnosis could not result in a live birth. For example, if the Mosaic involves Down Syndrome, it is probably best not to transfer these embryos since the baby could be born with the abnormality.

While live births resulting from the transfer of Mosaic embryos have been reported, and the offspring appear to be healthy thus far, it is crucial to recognize that long-term developmental and health outcomes are still unknown. It will take years of follow-up to fully understand the implications of transferring Mosaic embryos.

Current Recommendations for Managing Mosaic Embryos

Given the limited data on the outcomes of Mosaic embryo transfers, euploid embryos are always prioritized for transfer over Mosaic embryos. If PGTA results reveal that only Mosaic embryos are available, the preferred approach is to undergo an additional round of IVF and PGTA with the goal of producing euploid embryos.

The decision to transfer Mosaic embryos is generally not recommended until more is known about the long-term development and health of individuals born from these embryos. However, the choice to preserve Mosaic embryos for potential future use is a complex and personal one that should be discussed thoroughly with your medical team.

Conclusion

As our understanding of Mosaicism and its implications for PGTA results continues to grow, it is essential for individuals undergoing IVF to stay informed and work closely with their healthcare providers. While the transfer of Mosaic embryos is not currently recommended as a first-line approach, ongoing research may provide more insights into the potential outcomes and management strategies for these embryos in the future.

For more information on related topics, check out our recent articles on understanding your PGT-A report, the lifespan of frozen embryos, and comparing different types of PGT cycles.

The content on this blog is for informational purposes only and is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always consult with a qualified healthcare provider before making any health-related decisions or implementing any medical information shared here.