Researchers at the Research Institute of Medical Genetics of the Tomsk National Research Medical Center have found that chromosomal abnormalities contribute more to spontaneous miscarriage than previously believed. The study suggests that almost 68% of embryos carry chromosomal mutations incompatible with development, rather than the commonly cited 50%. These findings were reported to socialbites.ca by the Ministry of Education and Science of the Russian Federation.
Globally, about 23 million pregnancies end in miscarriage each year. Approximately 10 to 15 percent of pregnant women experience this outcome, with chromosomal abnormalities being the primary cause of developmental failure in embryos.
Researchers employed state-of-the-art technologies, including genome-wide analysis on microarrays with parental chromosome variant assessments. For the first time in international practice, they conducted a comparative study on tissues from different germ layers. This approach revealed mutations in 35% of embryos that appeared normal at the chromosome level, uncovering abnormalities that were previously undetectable, according to Vadim Stepanov, Director of the Tomsk National Research Medical Center and Academician of the Russian Academy of Sciences, as reported to socialbites.ca.
The study enhances the precision of diagnosing chromosomal abnormalities and sheds light on the causes behind most miscarriages. It also reduces the need to search for other potential factors linked to maternal health that may contribute to pregnancy loss.
One notable finding involves chromosomal mosaicism, where one tissue shows a mutation while another does not. This raises questions about reliable results, since analyzing at least two tissue types is necessary. To date, this broader analysis has not been performed, according to Igor Lebedev, Deputy Director of Scientific Work at the Tomsk National Research Medical Center and head of the genetics laboratory there, as reported to socialbites.ca.
The results imply that protocols for preimplantation genetic testing during in vitro fertilization should be updated. Specifically, when an embryo is analyzed during IVF, the protocol should account for mosaicism risks and the limitations of testing the inner cell mass, the tissue that ultimately forms the fetus.
Currently, during IVF procedures, a portion of trophectoderm cells, which contribute to the placenta rather than the embryo itself, is often sampled for genetic analysis. If a chromosomal set is normal, the transfer is straightforward. However, recent years have seen a rise in the use of mosaic embryos, where trophectoderm cells show a mix of normal and abnormal chromosomal content. This mosaicism is associated with an increased risk of miscarriage, emphasizing the need for careful interpretation of test results.
Lebedev notes that the risk stems from the fact that the inner cell mass, which will develop into the fetus, is not directly assessed by standard preimplantation genetic testing. The current study demonstrates for the first time that spontaneous miscarriage correlates with an accumulation of mosaic chromosome abnormalities, especially in cells originating from the inner cell mass. This insight helps clinicians better understand why some pregnancies end early and how to refine testing strategies for IVF candidates.
Earlier commentary from gynecologist Ilyina discussed factors contributing to premature birth, adding context to the broader conversation about embryo development and pregnancy outcomes. The new findings underscore the importance of comprehensive genetic assessment in early stages of assisted reproduction and suggest a shift toward more nuanced diagnostic pathways.