Harriet HeywoodCambridgeshire
PA Media
The Cambridge study found that pre-implantation genetic testing could mislabel embryos as abnormal when the abnormalities were in the placenta
Researchers have raised concerns about the reliability of a widely used IVF screening method, which checks for chromosomal abnormalities.
Scientists at the Loke Centre for Trophoblast Research, University of Cambridge, said the test, used in many fertility clinics for IVF, was likely to overestimate the number of embryos with abnormalities.
The treatment is often offered to older women or women with a history of miscarriage or failed IVF cycles.
However, scientists believed the test could be picking up errors in cells that would form in the placenta, rather than those that had developed in the embryos.
The test, known as pre-implantation genetic testing for aneuploidy (PGT-A), is designed to screen embryos before implantation.
When abnormalities were detected, the embryo may be deemed inviable and discarded, so patients may undergo another cycle of treatment, which can be costly.
But new research suggested that some of the abnormalities detected by the tests may not be relevant to the embryo’s viability.
Looking to better understand the development of the embryo at its early stage, Cambridge researchers and the Francis Crick Institute developed a new, state-of-the-art method to watch embryos live in high resolution.
It used fluorescent tagging to track cell division in 3D.
Abnormalities arise at a relatively late stage of the embryo’s development and appear in the outer layer of the blastocyst.
The blastocyst develops into the placenta, and it is from this layer that biopsies were taken for pre-genetic testing.
First author Dr Ahmed Abdelbaki, a postdoctoral researcher at the Loke Centre, said it was the first time the imaging technique had been used, and it allowed them to see what was happening.
“It meant that we could watch the embryos as they developed over a two-day period, the longest continuous time that this process has been observed.”
Co-author Professor Ben Steventon from the Department of Genetics at the University of Cambridge said: “It’s proof of the power of direct observation to uncover unexpected findings in human biology.”
The embryos in the study were donated by families who had successful pregnancies.
Professor Kathy Niakan, director of the Loke Centre and chair of Cambridge Reproduction, said her team was now studying cells in the inner cell layer, which forms the fetus.
“Much more basic research is needed to inform future clinical practice and improve rates of assisted conception,” she added.