What We've Learned From Transferring "Abnormal" Embryos

For many years, embryos identified as "abnormal" through preimplantation genetic testing for aneuploidy (PGT-A) were generally considered unsuitable for transfer. Today, a growing body of evidence has challenged that assumption.

When PGT-A became widely adopted around 2014, many patients were devastated to learn that none of their embryos were classified as "normal." 

At the Center for Human Reproduction (CHR), we have long emphasized that PGT-A is a screening test, not a diagnostic test. Research over the past decade has increasingly supported this position, demonstrating that some embryos labeled as abnormal can still lead to healthy pregnancies and the birth of healthy babies. In other words, an "abnormal" PGT-A result does not necessarily mean an embryo has no chance of resulting in a healthy child.

One possible explanation is a phenomenon researchers are continuing to investigate known as embryonic "self-correction." Studies in mouse models suggest that some embryos containing both normal and abnormal cells may continue to develop by selectively favoring the normal cells over time. While more research is needed to fully understand whether and how this process occurs in humans, these findings have prompted a reevaluation of how certain PGT-A results are interpreted.

However, not every embryo with an abnormal PGT-A result is an appropriate candidate for transfer. Some chromosomal abnormalities are not compatible with normal fetal development. The decision to consider transferring an embryo with an abnormal result depends on several factors, including the specific chromosome involved, the type of abnormality identified, the patient's reproductive history, and their personal goals and values.

At the CHR, our role is not to tell patients what decision to make, but to provide them with the most accurate, evidence-based information so they can make informed choices about their care.

To learn more about transferring "abnormal" embryos, listen to the latest episode of The Egg Factor featuring Dr. Norbert Gleicher here.