Embryo biopsy

Embryo biopsy can be detrimental to at least some embryos. The feasibility of embryo biopsy must be discussed not only with the physician, but also with an embryologist when possible. The experience of the individual performing the biopsy is very important. 

At the time of the biopsy, a human embryo is at the blastocyst stage. It has a so-called inner cell mass (from which a fetus will develop) and trophectoderm (future placenta). The number of cells at this stage varies from about 100 to 500.  

During the biopsy, a sample of cells from the trophectoderm is removed for analysis.

A grey clump of cells (on the left) is an embryo biopsy sample. Insert on the right is the same clump counterstained with DAPI to visulaize nuclei. Each blue spot corresponds to a nucleus. In this case there are about 12 cells in the sample.

A biopsy may reduce embryo viability

There are two assumptions made in recommending embryo biopsy to every patient:

  • In vitro culture to the blastocyst stage (5-6 days) does not adversely affect embryo viability
  • Embryo biopsy does not adversely affect embryo viability

Both of these assumptions in my opinion are questionable. From my personal experience, I strongly believe that culture to the blastocyst stage can be detrimental for some otherwise viable embryos. Furthermore, some embryos would have a better chance of development if transferred into the uterus immediately after fertilization, without any in vitro culture. As to the impact of the biopsy on the embryos, this recent anonymous survey of embryologists suggests that many of them are concerned: 

Additionally, there are no mandated standards of training or certification required to perform the biopsy. Therefore biopsy techniques vary greatly from laboratory to laboratory and from operator to operator as well as the benchmarks of embryo eligibility for a biopsy. This means that some laboratories will biopsy even low-quality embryos that may not survive the biopsy. “Survival” in this context does not mean that the embryo is destroyed by the biopsy, but rather its viability is reduced to the point that it is unlikely to continue development. 

Furthermore, I believe this explains why we do not see expected improvements in pregnancy rates with PGT. 

Not all blastocysts qualify for a biopsy

Making a decision on whether an embryo can safely be biopsied requires careful consideration and experience. For example, both blastocysts below are probably perfectly fine embryos. However, biopsying the one on the left will likely render it non-viable, because it does not have many cells in the trophectoderm.  

Summary

Embryo biopsy is not harmless. It may reduce embryo viability. Deciding whether the embryo is good a candidate for a biopsy requires considerable experience.    

Minimal Impact Biopsy

We developed and use, what we call “Minimal Impact biopsy”. This does not eliminate every concern but makes the biopsy safer for an embryo.  

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