Non-invasive Preimplantation Genetic Testing (PGT): further research required

“Non-invasive chromosome analysis of embryos is, as yet, a questionable procedure.” Internationally-recognised IVF clinic, Institut Marquès in Barcelona, looks at why more work is needed on the latest non-invasive method to test the genetic content of embryos.

“At Institut Marquès, we want our patients to take a healthy baby home. In-Vitro-Fertilisation (IVF) treatment along with Preimplantation Genetic Testing (PGT) is the method that permits us to obtain a pregnancy in the shortest period of time, offering the best results. Thanks to PGT we can analyse the genetic content of the embryos in order to distinguish the chromosomally normal ones from those with chromosomal anomalies.

To carry out this test, embryonic DNA is needed. By means of a biopsy we can extract one or a few cells from the embryos for analysis. A few authors have concluded that a biopsy can be too invasive for these analysed embryos to succeed, however if expert embryologists are in charge of performing the biopsy, there is no difference in the implantation potential and the development of the embryos.

Recently, it has been found that the medium in which the embryos are cultured contains, among other substances, DNA that could have emerged from the embryo itself. Therefore, the chance of performing PGT by analysing this free DNA in the culture medium is now being considered. This new method has been named non-invasive PGT. The results so far show that further study is, as yet, required because of the low reliability and precision of the results and the little-known origin of this free DNA in the culture medium.

So far, it appears that non-invasive PGT leads to countless false positives, potentially resulting in embryos being tagged as abnormal when they are, in reality, suitable. This discrepancy between the outcome of the analysis of free DNA in the culture medium and the chromosomal content may be explained by the origin of the free DNA in the culture medium. Some researchers hypothesise that the free DNA comes from lysed (broken) cells or apoptotic cells (cells that have gone through programmed cell death), in which case the DNA analysed would not be representative of the chromosomal content of the cells of the embryo.

Without doubt, carrying out a genetic test on embryos in the safest and easiest posible way, is the future of reproductive medicine. However, whilst the origin of the embryonic DNA in the culture medium is still unknown and results questionable, caution is advised in the use of this new procedure known as non-invasive PGT.”