Abnormal chromosome number, or aneuploidy, is common in human embryos. It is responsible for more than half of all miscarriages, and it is the leading cause of congenital birth defects. Besides, it has been described that aneuploidy may also affect embryo implantation. Therefore, selecting embryos that have the best chance of implanting and growing into a healthy baby is one of the most important steps in the field of assisted reproduction. Recent advances in genetic technologies, such as Next-Generation Sequencing (NGS), have allowed aneuploidy to be detected with greater sensitivity. The application of this technique to trophectoderm biopsies, taken from embryos before transfer to the uterus, has provided insight into the clinical impact of chromosomal status. This process of screening embryos to make sure they have the right number of chromosomes and to look for any structural abnormalities in the chromosomes is called Preimplantation Genetic Testing for Aneuploidy (PGT-A). It requires specific equipment and trained personnel that will add costs and risks, so non-invasive techniques are sought as an alternative. These non-invasive procedures have been explored by some groups analyzing the spent culture medium where the embryo is cultured up to the time of transfer or freezing. In daily routine, this media is discarded after finishing the embryo culture, but it has been reported that contains traces of embryonic cell-free DNA (cfDNA) that can represent the genetic load of the embryo. However, at the moment there is a high variability in results across studies, with a percentage of concordant results between the media and the trophectoderm biopsy ranging from 3.5 to 85.7%. Thus, the main objective of this project is to validate a new non-invasive method for PGT-A (niPGT-A), based on improved collection and analysis of the culture media to achieve higher rates of sensitivity and specificity and to decrease the effect of some intrinsic difficulties such as low embryonic cfDNA input, mosaicism and maternal contamination.
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Chromosomal status of the embryos
Timeframe: 6 to 7 days of embryo development