Embryos showing mosaicism in trophoectoderm cells can achieve good pregnancy rates. IB research presented at the ESHRE 2016.

At the European Society of Human Reproduction and Embryology (ESHRE) that will be held this year in Helsinkihan, Dr. Ruth Morales will present her work entitled “Mosaic embryos can achieve good IVF success rates”.

Chromosomal mosaicism, which consists of the presence of cell lines with a different chromosome set is a frequent occurrence with embryos derived from in vitro fertilization IVF cycles. For their detection, the embryos must be left in culture until day 5 or 6, at which point an embryo biopsy of the trophectoderm is carried out as well as a genetic analysis for all chromosomes using array- CGH methodology. This technique is sensitive enough to detect the majority of mosaic embryos but until recently this phenomenon was never evaluated or taken into account when deciding which embryo would be suitable for transfer.

To determine its importance and what to do on detection, in this work carried out by the Instituto Bernabeu Biotech team, the results of IVF cycles involving the transfer of mosaic embryos were evaluated. In order to carry this out, 1,362 embryo biopsieswere reanalyzed and chromosomal mosaicism was found in 183 embryos (13.4%), in which good rates of implantation and evolutive pregnancies were achieved.

Some authors have suggested that mosaicism can only be confined to the trophectoderm or extraembryonic tissue that will give rise to the placenta and does not affect the inner cell mass that will form the future embryo, or even that there may be some kind of self-correction mechanism in the embryo, thereby not affecting the results of either the cycle or the new-born.  

Based on this data, we can conclude that mosaic embryos derived from IVF cycles should not be discarded since they have implantation potential and are capable of generating an evolutive pregnancy.

Mosaic embryos can achieve good IVF success rates.

R. Morales, B. Lledó, J. Órtiz, H. Blanca, J. Ll. Aparicio, R. Bernabeu.

ESHRE 2016, HELSINKI