New study by Instituto Bernabeu determines which type of embryo biopsy provides a least damage of the embryo and a higher success rate of the cycle


In the last meeting of reproductive medicine experts, the European Fertility Congress (ESHRE), we presented a new research developed entirely at Instituto Bernabeu clinics. The study focused on how the technique used for the biopsy prior to an embryonic genetic study (pulling and flicking) affected the genetic results, the rate and type of embryonic mosaicism, as well as the success of PGT-A cycles.

Embryo biopsy is a routine assisted reproduction technique that consists of taking between 5 and 10 cells from the trophoectoderm of the blastocyst developed in vitro, with the help of micromanipulation equipment and a laser. These biopsied cells are genetically analyzed and thus each embryo is diagnosed as chromosomally normal, chromosomally abnormal or mosaic.

The biopsy can be done in different manners – using the laser to a greater or lesser extent. In the previous studies an excessive use of the laser was associated with an increased percentage of mosaic embryos.

The aim of this study is to assess the influence on the genetic and reproductive outcome of two techniques of embryo biopsy: pulling, associated with greater use of laser and flicking which requires fewer laser pulses per embryo biopsied.

In this study, the biopsy results of 499 embryos were analyzed. We observed that the embryos biopsied using pulling technique indeed required a greater number of laser pulses and showed a higher rate of mosaic embryos.  In addition, these mosaics were simpler (of low grade and involving a lower number of chromosomes) than the mosaics observed when flicking method was implemented.

The results of PGT-A cycles observed upon transferring these mosaic embryos were similar in both groups. However, we must take into account that the number of embryo transfers was very low and that the simpler mosaics showed a higher implantation rate, although the difference was not significant.

Therefore, we concluded that more than four laser pulses can increase the rate of diagnosed mosaicism and that this may be due to the excessive laser use since mosaics are simple and their implantation rate is practically the same as observed for euploid, chromosomally normal, embryos.


Is mosaicism rate and characteristics influenced by the method of trophectoderm-biopsy technique employed in PGT-A cycles? Genetic results and reproductive outcome after pulling versus flicking

Herrero L., Aparicio M., Cascales L., Ortiz JA., Castillo JC. García-Ajofrín C, Ten J., Bernabéu R.

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