Effects of the Blastomere Biopsy of Day 3 Human Embryos on Blastocyst Percentage, Cell Number of Obtained Blastocyst and Implantation Rate

Preimplantation genetic diagnosis (PGD) was initially developed to prevent monogenic diseases. However, its use has been extended to improve pregnancy rates in assisted reproductive techniques (ART). These new indications has been called screening for aneuploidy (PGS, preimplantation genetic screening). The current indications for PGS include advanced maternal age, recurrent miscarriage, repeated implantation failure, severe male factor infertility, previous aneuploid pregnancy, poor embryo quality, chemotherapy and radiotherapy and elective single embryo transfer to avoid multiple pregnancies. Nevertheless, the results obtained in the last decade have failed to clearly demonstrate any benefit of PGS in these indications and there are no studies evaluating the effect that biopsy could produce on embryos.

Markers of embryo quality are still very limited and are based on subjective morphological parameters (such as cell number, size and degree of fragmentation) or on the study of embryonic development by measuring the percentage of embryos reaching the blastocyst stage after 120 hours of in vitro culture. Counting the cell number of blastocysts involves the staining and subsequent nuclei counting, which is incompatible with later embryo transfer. A valid alternative to avoid nuclear staining would be a morphometric study using optical sections of different focal planes of the blastocyst and three dimensional (3D) virtual reconstructions.