Blastomere development after embryo biopsy: a new model to predict embryo development and to select for transfer

One of the most important and unsolved problems in in-vitro fertilization i s to decide which embryos are more suitable to implant and therefore should be transferred. We analysed the in-vitro development of isolated biopsied blastomeres and compared it to the development of the original embryo, in o rder to find a relationship that could show the embryo's potential future d evelopment and so increase implantation rates, A total of 66 normally ferti lized human embryos were biopsied at the 6- to 10-cell stages. At day 6, bl astomeres were counted by nuclear labelling. A total of 33 embryos (50%) re ached the blastocyst stage, Of the isolated blastomeres, 63% divided and 53 % cavitated over 3 days in culture. Of the blastomeres taken from embryos t hat developed to the blastocyst stage, 88% divided, 79% cavitated, 76% divi ded and cavitated and 9% neither divided nor cavitated, In those from arres ted embryos, 39% divided (P < 0.001), 21% cavitated (P < 0.001), 15% divide d and cavitated (P < 0.001) and 55% neither divided nor cavitated (P < 0.00 1). Blastomeres biopsied from embryos that reached the blastocyst stage sho wed a significantly higher proportion of division and cavitation than those originated from arrested embryos. Culture of the isolated blastomeres can demonstrate those embryos more likely to develop to the blastocyst stage an d that are probably more suitable to implant. Cryopreserving biopsed embryo s and culturing blastomeres would increase implantation rates. Embryos can then be selected according to the blastomere development and thawed for tra nsfer in a future cycle.