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 is 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 order to find a relationship that could show the embryo's potential future development and so increase implantation rates. A total of 66 normally fertilized human embryos were biopsied at the 6- to 10-cell stages. At day 6, blastomeres were counted by nuclear labelling. A total of 33 embryos (50%) reached the blastocyst stage. Of the isolated blastomeres, 63% divided and 53% cavitated over 3 days in culture. Of the blastomeres taken from embryos that developed to the blastocyst stage, 88% divided, 79% cavitated, 76% divided and cavitated and 9% neither divided nor cavitated. In those from arrested embryos, 39% divided (P < 0.001), 21% cavitated (P < 0.001), 15% divided and cavitated (P < 0.001) and 55% neither divided nor cavitated (P < 0.001). Blastomeres biopsied from embryos that reached the blastocyst stage showed 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 and that are probably more suitable to implant. Cryopreserving biopsed embryos and culturing blastomeres would increase implantation rates. Embryos can then be selected according to the blastomere development and thawed for transfer in a future cycle.