Embryo evaluation by analysing blastomere nuclei.

Background: To create a more effective selection standard for early embryos, we developed a new grading system consisting of conventional morphological evaluation in combination with analysis of blastomere nuclei.

Methods: A total of 744 embryos used during 459 cycles of embryo transfer on day 2 and blastocyst transfer were subjected to retrospective analysis. The overall implantation rate was 15.