Pronuclear morphology, embryo development and chromosome constitution

The aim of the present study was to evaluate the usefulness of pronuclear patterns, according to the classifications of Tesarik and Scott, as predictors of embryo chromosome constitution. Up to 73 preimplantation genetic diagnosis/preimplantation genetic screening (PGD/PGS) cycles were analysed in this retrospective study including 17 cycles of translocation carriers and 56 PGS cycles. A total of 331 biopsied embryos were studied assessing pronuclear (PN) pattern, embryo quality and chromosome constitution. As regards to the relationship between PN pattern and embryo quality, the data obtained in this study show no correlation between both parameters. Although there were no significant differences when comparing the distribution of chromosomally normal and abnormal embryos with respect to embryo quality, such differences were observed when distinguishing between normal, aneuploid and polyploid embryos. The results show that the PN pattern using Tesarik’s and Scott’s classification systems is not related to the embryo developmental potential or its chromosome constitution. Therefore, in the context of a PGD/PGS programme, the PN pattern cannot be used as a tool to predict embryo quality or chromosome status.