EVALUATION OF CYTOGENETIC ANALYSIS FOR CLINICAL PREIMPLANTATION DIAGNOSIS

Objective: To evaluate the feasibility of using cytogenetic analysis i n preimplantation diagnosis. Design: Two different biopsy protocols (c hemical drilling and zona cutting) and two fixation methods were teste d in a mouse model. Afterwards, the efficiency of obtaining chromosome preparations from untransferable human embryos depending on the metho d used to obtain the blastomeres (embryos biopsy or removal of the zon a pellucida and blastomere disaggregation) was determined. The chances of obtaining chromosome preparations depending on the type of embryo (haploid, diploid, triploid, and apparently unfertilized) were also ev aluated. Results: Results from the mouse model showed that chemical dr illing yields better results than cutting in terms of metaphases per b iopsied embryo and surviving rate after biopsy. In human embryos, biop sy of diploid embryos produced 46.6% chromosome preparations, while 29 % were obtained after blastomere disaggregation and 20.4% when biopsyi ng triploid embryos. Conclusions: These results suggest that the disag gregating procedure and triploid embryos cannot be considered as good models to assess the feasibility of cytogenetic analysis in preimplant ation diagnosis. Poor chromosome quality and loss during fixation are the main problems to use cytogenetics in preimplantation diagnosis; a combination of cytogenetics and other techniques is suggested in cases of balanced translocations.