Impact of blastomere biopsy and cryopreservation techniques on human embryo viability

The purpose of the present study was to evaluate the effect of cryopreserva tion on 55 embryos which had one blastomere biopsied for preimplantation ge netic diagnosis of aneuploidy before freezing, The thawing outcome was comp ared to that obtained in 94 embryos which derived from our conventional fre ezing programme in patients with comparable characteristics who were treate d in the same period. Their embryos were morphologically similar but the in cidence of aneuploidy was 100% in the biopsy group and unknown in the contr ols. The percentage of embryos which survived intact after thawing was sign ificantly lower in the biopsied group compared to the controls (9 versus 25 % respectively; P < 0.025), whereas the rate of lysis was superior among bi opsied embryos (34 versus 13% in the controls; P < 0.001). Similarly, the s urvival index was higher in the frozen-intact embryos than in the embryos w hich were frozen after biopsy (61 versus 38%; P < 0.001). No empty zonae re sulted in the control group, while six were found after thawing biopsied em bryos. In the second part of the study, blastomere biopsy was implemented o n 102 thawed embryos generated by 16 patients. The chromosomal analyses rev ealed that 49 were normal, leading to the transfer of 2.5 +/- 0.8 embryos p er patient. Only three clinical pregnancies were obtained, and are presentl y ongoing. In conclusion, the present findings discourage the use of conven tional cryopreservation protocols in strategies involving preimplantation g enetic diagnosis in human reproductive medicine. Adequate protocols are req uired for freezing and thawing embryos which have been subjected to biopsy procedures.