The viability of cryopreserved embryos is determined by a combination of biological and technical factors. Regardless of the technicians’ experience level and technical skill, some attrition in the recovery of viable embryos at thaw and the number of embryos that will result in live-born offspring upon transfer should be expected.
One should estimate that 20-25% of frozen-thawed embryos will produce live offspring; therefore, we recommend preserving sufficient embryos to re-establish a given line a few times before an additional cohort of embryos would need to be cryopreserved. In general, this is between 100-300 embryos per rodent model. Zeeva has preserved 250-300 embryos per rodent model.