Duration of storage of cyropreserved human embryos

Abstract

The incidence of cell injury, embryo survival, and implantation following cryopreservation of zygotes and two- to five-cell embryos was studied in 100 patients in order to evaluate the effect of duration of storage. The incidence of individual cell survival was 58% regardless of the length of time kept in liquid nitrogen or the stage of the embryo at freezing. There were 104 of 208 (50%) thawed embryos that survived completely intact, and of those, 24 implanted successfully. Twenty-one (21%) patients had a clinical pregnancy; two of them miscarried Neither the survival of zygotes or cleaved embryos upon thawing nor the incidence of implantation was affected by the duration of cryostorage.

Does storage time influence postthaw survival and pregnancy outcome? An analysis of 11,768 cryopreserved human embryos

“…It is difficult to evaluate the significance of this potential effect because limited clinical outcomes were provided. In contrast, Cohen et al (9) found no significant influence of storage time on blastomere survival or clinical pregnancy, but they did not provide live birth data. These investigators found no difference in blastomere survival or pregnancy outcome in cryopreserved embryos stored from 8 to 70 weeks.…”

“…However, pregnancy outcomes in that study may have been confounded because the transfers occurred during natural and clomiphene citrate cycles. In both reports, embryos were frozen for a relatively short period (8,9).…”

“…Testart et al (8) found increased rates of human embryonic cell death with cryostorage of only several months. In contrast, Cohen et al (9) demonstrated no deleterious effects from cryostorage. Surprisingly, few clinical data are available to address this clinically relevant question.…”

Effects of duration of cryo-storage of mouse oocytes on cryo-survival, fertilization and embryonic development following vitrification

“…Therefore, it appears that the duration of cryo-storage will not affect the outcome of frozen embryos. Several studies carried out in humans indicated that long-term cryo-storage did not affect embryo cryo-survival and pregnancy outcome in the IVF or embryo donation program [31,32]. However, a previous study reported that increased rates in embryonic cell death were found associated with cryo-storage of indicates that the embryos developed to 8-cell stage in the group of cryo-storage for 90-92 days was significantly reduced compared with the group of cryostorage for 8-10 days and the control group, which were similar indicated by a .…”

Live birth from a frozen–thawed pronuclear stage embryo almost 20 years after its cryopreservation

“…An early report by Testart et al (5) found an increase in the rate of embryonic cell death after only a few months of cryostorage. However, Cohen et al (6) showed that the increased length of cryostorage does not have an effect on embryo development and potential. Our center recently reported on a large number of frozen-thawed embryos (more than 11,000) and concluded that the length of storage did not effect survival, implantation, miscarriage, or live birth rates with pronuclear and cleavage stage frozen embryos (4).…”