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

Objective To evaluate the impact of cryopreservation storage duration on embryo survival, implantation competence, and pregnancy outcome. Design Retrospective study. Setting Academic tertiary-referral infertility center. Patient(s) In vitro fertilization patients and recipients of oocyte donation cycles who had cryopreserved embryos and underwent at least one thaw cycle from 1986 to 2007. Intervention(s) None. Main Outcome Measure(s) Postthaw survival proportion and implantation, clinical pregnancy, miscarriage, and live birth rates. Result(s) Length of storage time did not have a significant effect on postthaw survival for IVF or oocyte donation cycles, or for embryos frozen at the pronuclear or cleavage stages. There was no significant impact of the duration of storage on clinical pregnancy, miscarriage, implantation, or live birth rate, whether from IVF or oocyte donation cycles. Logistic regression analysis demonstrated that the length of storage time or developmental stage at freezing were not predictive of embryo survival or pregnancy outcome. Only oocyte age, survival proportion, and number of transferred embryos were positive predictors of pregnancy outcome. Conclusion(s) Cryostorage duration did not adversely affect postthaw survival or pregnancy outcome in IVF or oocyte donation patients.