Shipping cryopreserved embryos to long term storage: are outcomes affected?

Abstract

OBJECTIVE: Relocating cryopreserved embryos to a long term storage facility is an attractive option for the IVF laboratory. Due to the benefits, including minimizing the liability for abandoned embryos and reducing the need for numerous storage tanks, both Kaiser IVF centers in CA chose to transport embryos to offsite storage. An assessment of this policy was completed. DESIGN: Retrospective comparative study. MATERIALS AND METHODS: The records for FET cycles between Oct.'08 and Mar.'09 were reviewed for survival rate (SR), implantation rate (IR) and clinical pregnancy rate (CPR). Embryos were frozen at the blastocyst stage or the 2PN zygote stage using standard slow freezing techniques in vials or straws. The outcomes of (Group A) FET cycles using embryos that were shipped to a long term storage facility (Reprotech Ltd, Reno, NV) and then shipped back to our facility were compared to the outcomes of (Group B) FET cycles that used embryos that were never shipped. All blastocysts frozen were at least of grade 3BB or better on day 5 or 6. All zygotes were frozen with visible pronuclei. Embryos were transported in dry LN2 shipping vessels by either Reprotech staff or FedEx. A cryo guard vial was used to indicate whether a rise in temperature of the tank occurred during shipment. RESULTS: 13 FET cycles represented Group A. 37 embryos were thawed with a 85.2% SR, IR of 41.9% (13/31) and CPR of 61.5% (8/13). Group B comprised of 62 FET cycles resulted in a 78.2% SR, IR of 25.3 % (37/146) and CPR of 41.3 % (26/63). Clinical pregnancy is defined as the presence of a fetal sac by ultrasound at 6 weeks. CONCLUSIONS: Transferring frozen inventory to a long term storage facility is a successful strategy to minimize burdens associated with in house storage. Our results demonstrate that out sourcing frozen embryo storage does not adversely affect the ability to achieve normal survival, implantation and clinical pregnancy rates. Future studies to include vitrified specimens are needed as vitrification methods become standard practice.