Pregnancy outcome following fresh vs frozen embryo transfer into gestational carriers using a simplified slow freeze protocol.

To compare pregnancy rates following fresh vs frozen embryo transfer into gestational carriers.Choice of deferring fresh embryo transfer and cryopreserving the embryos vs fresh transfers was not randomized but based on circumstances. The cryopreservation protocol used a simplified slow cool technique avoiding the planar programmable freezer and using a one-step removal of the cryoprotectant.The live delivered pregnancy rate was 51.0% (49/96) for fresh embryo transfer vs 34.3% for transfers of frozen thawed embryos in gestational carriers not having a fresh embryo first.Using the simplified slow cool cryopreservation protocol with a one-step removal of cryoprotectants pregnancy rates are comparable to what is found in women of similar ages undergoing controlled ovarian hyperstimulation followed by IVF-ET. However, when transferring to a gestational carrier the live delivered pregnancy rates are 50% higher with fresh embryo transfer.