Impact of fresh-cycle variables on the implantation potential of cryopreserved-thawed human embryos

Abstract

Objective: To compare the clinical outcomes of cryopreservation according to the indications for freezing and the outcomes of the fresh cycle from which the embryos were derived.

Design: Retrospective study.

Setting: Private assisted-reproduction unit.

Patient(s): Three thousand, three hundred and sixty-eight embryos in 702 frozen-thawed embryo transfer (ET) cycles.

Intervention(s): Clinical outcomes of frozen-thawed ET cycles in which embryos were derived from fresh conception cycles (n = 436), from fresh nonconception cycles (n = 180), or where the fresh cycle was cancelled due to impending ovarian hyperstimulation syndrome (OHSS) (n = 86).

Main outcome measure(s): Cryosurvival, clinical pregnancy, and implantation rates.

Result(s): Despite similar cryosurvival rates and the transfer of a similar number of embryos, significantly higher clinical pregnancy and implantation rates were obtained in the fresh-conception and OHSS groups. The implantation potential of frozen-thawed embryos that were not selected in a prior fresh cycle was comparable to that of embryos selected for fresh transfer.

Conclusion(s): The success of frozen-thawed ET depends on the outcome of fresh ET and the indications for cryopreservation. Success is similar to that of fresh ET cycles in patients who had all their embryos frozen due to impending OHSS.