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Updated: Jul 7, 2026
Cryopreservation of Preimplantation Embryos of Cattle, Sheep, and Goats
Published on: August 5, 2011
Can cumulative pregnancy rates be increased by freezing and thawing single embryos?
Marie Prades1, Jean-Louis Golmard, Danièle Vauthier
1Reproductive Biology Unit, University Hospital, Hôpital Pitié-Salpêtrière, Paris, France. marie.prades@psl.aphp.fr
Objective:
To evaluate the extent to which transfers of frozen single embryos increase cumulative pregnancy rates.
Design:
Retrospective analysis.
Setting:
IVF unit of a university hospital.
Patient(S):
Patients undergoing IVF cycles that were carried out from 2001 to 2005 (n = 1758). Patients were assigned to three groups according to the number of embryos frozen: group A, no cryopreservation; group B, a single embryo frozen; group C, several embryos frozen.
Intervention(S):
Analysis of fresh ETs as a function of the number of embryos frozen and comparison outcomes for the thawing of a single embryo between subgroups B* (only one embryo frozen and thawed) and C* (last embryo of the cohort thawed).
Main Outcome Measure(S):
Implantation and pregnancy rates after fresh ETs and embryo survival and pregnancy rates after the transfer of a single thawed embryo.
Result(S):
The pregnancy rate per fresh ET increased significantly with the number of embryos frozen: 16.2% in group A, 21.4% in group B, and 26.5% in group C. For single thawed embryos, survival was higher in group C* (91.7%) than in group B* (72.6%). The pregnancy rate was also significantly higher in group C* (19.4% vs. 0%).
Conclusion(S):
The freezing of single embryos is of no benefit in cumulative pregnancy rates. ET strategies should therefore be reviewed.
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