Can cumulative pregnancy rates be increased by freezing and thawing single embryos?
OBJECTIVE
To evaluate the extent to which transfers of frozen single embryos increase cumulative pregnancy rates.


METHODS
Retrospective analysis.


METHODS
IVF unit of a university hospital.


METHODS
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.


METHODS
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).


METHODS
Implantation and pregnancy rates after fresh ETs and embryo survival and pregnancy rates after the transfer of a single thawed embryo.


RESULTS
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%).


CONCLUSIONS
The freezing of single embryos is of no benefit in cumulative pregnancy rates. ET strategies should therefore be reviewed.
Prades
Marie
M
Reproductive Biology Unit, University Hospital, Hôpital Pitié-Salpêtrière, Paris, France. marie.prades@psl.aphp.fr
Golmard
Jean-Louis
JL
Vauthier
Danièle
D
Lefèbvre
Gilles
G
Poirot
Catherine
C
D000328:Adult; D015925:Cryopreservation; D010064:Embryo Implantation; D004624:Embryo Transfer; D004622:Embryo, Mammalian; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D011247:Pregnancy; D018873:Pregnancy Rate; D012189:Retrospective Studies; D016896:Treatment Outcome