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Fertil Steril. 2005 Jan;83(1):49-53.

Blastocyst culture after repeated failure of cleavage-stage embryo transfers: a comparison of day 5 and day 6 transfers.

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Center for Reproductive Medicine and Fertility, Quirón Bilbao, Bilbao, Spain.



To evaluate the efficacy of blastocyst transfer among patients with at least three previous cleavage-stage embryo transfer failures and to compare pregnancy and implantation rates of blastocysts according to the day of embryo transfer (day 5 or day 6 after oocyte retrieval).


Retrospective clinical study.


Private ART center.


One hundred forty-eight patients (with at least three failed cleavage-stage embryo transfers) undergoing blastocyst-stage embryo transfer.


Embryos were grown for up to 6 days and only blastocyst-stage (cavitating) embryos were transferred on either day 5 or day 6 after oocyte retrieval.


Clinical pregnancy and implantation rates.


Blastocysts transferred on day 5 implanted almost five times the rate of those transferred on day 6 (23% vs. 5%). Pregnancy rates were triple as high among the 73 day 5 patients compared to the 63 day 6 transfer patients (38% vs. 11%). The number of blastocysts formed and per embryo rates of blastocyst formation were both significantly higher for patients undergoing day 5 transfers: more blastocysts developed (3.0 vs. 2.1) and more were transferred (3.0 vs. 1.9). In addition, blastocyst formation rates were 46% and 33%, respectively, for both groups of patients.


Blastocyst transfer (preferably on day 5 after retrieval) appears to be a successful and improved alternative for patients with multiple failed IVF attempts. Moreover, with blastocyst transfer there should be a reduction in multiple pregnancy risk, because fewer embryos have to be transferred.

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