Rato, Mafalda; Gouveia-Oliveira, António; Plancha, Carlos E.
June 2010
Reproductive BioMedicine Online (Reproductive Healthcare Limited;Jun2010 S2 Supplement, Vol. 20, pS52
Academic Journal
Aim: Several factors have been proposed to influence human embryo freeze/thaw cryodamage, as well as the outcome of frozen embryo transfers (FET). At our center, the interesting observation that embryos thawed on the same day of transfer resulted in higher pregnancy rate lead us to retrospectively evaluate the influence of the post-thaw culture period on the implantation and developmental potential of cleavage stage embryos. Method: In this study, 265 FET cycles were allocated to one of two study groups, depending on the post-thaw culture period: (1) the long (18-24 h), or (2) the short (2-5 h) culture group. Groups were compared regarding implantation rate (IR) and live birth rate per embryo transferred (LBR/E). This statistical comparison was adjusted to possibly biasing factors such as: maternal age at oocyte pick-up, number of transferred embryos, developmental day at freezing, blastomere survival after thawing, catheter used for transfer and year of procedure. The importance of post-thaw mitosis assessment was also evaluated. Results: IR and LBR/E were inversely related to the post-thaw culture period, as the FET outcome after a short post-thaw culture period is significantly higher than after a long period (IR: 10.9% vs 4.9%, OR = 2.321, p = 0.039; LBR/E: 9.6% vs 2.9%, OR = 2.963, p = 0.035). This difference was not influenced by the possibly confounding factors mentioned above. Additionally, no advantage was found if only embryos with observed mitotic activity were transferred in comparison to transfers where mitotic resumption was not evaluated (IR: 6.5% vs 11.5%, OR = 1.985, p = 0.197; LBR/E: 5.2% vs 10.0%, OR = 1.966, p = 0.262). Conclusion: In this study we identified an association between a long post-thaw culture period and a loss of implantation and developmental potential of cleavage stage human embryos. Moreover, this study raises the interesting proposal that, in order to maintain acceptable post-thaw developmental potential, extending embryo culture should be avoided, even to document mitotic resumption.


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