Embryo morphology or cleavage stage: how to select the best embryos for transfer after in-vitro fertilization |
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Authors: | Ziebe S; Petersen K; Lindenberg S; Andersen AG; Gabrielsen A; Andersen AN |
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Institution: | The Fertility Clinic, The Juliane Marie Center, Rigshospitalet, University of Copenhagen, Denmark. |
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Abstract: | This retrospective study of 1001 in-vitro fertilization (IVF) cycles
included a consecutive series of single transfers (n = 341), dual transfers
(n = 410) and triple transfers (n = 250) where all the transferred embryos
in each cycle were of identical quality score and identical cleavage stage.
In our 2 day culture system, transfer of 4- cell embryos resulted in a
significantly higher implantation rate and pregnancy rate (23 and 49%)
compared with 2-cell embryos (12 and 22%) and 3-cell embryos (7 and 15%).
Furthermore, the transfer of 4-cell embryos resulted in a significantly
higher pregnancy rate compared with embryos that had cleaved beyond the
4-cell stage (28%). The implantation rate (21%) and pregnancy rate (43%)
after transfer of embryos of score 1.0 were significantly higher than after
transfer of embryos of score 2.0 (14 and 32% respectively). Transferring
embryos of score 2.1 resulted in significantly higher implantation rates
(26%) and similar pregnancy rates compared with score 1.0. Transferring
embryos of score 2.2-3.0 resulted in a significantly lower implantation
rate (5%) and pregnancy rate (15%). A striking finding was that embryos of
quality score 2.0 had a significantly lower implantation rate compared with
embryos of quality score 1.0 and 2.1 and a significantly lower pregnancy
rate compared to embryos of quality score 1.0. We also found a lower
implantation rate and pregnancy rate when transferring 3-cell embryos.
These findings may indicate periods of increased sensitivity to damage
during the cell cycle. In conclusion, these results substantiate the idea
of the superiority of 4-cell embryos and demonstrate that minor amounts of
fragments in the embryo may not be of any importance. These findings may
call for a shift when weighing the two main morphological components
(quality score and cleavage stage) in the sense that reaching a 4-cell
cleavage stage even with the presence of a minor amount of fragments should
be preferred to a 2-cell embryo with no fragments.
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