title: Resumption of mitosis during post-thaw culture: a key parameter in selecting the right embryos for transfer.
abstract: This retrospective study of 701 thaw cycles analysed the clinical importance of whether or not embryos resumed mitosis during 24 h of post-thaw culture. A total of 3360 frozen embryos were thawed; 1922 embryos survived the freeze-thaw procedure with at least one intact blastomere and were then cultured for 24 h before transfer. All transfers were registered into either the 'cleaved embryo group' (n = 459), which was defined as transfers where at least one of the transferred embryos cleaved during the post-thaw culture period, or the 'non-cleaved embryo group' (n = 153), where none of the transferred embryos cleaved during the post-thaw culture period. A total of 1408 thawed embryos were transferred in 612 cycles; 459 embryo transfers were in the cleaved embryo group, resulting in an implantation rate of 10%, significantly higher than the 4% in the non-cleaved embryo group (P = 0.0003). A total of 130 pregnancies (28% per transfer) were obtained in the cleaved embryo group which was significantly higher than the 17 pregnancies (11% per transfer) obtained in the non-cleaved embryo group (P = 0.0001). However, the average number of transferred embryos was significantly higher in the cleaved embryo group (2.46 +/- 0.03) compared to the non-cleaved embryo group (1.82 +/- 0.07). No difference was found in the age of the women between the two groups. When analysing transfers where all transferred embryos had cleaved during the post-thaw culture period the clinical pregnancy rate increased significantly from 13% transferring two embryos to 36% transferring three embryos (P = 0.0136). In this latter subgroup an implantation rate as high as 17% was obtained. The overall multiple pregnancy rate was 16%. The multiple pregnancy rate was 19% in the cleaved embryo group. In conclusion, 24 h post-thaw culture may allow a better selection of the embryos and thereby we may be able to increase the implantation and pregnancy rates. This may enable us further to reduce the number of embryos transferred.
authors.affiliation: The Fertility Clinic, The Juliane Marie Center, Rigshospitalet, University of Copenhagen, Denmark.
authors.forename: S
authors.initials: S
authors.lastname: Ziebe
authors.forename: B
authors.initials: B
authors.lastname: Bech
authors.forename: K
authors.initials: K
authors.lastname: Petersen
authors.forename: A L
authors.initials: AL
authors.lastname: Mikkelsen
authors.forename: A
authors.initials: A
authors.lastname: Gabrielsen
authors.forename: A N
authors.initials: AN
authors.lastname: Andersen
mesh_terms: D000328:Adult; D002970:Cleavage Stage, Ovum; D015925:Cryopreservation; D046508:Culture Techniques; D010064:Embryo Implantation; D004624:Embryo Transfer; D005260:Female; D006801:Humans; D008423:Maternal Age; D008875:Middle Aged; D008938:Mitosis / Q000502:physiology*; D011247:Pregnancy; D011256:Pregnancy Outcome; D018566:Pregnancy, High-Risk; D011785:Quality Assurance, Health Care; D012189:Retrospective Studies; D013048:Specimen Handling / Q000379:methods*