Hum. Reprod. Advance Access originally published online on October 10, 2007
Human Reproduction 2008 23(2):459; doi:10.1093/humrep/dem195
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Letters to the Editor |
On nucleation and implantation: 0% mononucleation or 100% mononucleation in blastomeres is not the whole story
IVF kliniken Cura, Box 20037, S-20074 Malmö, Sweden
1 Correspondence address. Tel: +46 40 987000; Fax: +46 40 987055; E-mail: per.sundstrom{at}curakliniken.se
We read with great interest the study by Scott et al. (2007)
on the importance of evaluating certain morphological parameters in zygotes and early embryos that related to outcome after IVF. One of the major findings of the study was that the nuclear status of an embryo has a strong impact on outcome after embryo transfer and that mononucleation in all blastomeres versus in no blastomere yielded a significant difference in pregnancy rates.
This finding is in agreement with our findings on the same issue. However, the pregnancy rate (implantation rate) in our study varied not only with all or none of the blastomeres in a four-cell embryo being mononucleate, but also with the percentage of blastomeres being mononucleate. In the study by Scott et al. (2007), pregnancies were achieved only when the embryo showed mononucleation either in all blastomeres or in none of the blastomeres. Thus, their study was only partly in accordance with our study. We find this confusing and wonder whether embryos that showed mononucleation in one, two or three blastomeres in a four-cell embryo were never used for transfer or if such embryos never implanted or if these categories of embryos were not recorded. We believe that these are important questions to clarify since our study, which constituted of single-embryo transfer cycles only, showed a significantly lower pregnancy rate not only in four-cell embryos lacking mononucleation, but also in four-cell embryos displaying mononucleation in one, two or three blastomeres only (20–22% pregnancy/implantation rate), in comparison with four-cell embryos with 100% mononucleation (42% pregnancy/implantation rate).
References
Scott L, Finn A, O'Leary T, McLellan S, Hill J. Morphological parameters of early cleavage-stage embryos that correlate with fetal development and delivery: prospective and applied data for increased pregnancy rates. Hum Reprod (2007) 22:230–240.
Saldeen P, Sundström P. Nuclear status of four cell preembryos predicts implantation potential in IVF treatment cycles. Fertil Steril (2005) 84:584–589.[CrossRef][Web of Science][Medline]
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