Abstract
Purpose
To assess the variables that may predict which cleavage-stage embryo may develop into a blastocyst, and vice versa, to determine whether the cleavage-stage embryo morphology should be taken into consideration when transferring the embryo at the blastocyst stage.
Methods
A single center, retrospective cohort study. The study cohort included 3072 patients undergoing 3607 retrieval cycles and 23,124 embryos at the cleavage stage. We assessed the blastulation rate and evaluated which variables impact the ongoing pregnancy rate.
Results
High blastulation rate correlates with higher embryos' grading (I > II > III > IV > V) and higher number of blastomeres (8 > 7 > 6 > 5 > 4). 949 patients had fresh single blastocyst transfers. The ongoing pregnancy rate was 28.9% per transfer. Patients with ongoing pregnancies were significantly younger (34.3 vs. 36 years, p < 0.001), had higher number of oocyte yield (9.8 vs. 9, p = 0.02), and an increased rate of good-quality embryos transferred (70.7% vs. 47.7%, p = 0.001). When evaluating embryos progression, we found that whenever embryo developed to a good-quality blastocyst, its appearance at the cleavage stage did not affect ongoing pregnancy rate.
Conclusion
Higher the number of blastomeres and better embryo grading were found to correlate with a higher blastulation rate. Nevertheless, if the embryo has already developed to a top-quality blastocyst, its morphology at the cleavage stage did not impact ongoing pregnancy rate.
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EZ: principal investigator, designed the study, wrote the paper and edited it in all its revisions. RC and RO: participated in designing the study, retrieved the data, performed the statistical evaluations, proof read the paper and took part in discussions regarding the results. AV: retrieved the data, proof read the paper and took part in discussions regarding the results. EB: retrieved the data, proof read the paper and took part in discussions regarding the results. JM: retrieved the data, proof read the paper and took part in discussions regarding the results. JH: participated in designing the study, assisted in writing the paper and edited it, proof read the paper and took part in discussions regarding the results.
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The authors report no conflict of interest.
Ethical approval
The study protocol was approved by the Institutional Review Board, Veritas IRB 16304-17 on February 5th, 2019.
Informed consent
It was a retrospective study and therefore informed consent was not needed. This retrospective study included 3607 women undergoing IVF during the years 2016–2018 and the patients are not ongoing treatments in the present. We collected the data from our databases and did not perform any intervention.
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Zilberberg, E., Casper, R., Meriano, J. et al. Cleavage vs blastocyst stage embryos: how are they interrelating?. Arch Gynecol Obstet 304, 1083–1088 (2021). https://doi.org/10.1007/s00404-021-06003-z
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DOI: https://doi.org/10.1007/s00404-021-06003-z