Objective: To investigate the role of the cell number at day 3 in blastocyst selection.
Design: Observational, retrospective, single-center clinical study.
Patient(s): In part 1, 1211 single vitrified-warmed blastocyst transfer (SVBT) cycles were identified and reviewed. All the cycles were conventional in vitro fertilization (IVF) cycles and the first embryo transfer cycles. Most of patients had a risk of ovarian hyperstimulation syndrome and were young. In part 2, 864 IVF-derived blastocysts from 292 infertile couples underwent trophectoderm (TE) biopsy for preimplantation genetic testing for aneuploidies (PGT-A).
Intervention(s): No patient intervention.
Main outcome measure(s): The first part was an analysis of the correlation between the cell number at day 3 and live birth rate (LBR) after SVBT, and the second part was an analysis of the correlation between the cell number at day 3 and euploid rate (ER) of blastocysts.
Result(s): In part 1, after correcting for the effects of other confounders, the cell number at day 3 had no significant effect on the LBR (OR 1.001, 95% CI 0.938-1.068). In part 2, after correcting for the effects of other confounders, the cell number at day 3 had no significant effect on the ER (OR 0.960, 95% CI 0.866-1.063).
Conclusion(s): When the vitrified-warmed blastocysts obtained by conventional IVF are transferred into young patients, the cell number at day 3 is not a strong predictor of the LBR. In addition, the cell number at day 3 is not a strong predictor of ER of IVF-derived blastocysts too.
Keywords: Blastocyst selection; Cell number; Euploid rate; Live birth rate.