Blastocyst re-expansion 1 hour after biopsy: an independent predictor of live birth

Objective

In non–preimplantation genetic testing cycles, the recommended practice of blastocyst artificial collapse before vitrification has gained prominence, enhancing the viability of cryopreserved embryos (1). In preimplantation genetic testing for aneuploidy (PGT-A) cycles, artificial collapse is caused by the biopsy procedure itself, and the approach becomes more complex. The European Society of Human Reproduction and Embryology recommends immediate vitrification after biopsy for PGT-A cycles,

Study design

The cohort study included all women who underwent a single euploid blastocyst transfer between April 2021 and February 2023. Preimplantation genetic testing for monogenic disorders or structural rearrangements was excluded. Blastocysts were scored 1 hour after trophectoderm biopsy as follows: 0 for complete collapse; 1 for starting re-expansion; and 2 for clear re-expanded cavity (Supplemental Fig. 1, available online). The same grading criteria were used for assessing re-expansion 1 hour after

Results

Of 1,141 transfers from 937 couples, 569 (49.8%) resulted in LB (Supplemental Table 1, available online). When observed at 1 hour after biopsy, 730 blastocysts (64.0%) re-expanded to grade 2, 334 (29.3%) re-expanded to grade 1, and 77 (6.7%) did not re-expand at all (grade 0). Top- and good-quality blastocysts that re-expanded to grade 2 at 1 hour after biopsy had significantly higher LB rates than those that re-expanded to grades 1 and 0 (56.2% vs. 48.5% and 42.1%, respectively; P=.006;

Conclusion

Re-expansion grade at 1 hour after biopsy is associated with postwarming blastocyst re-expansion and increased LB rates. Standardizing the vitrification timing after biopsy and using re-expansion grade at the time of vitrification could enhance the selection process of euploid embryos and potentially improve first-transfer LB rates. The significant correlation between blastocyst re-expansion 1 hour after biopsy and subsequent re-expansion after warming merits additional research as strong