Selection of Blastocysts for Transfer Using a Quantitative Bioassay of Blastocoel Expansion Rather than Standard Morphology Grading - Abstract
Abstract Recent evidence has shown a sustained singleton pregnancy benefit using trophectoderm biopsy and preimplantation genetic testing for euploidy. However, these results have utilized conventional standard grading morphology for the selection of the blastocysts actually selected for transfer. This approach is subjective and difficult to standardize. We describe here a new selection method using a non-invasive, physiological assay of blastocyst expansion using time lapse imaging. Using this technique, blastocysts can be objectively ranked within cohorts for transfer based upon objective and quantitative measurements of expansion rates which is completely independent of standard grading. Results described here show that prospective selection of first blastocysts for transfer using this approach results in identical and high live birth pregnancy rates from either biopsied or unbiopsied blastocysts in younger patients <37yrs (73.6% vs 74.5%, respectively). For patients >37yrs, similar pregnancy rate parity was achieved between single euploid blastocysts using the two highest ranked unbiopsied blastocysts and with little twin risk (62.1% vs 60.1%). Unexpectedly, the results in the older age group show evidence for a significant reduction in pregnancy rate using biopsy on an intention to treat basis. This reduction (from 62.1% to 29.0%) may be explained by a masking of some blastocyst’s normal totipotentiality by biopsy results that do not reflect true meiotic whole chromosome aneuploidy (e.g. segmental and/or mosaic results). Such cases were more prevalent in patients having smaller blastocyst cohort sizes (<4). While results from subsequent transfers from cohorts have yet to be assessed, this new prospective approach to using blastocyst expansion rate assessment represents a rational tool for the identification of individual blastocysts with the highest likelihood for euploidy without the need invasive biopsy and genetic analysis.