Blasts from the past: Is morphology useful in both PGT-A tested and untested frozen embryo transfers?

ABSTRACT RESEARCH QUESTION Day of cryopreservation, inner cell mass (ICM) grade, trophectoderm (TE) grade and blastocyst expansion grade have been associated with differences in live birth rate in frozen embryo transfer (FET) cycles. We sought to examine the likelihood of live birth and whether blastocyst morphologic grade is more or equally useful in FET cycles among PGT-A tested and untested blastocysts. DESIGN Retrospective cohort study of 6,271 vitrified-warmed, autologous, single embryo transfer cycles among patients undergoing in vitro fertilization (IVF) from July 2013 to December 2017 at a single, university-affiliated infertility practice. The primary outcome was live birth, calculated by generalized estimating equation. RESULTS Among PGT-A tested embryos, we observed inferior ICM grade was associated with lower chance of live birth (ICM grade B vs. A aRR: 0.96; 95%CI: 0.84-0.99). Among untested blastocysts there was a lower live birth rate in blastocysts cryopreserved day 6 versus day 5 (aRR: 0.87; 95% CI: 0.78-0.96), inferior pre-vitrification TE grade (TE grade B Vs. A aRR: 0.86; 95% CI: 0.79-0.94), and blastocysts with a higher pre-vitrification expansion grade (grade 5 vs. 4 aRR: 1.1; 95% CI: 1.01-1.2), but ICM grade was not associated with chance of live birth (grade B vs. A aRR: 0.93 95%; CI: 0.86-1.02). CONCLUSIONS Among PGT-A untested blastocysts, assessing embryo quality by day of cryopreservation, TE grade and expansion grade may help identify embryos with the highest likelihood of live birth. Identifying euploid embryos by PGT-A appears to homogenize the cohort, making blastocyst morphologic grade and the day of cryopreservation less important. STUDY FUNDING/COMPETING INTEREST(S) This work was conducted with support from Harvard Catalyst | The Harvard Clinical and Translational Science Center (National Center for Research Resources and the National Center for Advancing Translational Sciences, National Institutes of Health Award UL1 TR001102) and financial contributions from Harvard University and its affiliated academic health care centers. The funding sources had no involvement in the study design, collection, analysis, or interpretation of data, the writing of the report, or the decision to submit the article for publication.