In 2020, Dr. Matthew A Shear, et al, reported in their retrospective cohort study* that the blastocyst morphological grade and the day of cryopreservation have less assessment value among euploid embryos identified by PGT-A. However, they are important parameters to identify the embryos with a higher live birth rate among the blastocysts which were not tested by PGT-A.
Among the non-PGT-A tested blastocysts, their data showed that
– Blastocysts cryopreserved on Day 6 had a lower live birth rate compared to those cryopreserved on Day 5;
– Blastocysts with an inferior pre-vitrification trophectoderm grade had a lower live birth rate compared to those of grade A (trophectoderm grade B versus A); and
– A higher pre-vitrification expansion grade was associated with a better chance of live birth (pre-vitrification expansion grade 5 versus 4)
*Blasts from the past: is morphology useful in PGT-A tested and untested frozen embryo transfers? Reprod Biomed Online. 2020 Dec;41(6):981- 989. doi:10.1016/j.rbmo.2020.07.014. )