The association of the blastomere volume index (BVI), the blastomere symmetry index (BSI) and the mean ovality (MO) with ongoing implantation after single embryo transfer

Purpose

To generate novel, objective variables that resemble embryo quality and relate them to ongoing implantation, using multilevel imaging of single-transferred embryos.

Methods

Retrospective analysis of multilevel images of 659 day 3 single-transferred embryos. Each embryo was photographed on seven different levels, in order to measure the largest diameter of every blastomere within an embryo. The volume of each blastomere was calculated using the equation $ 1/6pi ^*mathrm{diamete}{{mathrm{r}}^3} $ . The blastomere volume index (BVI) represented the ratio between the total blastomeric volume of an embryo and the mean cytoplasmic volume of an oocyte on day 0. The blastomere symmetry index (BSI) represented the ratio between the greatest blastomere volume and the smallest blastomere volume within an embryo. The mean ovality (MO) represented the presence of non-spherical blastomeres. Analyses were performed to compare the BVI, BSI and MO between patients with and without an ongoing implantation.

Results

The mean BVI was significantly higher for embryos in the ongoing implantation group compared to the no ongoing implantation group. The mean BSI was associated with ongoing implantation for unevenly cleaved embryos. The MO of blastomeres within an embryo was similar for embryos in the ongoing implantation group compared to the no ongoing implantation group. The association of the BVI and BSI with ongoing implantation was confounded, because only female age and cleavage rate were significantly associated with ongoing implantation in multiple logistic regression analyses.

Conclusions

The BVI, BSI and MO are objective variables that resemble embryo quality, but they are not suitable to use as embryo selection tools.