Morphometric assessment of blastocysts: Relationship with the ongoing pregnancy rate

Open AccessPublished:November 10, 2022DOI:
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      Structured Abstract


      To explore a morphometric grading system for blastocysts that is associated with ongoing pregnancy.


      Cross-sectional study.


      All consecutive vitrified blastocysts at our center from July 2018 to November 2021 that were transferred in single blastocyst transfer cycles until January 2022.



      Main Outcome Measures

      The ongoing pregnancy rate after single vitrified-warmed blastocyst transfer. Interobserver agreement on morphometric values among embryologists.


      Three morphometric variables (blastocyst diameter, area of inner cell mass (ICM), and the estimated trophectoderm cell count), were used to evaluate the expansion, ICM, and trophectoderm morphology. During the study period, 585 blastocysts were involved in this study. Of the three morphometric variables, ICM area (per 500 μm2, adjusted OR 1.19, 95% CI [1.09−1.30], P<0.001) and estimated trophectoderm cell count (per 10 cells, adjusted OR 1.25, 95% CI [1.12−1.39], P<0.001) were significantly associated with the ongoing pregnancy rate after adjustment for confounding factors. The ongoing pregnancy rate was 2.0% (1/49) with an ICM area of <2,500 μm2 and the estimated trophectoderm cell count <70. The ongoing pregnancy rate reached 47.8% (22/46) when the ICM area and the estimated trophectoderm cell count were >3,500 μm2 and >110, respectively. Interobserver agreement on the blastocyst diameter, ICM area, and the estimated trophectoderm cell count was excellent-to-good among five embryologists (intraclass correlation coefficients [ICC]: 0.99, 0.87, and 0.91, respectively).


      Morphometric values of ICM and trophectoderm are promising predictors of pregnancy success. The high reproducibility suggests that the morphometric variables will contribute to identifying blastocysts with the highest developmental potential as well as those that will not result in a successful pregnancy.