FROM SUBJECTIVE GRADING TO QUANTITATIVE METRICS: EVALUATING THE PREDICTIVE VALUE OF MORPHOMETRIC MEASUREMENTS OF THE INNER CELL MASS AND TROPHECTODERM IN FROZEN EMBRYO TRANSFER CYCLES

Abstract

Background. Blastocyst selection for frozen embryo transfer (FET) still relies overwhelmingly on the subjective Gardner grading system, which suffers from substantial “inter- and intra-observer variability” in addition to compresses continuous biological variation into a few ordinal categories. Whether objective morphometric measurement of “the inner cell mass (ICM) and trophectoderm (TE)” improves outcome prediction has not been characterised in an Indian FET population. Objective. To compare the predictive value of quantitative digital morphometry of the ICM and TE with conventional Gardner grading for live birth after single vitrified–warmed blastocyst transfer. Methods. Retrospective cohort of 412 single autologous vitrified–warmed blastocyst transfers. Seven morphometric parameters were measured from calibrated pre-transfer images in ImageJ by observers blinded to outcome. The “primary outcome was live birth. Discrimination was assessed by area under the receiver-operating-characteristic curve (AUC)”; independent associations by multivariable logistic regression; and reproducibility by intraclass correlation (ICC) versus weighted κ. Results. The live birth rate was 40.8% and clinical pregnancy rate 54.6%. ICM area (AUC 0.69), ICM diameter (0.69), blastocyst area (0.68) and TE cell number (0.67) each out-performed the Gardner composite grade (0.63). A combined four-parameter morphometric “”model achieved an AUC of 0.71, significantly higher than Gardner grading (0.63; p = 0.003). ICM area (adjusted OR 1.31 per 500 µm²; 95% CI 1.11–1.54) and “TE cell number (aOR 1.08 per cell; 95% CI 1.01–1.15) were independent predictors” of live birth. Live birth rose monotonically across ICM-area tertiles (23.2% → 39.4% → 59.9%). Objective morphometry was far more reproducible (ICC 0.88–0.96) than subjective grading (κ 0.52–0.64). Conclusion. Quantitative morphometry of the ICM and TE provides discrimination modestly superior to — and markedly more reproducible than — subjective Gardner grading for live birth after FET. Continuous morphometric metrics are a low-cost, scalable adjunct to embryo selection well suited to high-volume Indian ART practice.