A predictive model for early blastocyst formation in 2,557 patients undergoing fresh Day 4 embryo transfer.

This retrospective cohort study was conducted at Xingtai MeiHe Reproductive and Genetic Hospital involving 2,557 patients scheduled for fresh Day 4 embryo transfer. The primary objective was the development and validation of a predictive model for early blastocyst formation on Day 4 post-fertilization. The study assessed associations between Day 3 embryo characteristics, specifically the number of blastomeres, and subsequent blastocyst development.

The analysis identified that Day 3 embryos with more than 10 blastomeres were associated with early blastocyst formation. The adjusted odds ratio was 1.668 in the training set and 1.369 in the validation set. The predictive model achieved an area under the curve (AUC) of 0.782 (95% CI: 0.738–0.826) in the training set and 0.773 (95% CI: 0.705–0.841) in the validation set.

Performance metrics included a sensitivity of 65.4% to 65.9% and a specificity of 79.6% to 81.7%. Clinical net benefits were confirmed across various threshold probabilities. No adverse events, serious adverse events, discontinuations, or tolerability data were reported. Key limitations include the retrospective design, lack of reported p-values for primary associations, and the absence of external validation beyond the internal validation set.

While the model shows promise for predicting early blastocyst formation, the observational nature of the study precludes causal inference. Clinicians should consider these results as supportive of existing morphological assessments rather than a standalone diagnostic tool until further prospective validation is available.