A predictive model for high-quality blastocyst formation using Day 3 morphological scores in women of advanced maternal age.

OBJECTIVE

To develop and validate a simple predictive model based on Day 3 embryo morphology to guide blastocyst culture strategy and optimize transfer outcomes for women of advanced maternal age (AMA).

METHODS

This retrospective study analyzed a total of 6840 cleavage-stage embryos from 1102 fresh oocyte retrieval cycles with subsequent blastocyst culture in AMA patients. Key parameters including the number of oocytes retrieved, Day 2 and Day 3 cell numbers, embryo fragmentation, embryo grade, and the number of high-quality Day 3 embryos were assessed. Their associations with the blastocyst formation rate (BR), high-quality blastocyst formation rate (HBR) and clinical outcomes were evaluated.

RESULTS

Logistic regression identified the number of high-quality Day 3 embryos as a pivotal independent predictor. A threshold of ≥ 4 high-quality embryos was established. For cycles meeting this criterion, the risk of having no Day 5 transferable blastocyst was 19.30%. Within this group, Day 5 blastocyst transfer was associated with significantly higher clinical pregnancy and live birth rates, a lower multiple pregnancy rate, and improved neonatal outcomes (higher gestational age and birth weight) compared to Day 3 cleavage-stage transfer. The threshold showed good predictive performance in a temporally separated validation cohort (AUC 0.91).

CONCLUSION

In AMA patients, a threshold of ≥ 4 high-quality Day 3 embryos may serve as a practical, low-cost criterion to guide blastocyst culture and elective single blastocyst transfer. The approach is associated with favorable clinical and neonatal outcomes but requires prospective validation in unselected populations.