Late-stage vacuolization as a compaction-dependent prognostic marker for day 4 embryo selection

Area of Science:

• Embryology
• Reproductive Medicine
• In Vitro Fertilization (IVF)

Background:

• Assessing Day 4 embryo quality is crucial for IVF success.
• Late-stage vacuolization is a morphological feature observed in developing embryos.
• Compaction status is a key indicator of early embryonic development.

Purpose of the Study:

• To evaluate the prognostic value of late-stage vacuolization in Day 4 embryos.
• To determine the relationship between vacuolization, compaction status, and blastocyst formation.
• To explore the potential of integrating vacuolization into embryo grading systems.

Main Methods:

• Retrospective analysis of 9,779 embryos from 2,409 patients undergoing fresh Day 4 transfers.
• Stratification of embryos by compaction status (full, part, non-compaction) and assessment of vacuolization.
• Evaluation of predictive performance for blastocyst formation using ROC curves and logistic regression.

Main Results:

• Late-stage vacuolization correlated with advanced maternal/paternal age, increased gonadotropin dosage, and lower AMH/estradiol.
• In the non-compacted subgroup, vacuolization significantly increased transferable (OR=3.34) and high-quality blastocyst rates (OR=2.51).
• Conversely, vacuolization decreased high-quality blastocyst formation in the fully compacted subgroup (OR=0.37) and had no significant effect on transferable blastocysts.

Conclusions:

• Late-stage vacuolization is a compaction-dependent prognostic marker in Day 4 embryos.
• Vacuolization is detrimental in compacted embryos but potentially beneficial in non-compacted ones.
• Context-specific integration of vacuolization into Day 4 embryo grading systems is recommended.