Developmental potential of different embryos on day 3: a retrospective study

Area of Science:

• Reproductive Medicine
• Embryology
• Assisted Reproductive Technology (ART)

Background:

• Accurate evaluation of day 3 (D3) embryos is crucial for predicting developmental potential.
• Morphological parameters like blastomere count, fragmentation, and symmetry are used, but criteria vary.
• Existing studies show conflicting results when combining these parameters for embryo evaluation.

Purpose of the Study:

• To investigate the impact of different Day 3 embryo quality grades on blastocyst formation and clinical outcomes.
• To redefine D3 embryo evaluation criteria and analyze their correlation with developmental potential and IVF success.
• To provide guidance for embryologists in selecting embryos for transfer and predicting IVF cycle outcomes.

Main Methods:

• Retrospective analysis of 699 patients undergoing ART between January 2017 and February 2021.
• Extended culture of 2517 D3 embryos to assess blastocyst development (Day 5 and Day 6).
• Classification of D3 embryos into five grades (A-E) based on cell number, blastomere symmetry, and fragmentation percentage.

Main Results:

• Grade C embryos (>10 cells, symmetrical, <20% fragmentation) demonstrated higher Day 5 blastocyst formation and high-quality blastocyst rates (p<.05).
• Grade A embryos (6-10 cells, symmetrical, <20% fragmentation) achieved significantly higher clinical pregnancy rates (p<.05).
• Embryos with less fragmentation and ≥6 symmetrical blastomeres showed higher developmental potential; 6-10 cell embryos yielded ideal clinical outcomes.

Conclusions:

• D3 embryo morphology, specifically cell number and symmetry, influences blastocyst development and clinical pregnancy rates.
• Grade A embryos offer better clinical outcomes, while Grade C embryos exhibit superior blastocyst development potential.
• The findings support refined D3 embryo assessment for improved embryo selection and IVF success prediction.