Blastocysts from partial compaction morulae are not defined by their early mistakes

Area of Science:

• Reproductive biology
• Embryology
• Genetics

Background:

• Morula formation involves compaction, where blastomeres adhere to form a solid sphere.
• Partial compaction, where not all blastomeres are included, is a less understood phenomenon.
• The developmental implications of partial compaction are unclear.

Purpose of the Study:

• To investigate if partial compaction during morula formation is linked to embryo developmental capacity and implantation potential.
• To compare reproductive outcomes between embryos with full and partial compaction.

Main Methods:

• Retrospective analysis of 196 preimplantation genetic testing for aneuploidy (PGT-A) cycles.
• Embryos were categorized into full or partial compaction groups based on blastomere inclusion.
• Morphokinetic parameters, blastocyst formation, morphology, and cytogenetic constitution were compared.
• Reproductive outcomes and chromosomal concordance were assessed.

Main Results:

• Partial compaction occurred in 49.3% of embryos, with no association with maternal age or ovarian response.
• Embryos with partial compaction exhibited altered morphokinetics and a lower blastocyst formation rate (57.2% vs. 70.8%).
• However, euploidy rates (38.4% vs. 34.2%) and live birth rates (51.9% vs. 46.2%) were equivalent between partial and full compaction groups.

Conclusions:

• Partial compaction is associated with reduced embryo developmental ability.
• Despite developmental differences, blastocysts from both partial and full compaction groups yield similar euploidy rates and reproductive outcomes.
• Cell exclusion during compaction may signal compromised embryo development, independent of chromosomal status.