Alternative patterns of partial embryo compaction: prevalence, morphokinetic history and possible implications

Area of Science:

• Embryology
• Reproductive Medicine
• Developmental Biology

Background:

• The morula stage is critical but poorly understood in human embryonic development.
• Cell compaction during the morula stage can be complete or partial, with unknown implications.

Purpose of the Study:

• Investigate the prevalence of partial compaction during the human morula stage.
• Elucidate the morphokinetic mechanisms and developmental consequences of partial compaction.

Main Methods:

• Analysis of preimplantation genetic testing for aneuploidies (PGT-A) cycles using time-lapse technology.
• Observation of embryo development from biopsy to blastocyst stage in three age groups (≤34, 35-39, ≥40 years).

Main Results:

• Identified three compaction modalities: full compaction (FCM), excluded partial compaction (excluded-PCM), and extruded partial compaction (extruded-PCM).
• Partial compaction was more frequent than full compaction; excluded-PCM showed slower morphokinetics and abnormal cleavage.
• Embryo degeneration was linked to cell extrusion; loss of cells in excluded-PCM affected blastocyst rates.
• Aneuploidy rates showed no difference across groups in younger women, but differences were observed in women aged ≥40.
• Implantation rates of euploid blastocysts did not differ significantly between compaction groups.

Conclusions:

• Detected distinct patterns of incomplete embryo compaction with varying morphokinetic behaviors.
• These compaction patterns are associated with different developmental potentials and outcomes.