Daniela Demetrio (RuAnn Genetics, Caruthers, CA)
Jennifer Barfield (Colorado State University, Fort Collins, CO)
Grade 1 COCs have more than 3 complete and compact layers of cumulus cells covering the surface of the
zona pellucida (ZP). The ooplasm is dense and has even granulation.
Grade 2 COCs have 1 or 2 compact cumulus cell layers covering the surface of the ZP and the ooplasm is
dense with even granulation. Grade 1 oocytes with speckled ooplasm are downgraded to grade 2.
Grade 3 COCs have less than 1 complete layer of cumulus cells covering the surface of the ZP. Grade 2
oocytes with speckled ooplasm are downgraded to grade 3.
Grade 4 COCs have expanded cumulus cell layers, often with an agglutinated appearance. Grade 3 oocytes with speckled ooplasm are downgraded to grade 4. If the ooplasm is retracted, the oocyte will be
considered degenerated.
Degenerated COCs consist of oocytes with retracted or noticeably light and/or speckled ooplasm, fused
cumulus cells, or cracked and/or empty ZP.
IETS Guidelines – October 2022
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