Table 1.
Summary of the morphological and visual indicators of oocyte competence.
| Reference | Criteria | Recommendation |
|---|---|---|
| [28,30,31] | Ovarian morphology | Presence of cycle-related structures |
| [7,33,34,35] | Follicle size | >5 mm |
| [30,49,50] | Morphology of the cumulus–oocyte complexes (COCs) | COCs with at least five layers of cumulus cells (CC), compact and/or slightly expanded cumulus, with or without dark spots in the oocyte and cumulus |
| [53,67,68] | Lipid content | Dark ooplasm indicates high competence, light-colored indicates lacking lipids and poor competence, and black ooplasm indicates aging |
| [77,78,79,80] | Cumulus expansion and oocyte size | Not associated to oocyte quality; important role in fertilization |
| [29,83,86,135] | Oocyte size | Diameters >115 and <130 microns |
| [96,97,98,99] | First polar body (PB1) morphology | PB1 of a homogeneous, round shape with a smooth or intact surface |
| [112,114,115] | Meiotic spindle and zona pellucida birefringence | Useful tool for micromanipulation procedures (intracytoplasmic sperm injection (ICSI) or somatic cell nuclear transfer (SCNT)) and for assessing post-warming integrity of meiotic spindle of vitrified bovine oocytes |
| [121,122] | Zona pellucida birefringence (ZPB) | Lower ZPB is related to high quality oocytes and improved blastocyst development |
| [115,128,129,130,134] | Brilliant cresyl blue staining | BCB+ oocytes have higher developmental competence than BCB− oocytes |