Zona pellucida (ZP)

The thickness of the ZP may vary from <15 µm to > 20 µm. It may also present a septum or a dark color.


PVS may be large or nearly absent. It may contain fragments.


First polar body (PB1)

PB1 is considered as normal when it is ovale and intact, with a smooth or rough surface. Fragmented or giant PB is considered as abnormal.


Cytoplasmic inclusions and clusters

  • vacuoles: fluid-filled refrigent round cavities. They may be isolated or numerous.
  • refractile body: inclusions of different sizes containing lipofucsin
  • smooth endoplasmic reticulum (SER) cluster: appears as a flat elliptical disk in the centre of the ooplasm
  • dark cluster: cluster of organelles that appears as a dark area in the ooplasm


Cytoplasmic granularity gradients

Granulated area are frequently observed in the animal (PB1 region) or vegetal poles (opposite to the animal pole) but also in a meridionnal region extending from the vegetal to the animal pole.


Effects of various phenotypes on embryo development and implantation

The influence of the different oocyte phenotypes on embryo development and implantation is still controversial. Some dysmorphic morphological features may represent phenotypic variability without any consequences on development.

Parameters Effect on implantation
ZP abnormality Controversial
PVS size Controversial
PVS fragments Controversial
PB morphology Controversial
SER Detrimental if severe
Vacuoles Detrimental if severe
Refractile bodies Detrimental if severe
Dark clusters Detrimental if severe



Balaban B and Urman B. Effect of oocyte morphology on embryo development and implantation. RBMonline 12: 608-615, 2006