Correlation of oocyte morphometry parameters with woman's age

Aim of this study was to evaluate morphometric parameters of metaphase II oocytes, including cytoplasm diameter (CD), zona pellucida thickness (ZPT) and width of the perivitelline space (PS), in relation with zona pellucida birefringence, spindle presence and age of the woman. Oocytes were classified into groups according to zona birefringence (low or high zona birefringence, LZB and HZB, respectively) and presence or absence of a visible spindle (SP and aSP, respectively). HZB oocytes showed a thicker zona (17.7 +/- 0.3 mu m) than LZB oocytes (16.7 +/- 0.3 mu m, p < 0.01). Moreover, PS was narrower in HZB and SP oocytes than in LZB (p < 0,001) and aSP (p < 0,05) oocytes. Finally, we found that CD and ZPT linearly decrease with age of the woman (CD r = 0.028: p < 0.01; ZPT r = 0.050: p < 0.0001). Our results evidence an association in human oocytes between zona pellucida and spindle birefringence and defined morphometric parameters and a decrease of oocyte size and ZPT as a function of women's age.