Background: Conflicting results have been reported regarding the use of polarized microscopy as a predictive tool for human oocyte quality.
Methods: Oocytes from 121 ICSI cycles were analysed with polarized microscopy. Both qualitative (spindle presence) and quantitative (retardance) data were correlated to the key assisted reproduction technology outcome parameters. Second, polarized microscopy was applied on in vitro matured (IVM) oocytes from germinal vesicle oocytes that matured after 24 or 48 h and from metaphase I oocytes matured after 3 or 24 h. These data were correlated with confocal analysis of spindle-chromosome complex.
Results: Spindles were detected in 82% of in vivo matured oocytes and in 64% adjacent to the first polar body (PB). Fertilization rate was higher in oocytes with a visible spindle (P = 0.0002). In patients aged over 35 years, the percentage of a visible spindle and mean spindle retardance was lower than in younger patients (P < 0.03). A higher number of spindles were located adjacent to the first PB in IVM matured oocytes (94%) versus in vivo matured oocytes (P < 0.0001). Confocal imaging revealed that spindle absent IVM metaphase II (MII) oocytes had a higher degree of aberrant spindle and chromosomal configurations versus IVM MII oocytes with a visible spindle (P = 0.002).
Conclusions: Oocytes with absent spindles were associated with lower fertilization rates and advanced female age. Other important outcome parameters (embryo quality, pregnancy rates) were not correlated to spindle nor zona inner layer analysis. Interestingly, confocal imaging showed that polarized microscopy might be used as a qualitative predictive tool of human oocyte quality but no correlation could be demonstrated with quantitative polarized microscopy.