Does women’s age influence zona pellucida birefringence of metaphase ΙΙ oocytes in in-vitro maturation program?

BACKGROUND In vitro maturation (IVM) is a promising treatment option for certain infertile women. Nowadays, with the aid of PolScope, it has become possible to evaluate zona pellucida (ZP) characteristics as a parameter of oocyte quality. Moreover, quality of oocytes can be influenced by many factors, such as patient's age. The PolScope system is a non-invasive technique to assess birefringent structures such as the meiotic spindle and ZP in living oocytes. OBJECTIVE The aim was to determine the influence of the woman's age on ZP birefringence, a sign of oocyte quality, and morphology of in-vitro matured human oocytes using non-invasive polarized light (PolScope) microscopy. MATERIALS AND METHODS ZP birefringence and morphology were determined in 105 retrieved oocytes from 58 women undergoing ICSI in two age groups (≥30 years and <30 years). The immature oocytes were selected and after IVM, the quality of metaphase ΙΙ (MII) oocytes was assessed. The oocytes abnormalities were classified as intracytoplasmic and extracytoplasmic abnormalities. RESULTS Oocyte maturation rates were significantly reduced in ≥30 year's women (56%) in comparison with other age group (80.7%). In addition, the ZP birefringence was significantly higher in MII oocytes in the younger group compared with the older group (76.2% vs. 38.1%; p=0.00). Following morphologic assessment, the rates of oocytes with extracytoplasmic (p=0.02) and both abnormalities (extra- and intracytoplasmic) (p=0.01) were higher in aged versus the younger women. CONCLUSION There was a positive relationship between advanced maternal age with decreased ZP birefringence and oocyte morphological quality in in-vitro matured human oocytes.