Correlation between morphological abnormalities in the human oocyte zona pellucida, fertilization failure and embryonic development

Objective: The general patient condition, oocyte and embryo condition and clinical outcomes were studied in patients with a morphologically abnormal zona pellucida (ZP). Methods: The general embryo condition was compared between patients with a morphologically abnormal ZP or a normal ZP. The general embryo conditions in the first and subsequent cycles were compared in patients with a morphologically abnormal ZP. Results: Oestradiol (E2) levels were higher in patients with an abnormal ZP than in those with a normal ZP (P<0.05). In the process of promoting ovulation, luteinizing hormone (LH) levels were higher in patients with an abnormal ZP than in those with a normal ZP (P<0.05). The MII rate was significantly lower in patients with a morphologically abnormal ZP than in patients with a normal ZP (P<0.05). After performing intracytoplasmic sperm injection (ICSI), the 2PN fertilization rate and pregnancy rate were significantly lower in patients with a morphologically abnormal ZP than in those with a normal ZP (P<0.05). The gonadotrophin (Gn) dosage for patients with a morphologically abnormal ZP was significantly higher in the second IVF cycle than in the first cycle. The MII rate, 2PN fertilization rate, and pregnancy rate were also significantly higher in the second cycle than in the first cycle (P<0.05). The perivitelline space was smaller within oocytes with a morphologically abnormal ZP than within those with a normal ZP (P<0.05), but the ZP was thicker than normal (P<0.05). Conclusions: Oocytes with a morphologically abnormal ZP had lower maturity, and ICSI can improve the fertilization rate of these oocytes. The application of a modified scheme improved ovum maturation, the fertilization rate, and the pregnancy outcome.