Higher pregnancy rates after zona pellucida sperm selection

Abstract

To investigate the effectiveness of immobilized acid-solubilized zonae pellucidae in the selection of spermatozoa for intracytoplasmic sperm injection (ICSI). A prospective sibling oocytes study. In this study were included 113 couples who fulfilled the inclusion criteria: 1) unexplained infertility factor; 2) good quality oocytes; 3) fertilization failure for 3-5 consecutive ICSI procedures; 4) at least one oocyte at germinal vesicle stage (GV) and 5) at least four metaphase II oocytes retrieved during follicular puncture. Zonae pellucidae were isolated from the patient’s own GVs. Zonae were acid solubilized and diluted in carbonate buffer (pH 9.6) for air dry immobilization on glass petri dishes. The partner’s semen was washed and placed in the dishes. The spermatozoa that adhered on the immobilized surface were used for ICSI in the half of the retrieved oocytes from each woman. The other half of the oocytes was fertilized by conventional ICSI. In total, 312 oocytes were injected with zona-selected spermatozoa (zona-selection group) and 366 oocytes were injected with conventionally-selected spermatozoa (control group). The resulted embryos from the zona-selection and the control group were used in 43 and 50 single embryo transfers, respectively. Main outcomes were fertilization rate, embryo quality, implantation rate and pregnancy rate. Statistical analysis was performed using SPSS Software ver.21. Slightly higher fertilization rate was observed among the oocytes injected with zona-bound spermatozoa in comparison to the conventional ICSI group (75.6% vs. 72.3%, p=0.38). Also no significant differences were observed in the embryo quality and in the implantation rates between the zona-selection and the control group (p=0.24 and p=0.59, respectively). However, the pregnancy rate was considerably higher in the zona-selection group when compared with the control group (34.8% vs. 16.4%, p=0.02). Moreover the miscarriage rate also differed significantly (7% in zona-selection vs. 18% in control group, p=0.03). The use of patient’s zona pellucida immobilized proteins in selection of spermatozoa for ICSI increases pregnancy rates and reduces the risk of miscarriage in couples with unexplained infertility and good quality oocytes.