Sperm penetration through the human zona pellucida as a predictor of in vitro fertilization

The aim of this study was to determine the predictive value of sperm penetration into the perivitelline space of human cadaveric oocytes on in vitro fertilization outcome. Forty-two patients with tubal infertility undergoing ovarian stimulation with gonadotropin for in vitro fertilization and embryo transfer participated in the study. The number of spermatozoa bound to the human zona pellucida, the percentage of cadaveric oocytes with one or more spermatozoa in the perivitelline space, and the in vitro fertilization outcome were evaluated. Spermatozoa from 37 of 42 patients were able to penetrate the perivitelline space of cadaveric oocytes as well as to fertilize human oocytes in vitro. In three individuals, no penetration of the perivitelline space of cadaveric oocytes was observed and no in vitro fertilization was detected. Only two patients were able to fertilize the couple's oocytes without penetration of the cadaveric oocytes. Based on these results the specificity and the sensitivity of the assay to predict in vitro fertilization was 100% and 94.1%, respectively. Accordingly, these results suggest that sperm-zona penetration is a useful bioassay to predict male fertility potential in IVF outcome.