CORRELATION BETWEEN SPERM PENETRATION INTO THE HUMAN ZONA-PELLUCIDA AND IN-VITRO FERTILIZATION RATES

Sperm penetration into the zona pellucida of unfertilized oocytes, and its correlation with in vitro fertilization rates of the sibling oocy tes, were assessed. This was performed in order to evaluate the predic tion rate of the sperm penetration test into the zona pellucida. Unfer tilized oocytes (n = 1872) from 371 cycles were pipetted through a mic rocapillary, and the remaining sperm cells penetrating the zona pelluc ida were counted. The mean (+/- SD) number of spermatozoa that penetra ted the zona pellucida of unfertilized oocytes was 12.9 +/- 16.37. A s ignificant correlation was found between the fertilization rate and th e mean number of spermatozoa that penetrated into the zona pellucida o f the unfertilized sibling oocytes (r = 0.48; P < 0.001), or the perce nt of unpenetrated zonae pellucidae in a cohort (r = -0.43; P < 0.001) . However, a distinct-variation in the number of spermatozoa that pene trated into the zona pellucida was detected. A step-wise regression an alysis proved the number of spermatozoa penetrating the zona pellucida to be more predictive for fertilization rates than the variable of pe rcent of unpenetrated zonae pellucidae. The results imply that althoug h there is interdependence between penetration into the zona pellucida and fertilization rate, the predictive value of sperm penetration tes t for prognosis and future management after the first in vitro fertili zation attempt, is limited.