Correlation of sperm penetration assay score with polyspermy rate in in-vitro fertilization

BACKGROUND: The sperm penetration assay (SPA) is used to predict the fertilizing capacity of sperm. Thus, some programs rely on SPA scores to formulate insemination plans in conjunction with in-vitro fertilization (IVF) cycles. The purpose of this study was to evaluate if a relationship exists between SPA scores and polyspermy rates during conventional IVF cycles. METHODS: A total of 1350 consecutive IVF patients using conventional IVF insemination were evaluated in the study. Oocytes were inseminated three hours post-retrieval by the addition of 150,000 to 300,000 progressively motile sperm. Approximately 18 hours after insemination, the oocytes were evaluated for fertilization by the visualization of pronuclei. The presence of three or more pronuclei was indicative of polyspermy. Polyspermy rates, fertilization success, embryo quality, and pregnancy rates were analyzed retrospectively to evaluate their relationship with SPA score, count, motility, number of progressively motile sperm inseminated, oocyte pre-insemination incubation time, patient age, and diagnosis. RESULTS: A significant positive relationship was observed between SPA score and polyspermy rate (r(s )= 0.10, p < 0.05). Patients with a normal SPA score had significantly higher polyspermy rates than those with abnormal SPA scores (6.3% ± 1.5% vs. 2.0% ± 0.7%, p < 0.05). Fertilization percentage was significantly lower in the group with severely abnormal SPA scores versus all other SPA groups (57.5% ± 2.1% vs. 70.2% ± 1.3%, p < 0.005). Although embryo quality was not affected, both clinical pregnancy and implantation rates improved slightly as SPA score increased. In addition, there was a decrease in the rate of spontaneous abortion as SPA score increased. CONCLUSIONS: These data indicate SPA score is positively correlated with polyspermy rates and IVF fertilization percentage. Additionally, there is a slight increase in clinical pregnancy rates, and embryo implantation rates with increased SPA. Furthermore, there is a slight decrease in spontaneous abortions rates related to increased SPA.