Which sperm parameter limits could really guide the clinical decision in assisted reproduction?

Background The predictive role of sperm motility and morphology was recently detected in a large sample of more than 20000 assisted reproductive technology (ART) fresh cycles. However, the complete ART procedure consisted of both fresh and frozen-embryos transfers and only a comprehensive evaluation of the entire process could really confirm if these parameters really predict the ART success. The aim of the study was to evaluate which sperm parameter could predict the success of ART. Methods A retrospective, real-world data analysis was performed, enrolling all couples attending ART from 2008 to 2021, including both fresh and frozen cycles and both in vitro fertilization (IVF) and intra-cytoplasmic sperm injection (ICSI) procedures. Results Fresh cycles success (considering live birth rate) was predicted by female age (1.04 [1.02-1.06]), injected oocytes (0.96 [0.93-0.99]), embryo number (0.79 [0.75-0.83]) and progressive sperm motility (0.98 [0.97-0.99]). On the contrary, frozen cycle outcomes were predicted only by sperm motility (0.97 [0.95-0.99]). This prediction was confirmed in IVF but not in ICSI cycles. Conclusion Both female and male parameters predicted the ART success considering the entire path. However, frozen cycle success was predicted only by progressive sperm motility in IVF cycles, suggesting that the potential amelioration of this male parameter is relevant to improve ART success. Those couples expected to obtain the highest embryos after fertilization (low female age and better semen parameters) will have more attempts with frozen cycles and thus would benefit from a potential treatment focused to improve sperm parameters.