Sperm selection by birefringence: a promising non-invasive tool to improve ICSI outcomes.

Despite higher sperm DNA fragmentation may affect intracytoplasmic sperm injection (ICSI) outcomes, sperm selection protocols do not evaluate this parameter. Therefore, sperm's head birefringence has been suggested as an adjuvant of seminal processing to select viable sperm for couples with severe male factor. Considering men with normal seminal parameters may also curse with DNA fragmentation, the aim of this study was to evaluate the impact of sperm selection by birefringence on ICSI outcomes in couples with different infertility factors compared to those submitted to conventional sperm selection. In this case-control study, medical records from 181 couples who underwent ICSI from January 2018 to August 2020 (107 from the Conventional and 74 from the Birefringence group) were included in the study. Clinical characteristics and ICSI outcomes were compared between the groups using Student's t test or Chi-square test (p<0.05) and a multivariate logistic regression model was applied regarding clinical pregnancy. Despite the Birefringence group showed higher female age (p=0.01), lower seminal sperm concentration (p<0.01) and higher sperm DNA fragmentation (p<0.01), those patients cursed with both higher cleavage rate (p=0.04), clinical pregnancy rate per transfer (p=0.03) and clinical pregnancy rate per initiated cycle (p=0.02). The logistic regression showed a positive group effect on clinical pregnancy. The findings suggest a positive clinical impact of this cheap and easily reproducible adjuvant technique on ICSI outcomes in couples with different infertility factors. If confirmed by further methodologically appropriate studies, the sperm's head birefringence could be considered to improve the reproductive chances of those patients.