Sperm DNA Fragmentation in Normozoospermic Men Is Associated with Blastocyst Formation and Quality in Conventional In Vitro Fertilization

Background: Assisted reproductive therapy (ART) has been utilized as an effective therapeutic strategy for addressing infertility worldwide, and one of the key determinants of ART success is the acquisition of high-quality embryos through in vitro fertilization (IVF). We investigated here which male factors were associated with embryo formation and quality in conventional IVF (cIVF). Methods: This study was an exploratory sub-analysis of a trial conducted to examine the associations of clinical and lifestyle factors with sperm abnormalities in 41 men of infertile couples without identifiable male factors. From the original cohort, 21 men whose partners underwent cIVF were included for blastocyte outcome assessment. Semen samples were evaluated for standard sperm parameters and DNA fragmentation index (DFI). Blood biochemical parameters and lifestyle habits were also evaluated. Blastocysts were assessed 5 days after cIVF, and implantation success was determined 10 days after embryo transfer. Results: All participants showed normozoospermia with mild sperm DFI in 76%. Blastocysts were formed in 32% of the oocytes following cIVF, with good blastocyst development and quality observed in 71% and 39%, respectively. The implantation success and live birth rates after embryo transfer was 53% and 43%, respectively. Regression analysis identified sperm DFI as the only variable inversely associated with all blastocyst outcomes. In contrast, no parameters were associated with implantation success or live birth rates. Conclusions: The present findings suggest the hypothesis that sperm DNA fragmentation may negatively affect high-quality embryo formation in cIVF, even among normozoospermic men with non-severe levels of sperm DFI.