Correlations Between Sperm DNA Fragmentation Index, Semen Parameters, and In Vitro Fertilization Embryo Culture Outcomes: A Single-Center Retrospective Study

Background: Sperm DNA fragmentation index (DFI) has emerged as a critical factor affecting male fertility, while the associations between DFI, conventional semen parameters and in vitro fertilization (IVF) embryo culture outcomes remain inconsistent in clinical studies. To investigate the impact of sperm DFI on embryo culture parameters in IVF treatment cycles. Methods: A comprehensive retrospective analysis was conducted on couples undergoing IVF treatment at the Reproductive Medicine Center of Wenzhou People’s Hospital between January 2019 and April 2024. Correlation and regression analyses were performed to evaluate the associations between sperm DFI and male partner characteristics, including age, semen volume, sperm concentration, total motility, and progressive motility. Based on established clinical thresholds, sperm nuclear DNA integrity was categorized as optimal (DFI ≤15%), moderate (15% < DFI < 30%), or compromised (DFI ≥30%). To control for confounding variables, propensity score matching (PSM) was performed twice, using DFI cutoffs of 15% and 30, respectively. Following PSM, the first matched cohort comprised 36 couples in Group A (DFI ≤30%) and 36 couples in Group B (DFI >30%). The second matched cohort comprised 265 couples in the normal group (DFI ≤15%) and 135 couples in the abnormal group (DFI >15%). Differences in fertilization rate, cleavage rate, high-quality embryo rate, usable embryo rate, and blastocyst formation rate between the two groups were compared using the chi-square test. Results: Correlation and regression analyses revealed a significant positive correlation between sperm DFI and male age (r = 0.244, p < 0.001) and significant negative correlations with total motility and progressive motility (r = –0.290, p < 0.001; r = –0.272, p < 0.001). No significant correlation was found between DFI and semen volume or sperm concentration. The fertilization rate in Group B (60.48%) was significantly lower compared to Group A (66.93%) (p < 0.05). Additionally, the fertilization rate in the abnormal group (64.69%) was significantly lower compared to the normal group (68.35%) (p < 0.05). There were no statistically significant differences in cleavage rate (96.93% vs. 97.62%; 97.58% vs. 98.15%), high-quality embryo rate (38.60% vs. 44.64%; 35.46% vs. 35.63%), usable embryo rate (68.42% vs. 67.86%; 65.69% vs. 62.01%), and blastocyst formation rate (59.38% vs. 60.66%; 60.63% vs. 62.32%) (all p > 0.05) between Group B and Group A, as well as between the abnormal group and the normal group. Conclusions: Sperm DFI was positively correlated with male age and negatively correlated with sperm motility, but showed no association with other semen parameters. Elevated sperm DFI was associated with reduced fertilization rates in IVF cycles. In contrast, subsequent embryonic development parameters were unaffected by DFI levels, suggesting that sperm DNA damage primarily affects early fertilization events rather than later embryonic development stages.