Association Between Sperm DNA Fragmentation Index and Outcomes of Fresh Embryo Transfer in IVF/ICSI Cycles: A Retrospective Cohort Study

OBJECTIVE: This study explored the impact of the sperm DNA fragmentation index (DFI) on clinical outcomes and infant safety in in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) among infertile couples. METHODS: A retrospective cohort study analyzed clinical data from 4520 infertile couples undergoing fresh embryo transfer in IVF/ICSI cycles at Fujian Maternity and Child Health Hospital between June 2018 and January 2025. Participants were stratified according to BMI categories. The primary outcomes were semen parameters, while secondary outcomes included embryo-related, pregnancy, and fetal outcomes. Associations between sperm DFI and reproductive outcomes were evaluated using multivariable linear and logistic regression models. Restricted cubic spline models were applied to explore potential nonlinear relationships. Subgroup analyses were performed according to fertilization method (IVF or ICSI), and sensitivity analyses were conducted by modeling DFI as a continuous variable and by applying an alternative DFI cutoff value of 20%. RESULTS: Elevated sperm DFI was significantly associated with impaired semen quality across BMI strata. Compared with men with DFI <15%, those with DFI ≥15% exhibited lower sperm concentration, total sperm count, sperm motility, and normal morphology rate, with the strongest associations observed among men with high BMI. Regarding embryo-related outcomes, elevated DFI was associated with a lower fertilization rate among men with high BMI, whereas in the low-BMI subgroup, elevated DFI was associated with a higher high-quality embryo rate (Adjusted β = 10.24, 95% CI: 0.78 to 19.70). In the primary analyses, no significant associations were observed between sperm DFI and blastocyst formation, clinical pregnancy, abortion, live birth, fetal aneuploidy, or birth defects. Sensitivity analyses using DFI as a continuous variable and an alternative cutoff value of 20% yielded results generally consistent with the primary analyses. Subgroup analyses stratified by fertilization method demonstrated comparable associations between sperm DFI and reproductive outcomes, supporting the robustness of the findings. CONCLUSION: Sperm DFI is significantly associated with the quality of semen and embryo development in assisted reproduction. A positive association with high-quality embryo rate was observed in the low-BMI subgroup; however, this finding should be interpreted cautiously because of the relatively small sample size in the low BMI subgroup.