Double-stranded sperm DNA fragmentation measured with neutral comet assay as a predictor of IVF outcomes: evidence from three European clinics in a multi-centred prospective study.

study questionCan measurement of double-stranded sperm DNA fragmentation (dsSDF) via a neutral comet assay predict the probability of live birth following IVF? SUMMARY ANSWER: In a multicentre IVF cohort, dsSDF measured by a neutral comet assay was a strong, independent predictor of live birth. WHAT IS KNOWN ALREADY: While much of the focus has traditionally been on female factors, emerging research highlights sperm DNA fragmentation as a significant contributor to reproductive outcomes. Over the past decade, studies have shown that different types of sperm DNA damage can affect reproduction differently, with single-stranded breaks being closely linked to reduced spontaneous conception rates, while double-stranded breaks are linked to higher miscarriage rates. STUDY DESIGN, SIZE, DURATION: Prospective cohort study including a total of 302 males from three European IVF clinics, over a 3-year study period (March 2021-October 2024), with 126 healthy sperm donors with confirmed live birth serving as controls. PARTICIPANTS/MATERIALS, SETTING,

methodsdsSDF was quantified with a neutral comet assay, expressed as Average Comet Score (ACS) and Incidence of Damage (IOD). The primary outcome was live birth per initiated cycle. Associations were evaluated using multivariable logistic regression, adjusting for female and male age (and centre in sensitivity analyses). MAIN RESULTS AND THE ROLE OF CHANCE: Across the cohort, 30% of couples achieved a live birth. Higher dsSDF was associated with reduced odds of live birth, and this association remained statistically significant after adjustment for female age, male age, and recruitment site. Both ACS and IOD were independently predictive of live birth in adjusted models. For ACS, each 1-point increase was associated with 16% lower odds of live birth (OR = 0.84, 95% CI 0.72-0.97; P = 0.026). For IOD, each 1-point increase corresponded to 5% lower odds of live birth (OR = 0.95, 95% CI 0.90-0.99; P = 0.025). As expected, female age remained a strong inverse predictor of live birth across models (OR = 0.86, 95% CI 0.78-0.94; P < 0.001). Using a pragmatic threshold of IOD ≥ 6%, couples were identified with approximately half the odds of achieving a live birth compared to those with IOD < 6% at similar female ages (OR = 0.51, 95% CI 0.28-0.94; P = 0.029). The adverse association between dsSDF and live birth was stronger at higher female ages. LIMITATIONS, REASONS FOR CAUTION: This study examined couples undergoing their first or only IVF cycle and did not include couples with repeat IVF failures. Limitations include potential centre-level confounding, which may benefit from mixed-effects modelling. We did not collect or adjust for several cycle-level covariates that influence live birth (e.g. IVF vs ICSI, number of oocytes retrieved, embryo transfer strategy, use of preimplantation genetic testing for aneuploidy, stimulation protocol), so residual confounding is possible. WIDER IMPLICATIONS OF THE

findingsThese results support dsSDF as a clinically relevant biomarker that complements conventional semen parameters. STUDY FUNDING/COMPETING INTEREST(S): The study was part-funded using an unrestricted medical educational grant provided by Merck Serono Limited (0111897641) to the Liverpool Women's Hospital. T.C.B.M., S.H.M., and E.B. were funded in part by UKRI SIP FMI and Peace Plus HF-TIC grants with Ulster University. L.R., A.S., M.L., C.J.L., L.P., and T.C.B.M. are employed at Examen Lab LTD. A.J.D. is a recipient of Merck Serono Limited (0111897641) grant to the Liverpool Women's Hospital. P.H. has received unrestricted research grants from Merck and Gedeon Richter Nordics and honoraria for lectures from Merck, Gedeon Richter, and IBSA. The remaining authors have nothing to disclose. TRIAL REGISTRATION NUMBER: N/A.