Researchers review the evidence for sperm DNA fragmentation testing

A 2025 review found that sperm DNA fragmentation testing provides useful insight into male infertility and may help in select cases, but inconsistent evidence, lack of test standardization, and variable results limit its routine use in fertility care.

Sperm DNA fragmentation (SDF) refers to breaks or damage in the DNA of sperm. Even when sperm counts, motility, and morphology appear normal, fragmented DNA can reduce fertilization, embryo development, and pregnancy success.

SDF can be caused by problems during sperm production, such as faulty DNA packaging or failed cell repair, or by environmental factors like excessive heat, smoking, or infection. High SDF levels are more common in men with varicocele, advanced age, hormonal or metabolic issues, environmental exposure, or poor lifestyle factors such as obesity, smoking, or prolonged abstinence.

A variety of tests can be used to evaluate SDF levels, including TUNEL, SCSA, SCD, and Comet, which represent popular IVF add-ons.

Although high SDF is linked to poorer fertilization, embryo quality, and pregnancy outcomes, evidence is mixed and routine testing is controversial. Llácer et al. (2025) reviewed 174 articles on SDF and applied a SWOT analysis, a framework that looks at Strengths, Weaknesses, Opportunities, and Threats, to evaluate how well SDF testing works in fertility care and where more research is needed. This post will summarize their findings as it relates to the strengths and weakness of SDF testing, linking to some of the stronger studies that support their claims.

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Strengths: Evidence supporting the use of sperm DNA fragmentation testing

These are the main scientific and clinical reasons why sperm DNA fragmentation is considered important and worth studying, testing, and addressing in fertility care.

• Biological plausibility and mechanisms: There’s a strong biological foundation for SDF: sperm DNA can be damaged by poor packaging, failed cell cleanup, or oxidative stress, which can lead to poorer embryo development or implantation potential.
• Impact on natural fertility: In couples trying naturally, higher SDF is linked to lower conception rates, including a 7-fold decrease in one meta-analysis (Zini 2011). Another study showed that infertile men have higher DNA fragmentation than fertile men.
• Links with aneuploidy and embryo quality: Damaged sperm DNA has been tied to chromosomal abnormalities and poorer embryo quality, especially in older men, although evidence is mixed. This suggests the effects of SDF can extend into embryo development.
• Effect on fertilization: The largest meta-analysis on this topic found that men with high sperm DNA fragmentation had lower fertilization rates when tested with the SCD method (Kaiyal et al. 2024). A smaller meta-analysis (Chen et al. 2022) found no significant effect of SDF on fertilization, suggesting that the impact of SDF on fertilization rates remains uncertain.
• Pregnancy rates: Studies show that when SDF is high, pregnancy rates are lower with IUI (Chen et al. 2019), where sperm must reach and fertilize the egg on their own. In IVF, high SDF is also linked to lower pregnancy rates in several large meta-analyses (Simon et al. 2017), though the effect is smaller than IUI, while studies with ICSI may show smaller differences or no difference at all (Ribas-Maynou et al. 2021). This difference may be explained by the “two-step hypothesis,” which suggests that sperm with higher DNA fragmentation are more fragile and can incur additional damage as they travel toward the egg. Because IVF shortens this journey and ICSI bypasses it entirely, less damage may occur, leading to better outcomes. Some authors have also noted that ICSI studies often involve younger female patients, whose eggs may be better at repairing sperm DNA damage and could help explain why SDF seems to matter less in these cases.
• Miscarriage and recurrent pregnancy loss (RPL): Meta-analyses have shown that miscarriage risk can be higher with increased SDF (Zhao et al. 2014), while others have shown no effect (Kaiyal et al. 2024). A recent umbrella review by Zhang et al. (2024) combined the results of 7 meta-analyses, ranking high SDF as having “highly suggestive evidence” for an association between SDF and RPL.
• Modifiable risk and treatment potential: Studies suggest that high SDF may be reversible, as treatments such as varicocele repair, antioxidant therapy, and lifestyle improvements may lower DNA damage and improve fertility outcomes, although results are mixed (Esteves et al. 2020).

Weaknesses: Limitations of sperm DNA fragmentation testing

These are the main limitations and uncertainties that make SDF testing less reliable or harder to use consistently in clinical care.

• Complex and multifactorial causes: DNA damage can result from many different factors, and each SDF test may capture these in different ways. Not every case of high SDF improves with treatment, possibly because the underlying causes and types of DNA damage vary, making results harder to interpret.
• Different types of DNA damage: Different types of sperm DNA damage may have different effects on fertility. Double-strand breaks are linked to poorer embryo development, lower implantation rates, and recurrent pregnancy loss, while single-strand breaks may have less effect on IVF outcomes but are associated with lower chances of natural conception. Most SDF tests can’t tell these types of SDF apart.
• No gold-standard test: Different SDF tests vary in complexity and purpose — TUNEL detects damage directly, SCSA is highly reproducible but mainly used in clinical studies, SCD is simple and commonly used for patient diagnostics, and Comet provides detailed analysis but is mainly used in research. All have limited predictive power for IVF outcomes and can give inconsistent results between studies and labs due to differences in protocols and how samples are prepared (Cissen et al. 2016).
• Variability in results: SDF results can vary widely between samples and laboratories — one study showed changes in SDF levels over six weeks in the same individuals (Smit et al. 2007). Differences in sperm handling, timing, freezing, and lab techniques have all been shown to introduce variability in SDF tests, making the tests less consistent and harder to use reliably in routine clinical care.
• Unclear thresholds: A major limitation of SDF testing is the lack of a standardized cut-off for what counts as “high” DNA fragmentation. Different studies use different thresholds because results vary depending on the testing method, patient population, and type of fertility treatment.
• Influence of female factors: The effect of SDF depends partly on the woman’s age and egg quality, since healthy oocytes can repair some sperm DNA damage. Younger or higher-quality eggs can often overcome moderate SDF, but not all types of DNA breaks are repairable, making test results harder to interpret and less consistent across patients.
• Inconsistent link to live birth: Large studies and meta-analyses have produced mixed results on whether SDF affects live birth rates. Some studies suggests that higher SDF is linked to lower live birth rate, but most large analyses found no significant relationship (eg. Ribas-Maynou et al. 2021). One study found lower cumulative live birth rates in men with high SDF, particularly when the female partner was older (Qu et al. 2024).
• Limited good quality evidence: Most studies on SDF are observational and lower quality, and affected by differences in patient characteristics, lab methods, and study design, making it difficult to determine the true impact of SDF on fertility results.

Conclusions

SDF testing offers valuable insight into sperm health and provides information that routine semen analysis can’t.

Studies show that high SDF is linked to lower chances of natural conception and IUI success, poorer fertilization, reduced pregnancy rates, and a higher risk of miscarriage. Studies suggest that high SDF may be reversible, as treatments such as varicocele repair, antioxidant therapy, and lifestyle improvements may lower DNA damage and improve fertility outcomes.

However, results across studies can be mixed, with some showing no effect. Other weaknesses include the lack of a standard test or clear threshold for what counts as “high” SDF, variability between samples and laboratories, and no consistent link to live birth rates. Outcomes also depend on the woman’s age and egg quality, and most studies so far are low quality, making it difficult to draw firm conclusions.

Overall, the authors note that SDF testing can be helpful for couples with unexplained infertility, recurrent miscarriage, or repeated IVF failure. They emphasize the need for standardized testing methods, clear thresholds, and high-quality randomized trials to better define its role in IVF. “Until then, SDF testing should be considered a second-line diagnostic tool — useful in selected cases, not as a universal screening test,” the authors write.

Want to read more about sperm DNA fragmentation and the evidence behind popular IVF add-ons?

Reference

Spanish Infertility SWOT Group (SISG); Llácer J, Requena A, Checa MÁ, Bellver J, Bosch E, Espinós JJ, Fábregues F, Ortega AI, Fontes J, García-Velasco JA. The role of sperm DNA fragmentation in reproduction: a SWOT analysis. J Assist Reprod Genet. 2025 Sep 27. doi: 10.1007/s10815-025-03645-9. Epub ahead of print. PMID: 41015643.

 

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About Embryoman

Embryoman (Sean Lauber) is a former embryologist and the founder of Remembryo, an IVF research and fertility education website. After working in an IVF lab in the US, he returned to Canada and now focuses on making fertility research more accessible. He holds a Master’s in Immunology and launched Remembryo in 2018 to help patients and professionals make sense of IVF research. Sean shares weekly study updates on Facebook, Instagram, and Reddit regularly. He also answers questions on Reddit or in his private Facebook group.

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