Semen quality does not depend solely on sperm count, motility or morphology. Some men, even those with semen analysis results within normal parameters, may have alterations in the genetic material of their sperm known as sperm DNA fragmentation.
This can affect different stages of the reproductive process, from fertilisation to embryo development and implantation, and may also be associated with an increased risk of miscarriage.
For this reason, sperm DNA fragmentation testing can provide additional information about sperm quality in certain cases of male infertility or when there is a history of reproductive failure.
What is sperm DNA fragmentation?
Sperm DNA fragmentation occurs when there are breaks or damage to the DNA strands within sperm cells.
These breaks can be divided into two main types:
- Single-strand breaks: affect one strand of the DNA. In certain circumstances, the oocyte may be able to repair some of this damage.
- Double-strand breaks: affect both strands of the DNA and are more difficult to repair. This type of damage may be associated with a poorer reproductive prognosis.
The integrity of sperm DNA is important because it contains the paternal genetic information that will contribute to the development of the future embryo.
What causes sperm DNA fragmentation?
One of the main factors associated with sperm DNA fragmentation is oxidative stress, an imbalance between the production of reactive oxygen species and the body’s ability to neutralise them.
Several factors can contribute to this type of damage.
Intratesticular factors
Within the testicles, fragmentation may be associated with:
- Alterations in chromatin compaction.
- Abnormal processes during sperm formation and maturation.
- Survival of sperm cells with a higher degree of genetic damage.
Extratesticular and lifestyle-related factors
Damage to sperm DNA can also occur during transit through the epididymis and seminal ducts.
Factors that may contribute include:
- smoking,
- obesity,
- varicocele,
- certain infections,
- exposure to pollution, toxins or radiation,
- unhealthy lifestyle habits,
- oxidative stress,
- and advanced paternal age.
The woman’s age may also be relevant in this context, as the oocyte’s ability to repair certain types of sperm DNA damage may decrease with age.
How can sperm DNA fragmentation affect fertility?
High levels of sperm DNA fragmentation may affect different stages of the reproductive process.
Possible consequences include:
- impaired fertilisation,
- poorer embryo development,
- reduced implantation potential,
- unsuccessful assisted reproduction treatments,
- and an increased risk of miscarriage.
Its impact is not the same for every patient. For this reason, the result of a sperm DNA fragmentation test should always be interpreted alongside the rest of the male and female fertility assessment.
When is sperm DNA fragmentation testing recommended?
Sperm DNA fragmentation testing is not routinely recommended for every man undergoing a fertility assessment.
However, it may provide useful information in certain circumstances, particularly in cases of:
- unexplained infertility,
- recurrent miscarriage,
- repeated IVF or ICSI failure,
- varicocele,
- advanced paternal age,
- poor embryo quality,
- or a medical history suggesting increased oxidative stress.
Whether the test is appropriate should be assessed individually according to each patient’s medical and reproductive history.
How is sperm DNA fragmentation tested?
Different tests are available to assess the integrity of sperm DNA. Some of the most commonly used include:
TUNEL test
This test detects breaks in sperm DNA by labelling the ends of fragmented DNA strands.
SCSA test
The Sperm Chromatin Structure Assay assesses the susceptibility of sperm DNA to denaturation and provides an index related to the level of DNA fragmentation.
SCD or Halosperm test
The Sperm Chromatin Dispersion test analyses chromatin dispersion patterns to identify sperm cells with fragmented DNA.
Comet assay
The Comet assay can be used to assess DNA damage and provide information about single- and double-strand DNA breaks.
Results and reference values can vary depending on the technique used and the laboratory, so they should not be interpreted in isolation.
As a general guide, some methods consider values below 20% to be associated with a more favourable scenario, while values above 30% may be associated with a poorer reproductive prognosis. However, these thresholds should always be interpreted according to the technique used and the patient’s individual clinical circumstances.
Can sperm DNA fragmentation be reduced?
In some patients, sperm DNA fragmentation can be reduced by addressing the factors that may be contributing to it.
The approach will depend on the individual case and may include:
- stopping smoking,
- improving diet and lifestyle,
- achieving a healthy weight,
- reducing exposure to certain toxins and pollutants,
- treating infections,
- treating varicocele when clinically indicated,
- reducing oxidative stress,
- and adjusting periods of sexual abstinence.
Antioxidants may also be considered in selected patients, although their use should be individualised and the evidence regarding their benefits remains variable.
What happens if sperm DNA fragmentation remains high?
When sperm DNA fragmentation remains elevated, particularly in patients who have experienced previous assisted reproduction failures, other strategies may be considered.
One option is the use of advanced sperm selection techniques to try to select sperm with more favourable characteristics.
These include microfluidic sperm selection systems, which are designed to facilitate the selection of motile sperm with characteristics associated with lower levels of DNA fragmentation.
In selected cases, specialists may also consider using sperm retrieved directly from the testicle for ICSI (Testi-ICSI), as testicular sperm may show lower levels of DNA damage in some patients.
These approaches are not necessary for every patient and should always be considered on an individual basis by a fertility specialist.
Sperm DNA fragmentation and male reproductive health
Male fertility assessment has evolved and, when clinically appropriate, can now go beyond conventional semen analysis.
Semen analysis remains a fundamental test, but it does not provide direct information about the genetic integrity of sperm.
For this reason, in selected patients, sperm DNA fragmentation testing can help specialists better understand certain cases of infertility, recurrent miscarriage, poor embryo development or previous assisted reproduction failures.
There is also growing interest in the possible relationship between sperm genetic integrity and the future health of offspring, although research in this area is still developing.
What should you do if sperm DNA fragmentation is high?
A high result should not be interpreted in isolation and does not necessarily mean that achieving a pregnancy is impossible.
The important step is to identify what may be causing the sperm DNA damage, assess male and female factors together, and determine whether lifestyle changes, treatment of an underlying cause or adaptations to an assisted reproduction treatment may be appropriate.
At Clínica Fertia, we carry out an individual assessment of male infertility, particularly when there is a history of recurrent miscarriage, implantation failure or previous unsuccessful fertility treatments.
Our aim is to determine which investigations are genuinely indicated and establish the most appropriate reproductive strategy for each individual case.
Would you like us to assess your case?
Book a consultation with our fertility specialists to discuss your situation and the most appropriate next steps.
References
- Marinaro JA, Schlegel PN. Sperm DNA Damage and Its Relevance in Fertility Treatment: A Review of Recent Literature and Current Practice Guidelines. Int J Mol Sci. 2023;24(2):1446.
- Esteves SC, Zini A, Coward RM, et al. Sperm DNA fragmentation testing: Summary evidence and clinical practice recommendations. Andrologia. 2021;53(2):e13874.
- Andrabi SW, Ara A, Saharan A, et al. Sperm DNA Fragmentation: causes, evaluation and management in male infertility. JBRA Assist Reprod. 2024;28(2):306-319.
Published: 17 January 2025 · Last updated: 2 September 2026
