Information about Sperm DNA Fragmentation for Clinicians

Almost 50% of all cases of infertility may be associated with a male factor. A semen analysis that measures sperm concentration, motility and morphology has classically been used as the gold standard test for determining a man’s fertility. However, this test does not provide any information about the genetic constitution of the sperm, which is essential for normal embryo development. Thus a high level of DNA damage in sperm cells may represent a cause of male infertility that conventional examinations cannot detect. Sperm DNA fragmentation is significantly higher in infertile men and while men with poor semen parameters are more likely to have high sperm DNA fragmentation, high sperm DNA fragmentation is also found in men with normal semen parameters who may be diagnosed with unexplained infertility1.

Sperm DNA and Embryo Development

Sperm with high DNA damage will contribute to nuclear instability in the embryo, resulting in arrested development, failed implantation and a higher miscarriage rate 2-4. High sperm DNA fragmentation is more likely to affect embryos from day two of development once the paternal genome is switched on. There is some evidence to suggest that DNA damage in the embryo could result in cell degeneration and gene mutations, leading to abnormalities in the offspring and an increased susceptibility to childhood cancers4,5


Sperm DNA, Pregnancy and Miscarriage

There is considerable evidence to show that the chances of a successful pregnancy are significantly reduced in couples where the male partner has a high percentage of sperm with fragmented DNA. Several large systematic reviews and meta-analyses have revealed that high sperm DNA fragmentation is associated with reduced pregnancy rates and live birth rates following natural or assisted conception, as well asan increased risk of miscarriage6-9. A recent systematic review and meta-analysis showed a significant elevation in sperm DNA fragmentation levels in partners of women experiencing recurrent pregnancy loss following spontaneous conception10. Overall the results of these studies lend support for the value of testing for sperm DNA fragmentation to identify possible causes for unexplained infertility, failed IVF treatment cycles or recurrent miscarriage3,11,12. Current European Society for Human Reproduction and Embryology (ESHRE 2017) guidelines recommend sperm DNA fragmentation testing for men whose partners experience recurrent pregnancy loss.


Causes of Sperm DNA Fragmentation

Sperm DNA fragmentation may arise as a result of defects in sperm chromatin packaging and DNA repair mechanisms as well as abnormalities in the regulation of programmed cell death (abortive apoptosis) which is vital for regulating sperm production3,13. A major causative factor for sperm DNA damage is oxidative stress due to excessive production of reactive oxygen species5,3,5,14,15. It is thought that oxidative stress contributes to single-strand DNA breaks which are associated with a delay to conception or no pregnancy, whereas double-strand DNA breaks are less common and are more likely due to an aberrant repair mechanism during meiosis16. This in turn results in poor embryo development, reduced implantation rates and a higher risk of miscarriage. Increased sperm DNA fragmentation is also associated with a variety of exogenous factors listed in the table below.



Factors Influencing Sperm
DNA Fragmentation3,5,14

  • infection
  • leucocytospermia
  • high fever
  • elevated testicular temperature
  • varicocoele
  • advanced age
  • obesity 
  • poor diet
  • drug use
  • cigarette smoking
  • exposure to environmental and occupational pollutants
  • increased length of sexual abstinence

Indications for Male Patients
Who May Benefit from a Sperm
DNA Fragmentation Test3,12

  • unexplained infertility
  • arrested embryo development
  • poor blastocyst development
  • multiple failed IVF/ICSI treatment
  • recurrent miscarriage in partner
  • advanced age 
  • varicocoele/varicocoelectomy
  • poor semen parameters
  • exposure to harmful substances

What is the DNA fragmentation test?

The test we offer is the sperm chromatin structure assay (SCSA®)11,17. This test is an effective method for measuring single and double stranded DNA breaks in thousands of sperm in an ejaculate. It measures the susceptibility of sperm DNA to denaturation when it is exposed to heat or acids. Sperm are stained with a fluorescent probe that interacts with the DNA molecule. The fluorescence signal changes when the DNA is fragmented, and this is monitored using a flow cytometer. The SCSA® test has been developed using human and animal models over the last 35 years and is one of the most statistically robust tests available for sperm DNA fragmentation. It is a standardised, validated CLIA approved test with high reproducibility and low variability11,17.

The Test Report 

The test reports two indicators of DNA damage:  


1. DNA Fragmentation Index (%DFI: % sperm cells containing damaged DNA)


Results are reported showing 4 statistical categories of fertility potential:


≤ 15% DFI = excellent to good sperm DNA integrity 

> 15 to < 25% DFI = good to fair sperm DNA integrity

> 25 to < 50% DFI = fair to poor sperm DNA integrity

≥ 50% DFI = very poor sperm DNA integrity


Note: The above values relate to natural and IUI conceptions. The statistically significant DFI threshold for subfertility has been established at > 25 %.


Normal full-term pregnancies are possible with an elevated DFI, but the higher the level of fragmentation, the greater the incidence of reduced term pregnancies and miscarriage. The above values relate to natural and IUI conceptions. When % DFI is above 25%, current literature suggests that the patient either try to reduce the DFI by medical intervention or change of lifestyle, or skipping IUI and go on to IVF ICSI for greatest success ( for details).


Hypothesis: A high ratio of moderate DFI to high DFI sperm may be the most negative since moderate DFI sperm have normal nuclear morphology and will likely fertilise but may have DNA damage beyond the repair capacity of eggs.

2. High DNA stainability (HDS): % sperm with immature chromatin and abnormal ratios of histones to protamines. Levels in the > 25% range are considered negative for pregnancy outcome


Treatment for Sperm DNA Fragmentation

One of the most simple ways to reduce sperm DNA damage is to encourage frequent ejaculation as this has been shown to significantly reduce sperm DNA damage and improve pregnancy outocmes3. Sperm DNA damage is associated with clinical varicocoele18 which is the leading known cause of male infertility. There is now growing evidence to show that clinical varicocoele repair may improve sperm DNA integrity18.Treatment of infection with antibiotics may also be beneficial in reducing sperm DNA damage19. DNA fragmentation may be caused by oxidative stress resulting from varicocele or infection. Alternatively, oxidative stress may arise from insufficient levels of seminal antioxidants. A change in lifestyle and a diet designed to protect against oxidative stress may help reduce the levels of DNA fragmentation in some of these cases3,11,14,20. Studies using antioxidant supplementation to reduce DNA damage are promising11,20. Men with oligozoospermia and elevated DNA damage may also benefit from treatment with FSH21. Initiatives to reduce the levels of DNA fragmentation can be assessed by undertaking a second test three months after the first.


Circumvention of Sperm DNA Damage

It is not always possible to repair sperm DNA damage particularly if the damage is due to abnormal chromatin packaging or abortive apoptosis. It has been proposed that DNA damage can occur at the post-testicular level, so that testicular sperm may have healthier DNA integrity than ejaculated sperm15. Systematic reviews of the literature reveal that use of testicular sperm rather than ejaculated sperm significantly increases pregnancy rates in cases where men have oligozoospermia and elevated sperm DNA fragmentation22 or in normozoospermic men with high DNA fragmentation23 and unexplained infertility. Several large studies show that ICSI may be a more effective treatment than IVF for sperm with high DNA fragmentation since its impact on fertilisation and pregnancy rates are not as detrimental compared to IVF7-9,24. IUI is not advised when sperm DNA fragmentation levels are high as pregnancy outcomes are very poor25.


Advantages of a Sperm DNA Fragmentation test

The test provides a reliable analysis of sperm DNA integrity that may help to identify men who are at risk of failing to initiate a healthy ongoing pregnancy. Information about sperm DNA integrity may help in the clinical diagnosis, management and treatment of male infertility and may be of prognostic value in assessing outcome of assisted conception treatment3,11,12.Identification of high levels of DNA fragmentation in the sperm may guide the clinician as to whether sperm donation may be appropriate. Sperm DNA fragmentation testing may help couples make an informed choice regarding their subsequent course of treatment.



Additional information downloads:

Sperm DNA Fragmentation, Aneuploidy & Epigenetics Test Request & GDPR Consent Form





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