Sperm DNA fragmentation
There are different reasons that cause infertility, fragmentation in sperm DNA is one of the reason behind male infertility. It has a direct impact on the success rate of fertility treatment such as intrauterine insemination (IUI) and in-vitro fertilization (IVF). Through DNA Fragmentation Index (DFI), sperm quality can be accurately measured, once fertility treatment is required, doctors or embryologists can pick up sperm with normal DNA through a particular method to increase the success rate of treatment.
Causes of sperm DNA fragmentation:
- Age: Studies have shown that the quality and motility of sperm decrease with the increase of age.
- Smoking: Smoking is related to male infertility, smoking will reduce the number of sperm and semen volume, also cause damage to sperm DNA.
- Elevated testicular temperature: Researchers have found that when male’s testicules are in high temperature for a long period of time, the histones to protamine ratio in sperm may increase, causing sperm DNA fragmentation.
- Prostatitis: Inflammation at the prostate gland can lead to leukocytospermia, causing damage to sperm DNA.
- Chemotherapy: Cancer drugs are toxic to germ cells which are cells that will become sperm, causing damage to the DNA molecules and infertility.
- In contact with chemicals, toxic substances or exposed to radiation can also increase the risk of sperm DNA fragmentation.
Testing for sperm DNA fragmentation
Different methods can be used to measure the quality of sperm, for example, Comet and TUNEL can be used to detect single and double strand break in sperm DNA, SCSA test can examine chromatin structure and NT assay can identify single strands breakage in DNA.
What is a normal sperm DNA fragmentation rate?
According to sperm DNA Fragmentation Index (DFI), DFI less than 15% means good DNA integrity, DFI between 15% to 30% indicates sperm DNA integrity is moderate and sperm DNA integrity is poor if DFI is above 30%.
The impact of sperm DNA fragmentation on the success rate of fertility treatment
Intrauterine insemination (IUI)
- If DFI is less than 30%, the success rate of IUI can be up to 17.6%
- If DFI is higher than 30%, the success rate of IUI will be dropped to 4.5%
In-vitro Fertilization (IVF)
- Sperm DNA fragmentation has a direct impact on pregnancy rate and embryo development, even if embryo implantation is successful, the miscarriage rate is twice the normal embryo.
Does it mean there is no DNA fragmentation issue if everything is normal in semen analysis?
Even if everything is normal in semen analysis, it does not mean there is no DNA fragmentation problem as DNA fragmentation cannot be identify in regular semen analysis. Some patients still suffer from high DNA fragmentation rate and infertility even their semen analysis results are normal. These kind of infertility is classified as unexplained due to the limited medical knowledge in the past. However, thanks to the technology, more reasons can now be identified. This allows doctors to choose the most suitable treatments, such as infertility caused by sperm DNA fragmentation, and to prescribe medicine to improve DNA fragmentation problem.
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