Semen quality is a measure of the ability of semen to accomplish fertilisation. Thus, it is a measure of fertility in a man. It is the sperm in the semen that are of importance, and therefore semen quality involves both sperm quantity and sperm quality.
A semen analysis typically measures the number of sperm per milliliter of ejaculate, and analyzes the morphology (shape) and motility (ability to swim forward) of the sperm. Also usually measured are the concentration of white blood cells, the level of fructose in the semen, and the volume, pH, and liquefaction time of the ejaculate.
A number of factors may influence the accuracy of semen analysis results, and results for a single man may have a large amount of natural variation over time. For this reason, a subfertile result must be confirmed with at least two further analysis.
A man's sperm are mixed with hamster eggs that have had the zona pellucida (outer membranes) removed, and the number of sperm penetrations per egg is measured. The human sperm does not fertilize the hamster eggs. A negative result on the hamster test correlates with a lower probability of the man's partner becoming pregnant.
Sperm chromatin assay
Chromatin is the complex of DNA and protein that make up chromosomes. If a large percentage of a man's sperm (greater than 30%) have damaged chromatin, his chances of impregnating a partner are significantly reduced, and if he does impregnate his partner, she faces an increased risk of miscarriage. The portion of a man's sperm with damaged chromatin may be determined with a Sperm Chromatin Structure Assay (SCSA).
When performing cryopreservation of semen, it is the sperm quality after reviving the sample that is of importance, because many sperm cells die in the process.
To be of use in assisted reproductive technology, the sample should after thawing have more than 5 million motile sperm cells per ml with a good grade of motility. If the grade of motility is poor, 10 million motile cells per ml is required.
In 10-20% of all men, the semen doesn't endure cryopreservation. The cause is unknown.
There are many factors that influence the sperm quality. If exposure to any of them has happened, it might take up to 3 months before the sperm quality is up to normal again, because that's how long time spermiogenesis takes.
Semen is heat-sensitive, and cannot endure too high temperatures. The body has compensatory mechanisms, like the cremaster muscle relaxing and letting the testicle further away from the warm body, sweating and a Countercurrent exchange of blood cooling inflowing blood. However, despite the compensation of the body, there are activities that should not be performed too often, in order of preventing infertility due to heat;
- sauna sessions
- bathing long time in hot water
- Long-time tanning bed sessions
- Tight and airtight trousers and underwear, since it hampers the sweating mechanism.
Fever also raises the body temperature, which can strike sperm quality.
In the same way, sperm quality can be lower in the summer.
A blow from outside doesn't affect the sperm quality of already produced sperm cells. Furthermore, the testes are well protected in the scrotum, for example by the tunica vaginalis, making the testes slide away from external pressure rather than being malformed from it.
There is suspicion that many toxic substances in the environment influence sperm quality. Exactly what chemicals are unknown, however. Sometimes it is claimed smoking marijuana lowers sperm count but this has never been proven.
The body also has natural variations in hormone concentrations, giving sperm quality natural fluctuations as well.
How long the man has abstained prior to providing a semen sample correlates with the results of semen analysis and also with success rates in assisted reproductive technology (ART). Longer periods of abstinence correlate with poorer results - one study found that men with repeated normal results from semen analysis produced abnormal samples if they abstained for more than 10 days. Another study found that couples where the man had abstained for more than 10 days before an intrauterine insemination (IUI) had only a 3% pregnancy rate.
For semen that has been ejaculated, the quality deteriorates with time. However, this lifetime can be shortened or prolonged, depending on the environment.
Sperm outside of the body generally has a life expectancy which is considered to depend on pH, temperature, presence of air and other factors, and is unpredictable but smaller than the life expectancy inside the human body. For instance, sperm donors who collect the sample outside the clinic are adviced to have handed in the sample before one hour from collection, and to keep them in, if not at body temperature, then at least at room temperature.
Lack of exercise, as well as excessive exercise, are minor factors.
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