Semen quality
Exposure to any of the temporary factors can cause up to a three-month delay before sperm quality returns to normal, due to spermiogenesis.
However, despite these compensations, some activities should not be performed too often, to prevent infertility due to heat: Fever raises the body temperature, which can affect sperm quality.
Contrary to widely held beliefs, no evidence supports that wearing tight underpants decreases fertility.
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; however, a hard enough hit can close or crush the capillaries that supply the sperm-producing tissue, resulting in permanent or temporary and partial or total inability to produce sperm in the affected testicle.
There is suspicion that many toxic substances, including several types of medication and hormones, and also constituents of the diet, influence sperm quality.
Many products that come into direct contact with spermatozoa lack adequate testing for any adverse effect on semen quality.
[9] At least three types of synthetic toxins have been found in the semen of student volunteers: polychlorinated biphenyls (PCBs), DDT, and hexachlorobenzene.
[10] Soldiers that were exposed to dioxins and dioxin-like compounds during the Vietnam war have given rise to children with an increased rate of birth defects.
[10] Phthalates, a ubiquitous pollutant, may cause decreased sperm production when having been exposed to it during prenatal development.
[8] In addition, in vitro studies have observed altered sperm function by the following medications: Also, numerous products intended for exposure to spermatozoa have only a general assumption of safety based on the absence of evidence of actual harm.
[26] Longer periods of abstinence correlate with poorer results—one 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.
[36] In a non-harmful environment outside the body, such as in a sterile glass container[31] the number of motile sperm decreases by approximately 5–10%[31] per hour.
In contrast, in a latex condom, the quality decreases by 60–80%[31] per hour, rendering the sample unusable in a relatively short time.
[37][38][39] Tobacco smoking lowers sperm quality,[10] perhaps by decreased ability to attach to hyaluronan on the egg cell.
[40] Wright et al.[6] have reviewed evidence that smoking is associated with increased sperm DNA damage and male infertility.
In professional sports, semen quality parameters tend to decrease as training requirements increase.
[46] Males carrying Robertsonian translocations in their chromosomes have significantly higher degree of sperm cell apoptosis and lower concentration.
[48] A semen analysis typically measures the number of sperm per millilitre of ejaculate and analyzes the morphology (shape) and motility (ability to swim forward) of the sperm (the typical ejaculate of a healthy, physically mature young adult male of reproductive age with no fertility-related problems usually contains 300–500 million spermatozoa, though only a couple of hundred survive in the acidic environment of the vagina to be candidates for successful fertilization).
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.
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 mobility.
