About 100-300 million sperm are deposited in the vagina at the time of ejaculation during sexual intercourse. However, less than 25 actually reach the egg, and only one will penetrate and fuse with the egg. Sperm health is obviously vital, and it depends on quantity, quality and movement of the sperm.
For men who are fertile, 95 percent of them have a sperm density of at least 15 million per millilitre of semen (a normal semen sample has a volume of between 1.5 and 6 millilitres). Regarding quality, four percent or more of sperm should have a normal shape, or morphology (oval head and long tail). Related to movement, or motility, around 40 percent or more of those sperm should have forward movement at least one hour after ejaculation.
These figures are only a rough guide, and pregnancy can be achieved with lesser counts. One of the most important features is the total number of motile sperm in the ejaculate.
In many cases of male infertility, the cause can’t be identified. But men experiencing infertility should be aware of known causes that affect sperm health.
- Illness can affect sperm count. Something as simple as a sore throat for which you need treatment with antibiotics can significantly lower your sperm count. It takes about 70-74 days to produce new motile sperm so any illness during this timeframe can negatively affect sperm production.
- Smoking and drinking alcohol both have a negative effect on male fertility. Heavy cigarette smoking reduces both sperm count and motility. Excessive alcohol consumption lowers testosterone secretion, speeding up its chemical breakdown and conversion to estrogen. That can lower the sex drive. Alcohol also reduces sperm production.
- Some medications reduce sperm count. Salazopyrin (for colitis), phenytoin (epilepsy), colchicine (gout) and nitrofurantoin (urinary infections) may reduce sperm count. Alternate drugs are available for those maladies. Drugs used to treat certain cancers, such as cyclophosphamide, can cause permanent infertility if used in large doses. Testosterone taken to build muscle mass may irreversibly reduce sperm count.
- Virtually all street drugs impair sperm production. For example, morphine and heroin cause infertility and impotence by stimulating the release of the hormone prolactin. Marijuana has been found to cause infertility, probably by lowering the hormones FSH and LH.
- Abnormal sperm production may be caused by hormonal problems, such as undescended testicles and injury or damage to testicles from infections, chemicals or drugs. However, hormonal causes of infertility in men are unusual.
- Stress, often a byproduct of infertility, can interfere with the hormones that produce sperm.
Studies into sperm health are increasing and turning up possible new connections. For example, research indicates that obesity negatively affects sperm count and motility. Environmental pollution has been identified as a possible factor in reduced sperm quality. Researchers have found a correlation between a sedentary lifestyle and lower sperm counts. Studies have suggested a link between high-activity bicycling and reduced sperm concentration, possibly due to the stress the seat puts on the scrotum.
Couples experiencing infertility should consult with their physician so they can be aware of all possibilities that can affect their outcome, including the sperm health of the male.