American Medical Association Family Medical Guide - American Medical Association [264]
• Medical conditions Some disorders, such as diabetes (see page 889) or hypothyroidism (see page 903), can inhibit ovulation and the production of the hormones needed to sustain a pregnancy.
• Scant or thick cervical mucus Mucus secreted by the cervix normally eases the passage of sperm, but in rare cases in which the amount of mucus is either insufficient or the mucus is too thick, sperm cannot enter the uterus.
Causes of Infertility in Men
Most causes of infertility in men result from the inability of sperm to fertilize an egg. A man may not produce enough sperm, the sperm may not be mobile enough to reach an egg and fertilize it, or the sperm may be abnormal in shape or size. Blockage of the vas deferens (one of the tubes that carry sperm from the testicles to the urethra) also can prevent sperm from leaving the body during ejaculation. Erection problems (see page 486) have a similar effect. The most common causes of male infertility include:
• Chronic infection Some STDs, such as chlamydia (see page 477) and gonorrhea (see page 480), and other infections (such as an infection in the prostate gland) can produce a blockage in the vas deferens or lower the number of sperm produced (sperm count).
• Exposing the testicles to high temperatures The testicles are outside of the body, in the scrotum, because they need to be in a temperature lower than body temperature to work properly. Soaking for a long time in a tub of very hot water, wearing tight clothing, or sitting for long periods can raise the temperature of the testicles, reducing sperm count.
• Cigarettes, alcohol, and drugs Smoking more than a pack of cigarettes a day, drinking excessively, or using marijuana or cocaine can lower sperm count and reduce sperm motility (movement).
• Varicose veins in the testicles Called varicoceles (see page 829), varicose veins in the testicles decrease sperm production and affect about 40 percent of infertile men.
• Reproductive tract surgery Hernia repair, prostate surgery, or a vasectomy can produce scar tissue or damage nerves, affecting the functioning of the vas deferens and obstructing the flow of semen.
Abnormal sperm
All men have some abnormal sperm that cannot fertilize an egg. Abnormal sperm can be too small, too large, or misshapen. A man is considered fertile if at least half of his sperm are healthy. (All illustrations are magnified.)
• Prescription drugs Medications used to treat depression or high blood pressure can make it difficult to achieve an erection.
• Medical conditions Some disorders—such as diabetes (see page 889), heart disease (see page 558), multiple sclerosis (see page 696), and Parkinson’s disease (see page 691)—can affect blood vessels and nerves and cause erection problems.
• Structural abnormalities in the reproductive tract Structural abnormalities, which may be congenital (present at birth) or develop from infection or surgery, can obstruct the passage of sperm or semen.
• Injury to the groin An injury to the testicles can produce scar tissue that obstructs the passage of sperm.
• Disorders of the immune system Conditions that affect the immune system, which may be hormonal or may occur when a man’s immune system mistakenly produces infection-fighting antibodies that attack his own sperm, can prevent sperm from reaching and penetrating an egg.
• Ejaculation problems If a man has erection problems or a condition in which semen is ejaculated backward into the bladder (called retrograde ejaculation), sperm cannot fertilize an egg.
Lifestyle Factors That Affect Fertility
The causes of infertility are numerous, and many can be traced to a treatable medical condition, but some lifestyle factors also can affect your chances of conceiving a child. If you are trying to conceive, keep the following in mind:
• Delayed childbearing A woman’s fertility starts to decline after about age 30. Advancing maternal age coupled with a medical cause of infertility significantly increases a woman’s risk of infertility.
• Smoking Cigarette smoking decreases the amount