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Causes of Infertility

Age plays an important role in fertility, particularly since many couples have postponed childbearing until their 30's and 40's.

  • Peak fertility in a woman occurs in her early 20's and declines substantially by age 35 and even more so after age 40. By the time a woman reaches menopause, few if any eggs may be available or functional.
  • As a man ages, the number of sperm decreases, along with sperm motility, thus reducing the chances of pregnancy occurring. Other age-related problems include low testosterone and prostate, erectile, or ejaculation problems.

Besides age, other factors that can affect fertility in both women and men include:

  • Underlying medical conditions, such as diabetes
  • Unhealthy lifestyle or habits, such as smoking, use of alcohol and/or drugs
  • Being very overweight or underweight
  • Exposure to chemicals or toxins
  • Excessive exercise

Although precise causes of infertility are sometimes unknown, there are certain problems common to people affected by it. Conditions may affect the release of eggs (ovulation), interfere with sperm movement, or affect fertilization or implantation of a fertilized egg, to name a few general examples.

In women, infertility may be caused by conditions such as:

In men, infertility may be caused by conditions such as:

  • Erectile dysfunction, a common cause, affecting 10 to 20 million American men
  • Problems with sperm, such as a low sperm count, poor sperm movement (motility), clumped or agglutinated sperm that are unable to swim to the egg and abnormally shaped sperm
  • An imbalance of hormones, such as testosterone, LH, and FSH
  • Enlarged veins around the testicles (varicoceles)
  • Obstructions that prevent sperm from being released during ejaculation
  • Mumps infection, which can cause inflammation of the testicles
  • Injury to one or both testicles
  • Acute illness or prolonged fever
  • Exposure of the testicles to excessive heat
  • Klinefelter syndrome

Infertility testing can be complex, expensive, and time-consuming, and often both partners may be required to undergo extensive physical examinations, blood tests, lifestyle evaluations, and/or imaging procedures (for example, ultrasound) to determine the cause.

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