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Causes of Infertility

Age plays an important role in female and male fertility, particularly since many couples have delayed childbearing until their 30's and 40's. Aging has been associated with damaged DNA in the egg and/or sperm or with hormonal imbalances that may develop over time. 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 impregnation. Other age-related problems include decreased testosterone production and prostate, erectile, or ejaculation problems.

Although precise causes of infertility are sometimes unknown, there are certain problems common to those suffering from it. In female infertility, common factors include:

A woman's fertility may also be affected by factors such as fluctuating or diminished hormone levels, inconsistent ovulation, or a poor reproductive environment that may interfere with sperm transport or fail to support proper fertilization or implantation of a fertilized egg.

A man's fertility can be affected by factors such as a low sperm count, poor sperm movement (motility), clumped or agglutinated sperm that are unable to swim to the egg, abnormally-shaped sperm, enlarged veins around the testes (varicoceles), obstructions that prevent sperm from being released during ejaculation, and genetic or congenital conditions that impair the reproductive environment. Primary male infertility is present when decreased serum levels of testosterone, LH, and FSH are present. One of the more common causes of male reproductive failure is erectile dysfunction, affecting 10 to 20 million American men. Other prohibitive causes include:

  • A history of having mumps
  • Testicular injury
  • Exposure to chemicals or toxins
  • Acute illness or prolonged fever
  • Exposure of the testicles to excessive heat
  • Drugs (marijuana, opiods, cimetidine, corticosteroids, methotrexate, antineoplastic drugs) or alcohol use
  • Use of anabolic steroids
  • Hormonal imbalances
  • Klinefelter syndrome

Infertility testing can be complex, expensive, and time-consuming, and often both partners are required to undergo extensive physical examinations, blood tests, evaluation of lifestyles, couples therapy, and/or ultrasound testing to determine the cause. Learn more about testing on the next pages of this article.

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