Causes of Infertility

Reproduction involves several processes that must occur at exactly the right time. If there is an interruption in any of these processes, conception may not take place.

Each partner has a role in the reproductive process. For most women, one ovum, or egg, is released each month from one of the two ovaries and into the nearby fallopian tube. A man’s sperm passes from the vagina through the cervix and into the uterus. Fertilization occurs when one sperm penetrates the mature egg. The fertilized egg then continues through the fallopian tube into the uterus, where it implants into the uterine lining.

A women’s fertility peaks in her mid-twenties, starts to decline at about age 27 and drops off dramatically after age 35. The decline in fertility with age in women is most closely linked to the declining quantity and quality of eggs. For men, fertility begins to decline as early as age 35.

By the time the average female reaches puberty, the two million eggs she had at birth has decreased significantly to about 300,000. The quantity and quality of eggs declines with age, and it becomes increasingly more difficult to conceive.

For female infertility, some contributing factors may include:

  • Age
  • Polycystic ovary syndrome (PCOS)
  • Endometriosis
  • Irregular ovulation
  • Sexually transmitted infections (STIs)
  • Reproductive organ surgery
  • Smoking
  • Premature menopause
  • Cancer treatment

For male infertility, some contributing factors may include:

  • Age
  • Testicular surgery or injury
  • Exposure to chemicals or recreational drugs
  • Exposure to significant amounts of heat
  • Sexually transmitted infections (STIs)
  • Smoking
  • Hypothalamic/pituitary dysfunction
  • Congenital disorders
  • Structural abnormalities (i.e., varicoceles-an abnormal enlargement of the veins in the scrotum)
  • Hormonal and receptor abnormalities
  • Testicular cancer

The causes of infertility are unique in every case, but approximately 40% of fertility problems are due to a female factor and 40% are due to a male factor. In the balance of the cases, fertility problems result from problems in both partners or the cause of infertility cannot be explained.

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