What causes infertility?
In only about one-third of cases is infertility due to the woman (female factors). In another one third of cases, infertility is due to the man (male factors). The remaining cases are caused by a mixture of male and female factors or by unknown factors.

Infertility in men is most often caused by:

    * problems making sperm -- producing too few sperm or none at all
    * problems with the sperm's ability to reach the egg and fertilize it -- abnormal sperm shape or structure prevent it from moving correctly

Sometimes a man is born with the problems that affect his sperm. Other times problems start later in life due to illness or injury. For example, cystic fibrosis often causes infertility in men.

Infertility in women is most often caused by problems with ovulation. Without ovulation, there are no eggs to be fertilized. Some signs that a woman is not ovulating normally include irregular or absent menstrual periods.

Less common causes of fertility problems in women include:

    * blocked fallopian tubes due to pelvic inflammatory disease, endometriosis, or surgery for an ectopic pregnancy
    * physical problems with the uterus
    * uterine fibroids