Causes of infertility
There are many potential causes for infertility or reproductive problems.  Chronic illnesses, as well as their treatments, can lead to fertility problems.  Illnesses like diabetes and hypothyroidism can cause fertility problems. Insulin, antidepressants, and thyroid hormones may lead to irregular menstrual cycles, for example.  Or medication used to treat peptic ulcers or hypertension can cause male factor infertility, including problems with sperm production or their ability to fertilize the egg.  Furthermore, cancer treatments can lead to fertility problems, especially radiation therapy near the reproductive organs.  Finally, STDs might cause infertility.  Some sexually transmitted diseases can block the fallopian tubes, making pregnancy either impossible or putting a woman at risk for ectopic pregnancy.

Causes of infertility in women
Most cases of infertility in women arise from problems with ovulation. Without ovulation, there are no eggs to be fertilized. Irregular or absent menstrual periods are some signs that a woman is not ovulating normally.   For example, birth control pills might temporarily alter female sex hormone production, which can take some time to restore after a woman stops birth control pills. This problem is usually temporary, but might take longer than the woman wants.  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

Causes of infertility in men
Sometimes a man is born with problems affecting his sperm. Other times problems arise due to illness or injury. For example, cystic fibrosis frequently causes infertility in men. 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

Risk factors

Women - many things can affect a woman's ability to become pregnant or give birth. These include:

• age
• alcohol
• athletic training
• being overweight or underweight
• health problems that cause hormonal changes
• medications
• poor diet
• sexually transmitted diseases (STDs)
• stress
• tobacco smoking

Men - overall health and lifestyle can affect the number and quality of a man's sperm. Some things that may reduce sperm number and/or quality include:

• age
• alcohol
• cancer radiation treatment and chemotherapy
• drugs
• environmental toxins, including pesticides and lead
• health problems
• medicines
• smoking cigarettes

The embryo must be healthy and the woman's hormonal environment adequate for its development for the pregnancy to continue to full term. Infertility can result when any one of these factors is impaired. But what are the symptoms of possible infertility? And how long should a couple try to conceive before seeking medical help? To learn more about symptoms of infertility and reproduction disorders, continue reading our next section on Symptoms of Infertility now.