For many couples planning a baby, conception occurs quite easily within a few months of "trying." The average chance to conceive for a normally fertile couple having regular, unprotected intercourse is approximately 25 percent during each menstrual cycle. For others, conception is not so simple. About 12 percent of couples of childbearing age are unable to conceive within 12 months, a condition called infertility.

Infertility is not just a woman's problem. In about 40 percent of infertile couples, a problem with the male is the sole cause, or a contributing cause, of infertility. About 25 percent of infertile couples have more than one cause or factor related to their inability to conceive. About 10 percent to 15 percent of couples have no identifiable cause for their infertility after medical investigation.

When conception does not occur after one year of unprotected intercourse, after six months in women over age 35, or if there are known problems causing infertility, it's recommended for both partners to undergo a medical evaluation. Your health care provider will try to determine if you are ovulating regularly, your partner is producing healthy, viable sperm, the egg and sperm are able to unite and grow normally, or if there are any obstacles to proper implantation and maintenance of the pregnancy.

If you suspect you are experiencing infertility, seek medical consultation early. Your age and the duration of the infertility sometimes can affect the outcome of treatment.

Many different factors and problems can cause infertility, including problems in the female reproductive system, the male reproductive system, or a combination of the two. The following are some of the conditions or factors that may be associated with infertility:

• Ovulation problems. Ovulation problems may occur when the woman's reproductive system does not produce the proper amounts of hormones necessary to develop, mature, and release a healthy egg.
• Anatomical problems. Abnormal development or function of the female anatomy can prevent the egg and the sperm from meeting. The most common anatomical problem is blockage of the fallopian tubes.
• Endometriosis. Endometriosis is a condition in which the tissue that lines the uterus develops outside the uterus, usually on other reproductive organs. Each month, this misplaced tissue responds to the hormonal changes of the menstrual cycle by building up and breaking down, resulting in scar tissue.
• Birth defects. Birth defects that cause abnormal development and function of reproductive organs can affect fertility. One of the most common reproductive system birth defects occurs following a woman's exposure to DES (diethylstilbestrol) taken by her mother during pregnancy. Fetal DES exposure often causes abnormal development of the uterus and cervix.
• Infection. Pelvic inflammatory disease (PID) can lead to scar tissue in the uterus, fallopian tubes, and/or the ovaries, causing ongoing pelvic pain and the possibility of an ectopic pregnancy (in which the fertilized egg becomes implanted outside the uterus).
• Immunological problems. A problem with a woman's immune system can lead to pregnancy loss. Antibodies (immune or protective proteins) in a woman's system can fail to recognize a pregnancy, or there may be an abnormal immune response to the pregnancy. Women can also develop antisperm antibodies that attack and destroy sperm .

• Low or absent sperm production. Without proper numbers of healthy sperm, the chance of fertilization is decreased.
• Abnormal sperm function. Sperm must have proper motility and the ability to penetrate the egg.
• Varicocele. Varicocele is a condition in which varicose veins develop around the testes. It is a very common cause of male factor infertility and is usually treatable and reversible with surgery.