The female reproductive system is complex with many different organs and delicate set of hormones are subject to a variety of problems. Many factors can affect a woman’s ability to ovulate, conceive, or carry a pregnancy.

Often, multiple factors are to blame. In fact, in 25 percent of infertile couples, more than one factor contributes to infertility. They divide the causes of female infertility into four categories by location:

• Cervical
• Tubal
• Ovarian
• Uterine

Cervical factors

Unfortunately, sometimes more than one category is involved. Just because a problem in one of these categories is identified, it doesn’t mean you should stop looking for others. Be sure your doctor rules out other likely causes, including male factor infertility.

The cervix is a vital component in the female reproductive system. It is the conduit through which sperm must first pass from the vagina into the uterus, up the Fallopian tube, and, it is hoped, to an awaiting egg. Here are some cervical abnormalities that can impair conception or lead to miscarriage:

Malformations of the cervical canal.

Malpositioning of the cervix, which is rare.

Infections, which can produce poor quality, thick cervical mucus that can restrict or prevent sperm movement.

Injury from medical procedures, such as cryosurgery, cone biopsy, conization, or cauterization, which are often performed after abnormal Pap smear results.

Tubal factors

Damaged or malfunctioning Fallopian tubes account for 20 to 35 percent of the infertility cases treated. These abnormalities will prevent eggs from ever reaching the approaching sperm. The tubes may be blocked or immobilized by scar tissue, which makes it impossible for them to move and to pick up eggs.

Here are four possible causes of tubal disease:

• Infection
• Miscarriage
• Endometriosis
• Tubal sterilization

Ovarian factors

Ovarian disorders can prevent the development and ovulation of viable ova. Irregular or abnormal ovulation accounts for approximately 25 percent-some estimates place it as high as 33 percent-of all female infertility cases. Tell your doctor if you have abnormal periods, such as heavy flow or cramps, or irregularly occurring periods. These may signal ovarian dysfunction.

Here are some frequent causes of ovulation dysfunction:

• Thyroid disease
• Hypercortisolism
• Diabetes

Some less common ones are:

• Congenital abnormalities
• Polycystic ovarian disease (which is common in women who do not ovulate)
• Endometriosis
• Some drugs

Uterine factors

Uterine factors can interfere with fertility by:

• Causing structural problems, such as fibroids, polyps, or adhesions, which provide a poor environment.
• Preventing implantation of a fertilized egg into the uterine wall.
• Preventing embryo implantation.