If untreated, chlamydia infection can cause serious reproductive and other health problems. Like the disease itself, the damage that chlamydia causes is often "silent."

In women, the chlamydia bacteria often infect the cells of the cervix. If not treated, the infection can spread into the uterus, fallopian tubes, and ovaries and cause pelvic inflammatory disease (PID). This happens in up to 40 percent of women with untreated chlamydia. PID can cause:

• Infertility. This is the inability to get pregnant. The infection scars the fallopian tubes, keeping eggs from being fertilized.
• An ectopic or tubal pregnancy. This means that a fertilized egg starts developing in the fallopian tube instead of moving into the uterus. This is a dangerous condition that can be deadly to the woman.
• Chronic pelvic pain. Pain that is ongoing, usually from scar tissue.

Untreated chlamydial infections can also cause inflammation of the bladder. Women who have chlamydia may also be more likely to get HIV, the virus that causes AIDS, from a person who is infected with HIV. In people having anal sex with a partner who has chlamydia, the bacteria can cause proctitis, which is an infection of the lining of the rectum. The bacteria causing chlamydia infections can also be found in the throats of people who have oral sex.

Untreated chlamydia in men typically causes infection of the urethra, the tube that carries urine from the body. Infection sometimes spreads to the tube that carries sperm from the testis. This may cause pain, fever, and even infertility.

In pregnant women, chlamydia infections may lead to premature delivery. Babies born to infected mothers can get infections in their eyes, called conjunctivitis or pinkeye, as well as pneumonia. Symptoms of conjunctivitis include discharge from the eyes and swollen eyelids, usually showing up within the first 10 days of life. Symptoms of pneumonia are a cough that steadily gets worse and congestion, usually showing up within three to six weeks of birth. Both of these health problems can be treated with antibiotics.