If left untreated, chlamydia can progress to serious reproductive and other health problems with both short- and long-term consequences. Like the disease itself, the damage chlamydia causes is often “silent.” Complications in women from untreated chlamydia include:

• Pelvic inflammatory disease (PID). Chlamydia can spread into the uterus or fallopian tubes and cause pelvic inflammatory disease. PID is an infection of the uterus, fallopian tubes and other reproductive organs. This happens in up to 40 percent of women with untreated chlamydia. Although it may cause no signs or symptoms, PID can damage the fallopian tubes, ovaries and uterus, including the cervix. Untreated PID can lead to abscesses in the fallopian tubes and ovaries. The infection can cause scarring that may lead to infertility. PID affects up to 1 million women in the United States, and half of all cases may be due to an untreated chlamydial infection.
  
  
• Infertility (the inability to become pregnant after a year of continuous attempts). Chlamydial infection can scar the fallopian tubes, preventing eggs from being fertilized.
  
  
• An ectopic or tubal pregnancy. In this condition, a fertilized egg becomes trapped during its passage and starts developing outside the uterus. This development usually occurs in the fallopian tube but sometimes in the cervix, ovary or abdomen. The embryo must be removed to prevent rupture of internal organs.
  
  
• Chronic pelvic pain. Untreated chlamydia can result in scar tissue, which can cause continual pain. 
  
  
• Human immunodeficiency virus (HIV). Women infected with chlamydia are more likely to get HIV if exposed to the virus. The reason for the increased risk is that chlamydia causes a spike in the number of leukocytes, immune system cells, at the site of infection. Some of these leukocytes are needed to fight the infection but HIV can infect the leukocytes.
  
  
• Fitz-Hugh-Curtis syndrome. Patients with chlamydia sometimes develop Fitz-Hugh-Curtis syndrome, which involves inflammation of the liver. It is most often seen in cases of PID.
  
  
• Reiter’s syndrome. Rarely, genital chlamydial infection can cause Reiter’s syndrome, which is arthritis (inflammation of the joints) that can be accompanied by skin lesions (abnormal tissue) and inflammation of the eye and urethra (the tube that carries urine from the bladder to the outside of the body).
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• Cervical cancer. Some studies show a greater risk of cervical cancer among women with current or past chlamydial infections.

In pregnant women, chlamydia infections may lead to premature delivery. Babies born to infected mothers can develop neonatal conjunctivitis (a severe eye infection), which can lead to pneumonia (inflammation of the lungs) and other serious complications.