Chlamydia is a bacterial infection that is spread by sexual contact. It is the most common sexually transmitted disease (STD) in the United States. Chlamydia infects the urethra in men and the urethra, cervix, or upper reproductive organs (or all three) in women. Chlamydia can also infect the rectum and the surface of the eyes and lining of the eyelids (conjunctiva).

An infected mother can pass chlamydia to her baby at birth. Between 50% and 75% of babies born to mothers with chlamydia get the infection. They may have it in the eyes, back of the throat, rectum, or vagina. Between 30% and 40% of babies infected with chlamydia at birth develop complications, such as conjunctivitis or pneumonia.

Having chlamydia increases your risk of becoming infected with human immunodeficiency virus (HIV) if you are exposed to HIV.

Risk factors for getting chlamydia include:

  • Having unprotected sex (not using condoms).
  • Having more than one sex partner.
  • Having a high-risk partner or partners. This includes people who have more than one sex partner or sex partners who have chlamydia.
  • Starting sexual activity before age 18.


*This information is courtesy of