Chlamydia is spread primarily through sexual contact with an infected person, even if that person has no symptoms; it can be transmitted during vaginal, anal, or oral sex. It is also transmitted in some cases from an infected mother to her baby during vaginal childbirth
Sexually active women and men can transmit chlamydia through sexual contact with an infected person. Chlamydia can be passed during vaginal, anal, or oral sex. Because there are often no symptoms, people who are infected may unknowingly pass chlamydia to their sex partners.
An infected mother can also pass chlamydia to her baby during vaginal childbirth. Babies born to infected mothers can get pneumonia or infections in their eyes, also called conjunctivitis.
The more sex partners a person has, the greater the risk of getting infected with chlamydia. Chlamydia is easily confused with gonorrhea, another sexually transmitted disease (STD). Gonorrhea and chlamydia have similar symptoms and can have similar complications if not treated, but the two STDs have different treatments.
Because the cervix (opening to the uterus) of teenage girls and young women is not fully matured, chlamydia is transmitted easier in sexually active teenagers.
Since chlamydia is transmitted by oral or anal sex, men who have sex with men are also at risk for chlamydial infection.