This is the most common of all bacterial STDs. It may cause abnormal vaginal discharge, burning with urination, lower abdominal pain, spotting after intercourse, or bleeding between periods. However, chlamydia may cause no symptoms at all.

Chlamydia must be taken seriously because the infection can spread further into the uterus and fallopian tubes (pelvic inflammatory disease), which lead to infertility or tubal pregnancy.

Chlamydia can be treated and cured with antibiotics.