Chlamydia is one of the most common STDs and is the leading cause of preventable infertility in the US. If left untreated, it may lead to pelvic inflammatory disease and the risk of ectopic pregnancy in women. Most people don’t have any symptoms, but those who do might have unusual genital discharge or painful urination. Chlamydia can be spread by oral, anal or vaginal sex. A urine test is the easiest way to detect Chlamydia, and it's with antibiotics.