Pelvic inflammatory disease (PID) is an infection of one or more of the upper reproductive organs, including the uterus, fallopian tubes, and ovaries. The main cause of PID is through a sexually transmitted infection (STI) such as chlamydia, gonorrhea, or mycoplasma genitalium. These bacteria usually spread from the vagina to the uterus, fallopian tubes, and ovaries. PID can also be caused by normal bacteria found in the vagina, which can move up from the vagina or cervix and into the reproductive organs. PID is often caused by more than one type of bacterium, and it can sometimes be difficult for doctors to pinpoint which are responsible.

Factors that increase the risk of PID include being sexually active and younger than 25 years old, having multiple sexual partners, being in a sexual relationship with someone who has more than one sex partner, having sex without a condom, douching regularly, which upsets the balance of good versus harmful bacteria in the vagina and might mask symptoms, and having a history of pelvic inflammatory disease or a sexually transmitted infection.

In most cases, PID is caused by a bacterial infection spreading from the vagina or cervix into the womb, fallopian tubes, and ovaries. If left untreated, PID can cause problems getting pregnant, problems during pregnancy, and long-term pelvic pain. It is important to seek medical attention if you experience any symptoms of PID, such as pain in your lower abdomen and pelvis, unusual or heavy vaginal discharge that may have an unpleasant odor, unusual bleeding from the vagina, especially during or after sex, or between periods, and pain during sex.