Pelvic inflammatory disease (PID) is an infection of the female reproductive organs. PID can be caused by a variety of bacteria, most commonly the bacteria that cause chlamydia and gonorrhea. Other bacteria that can cause PID include mycoplasma, ureaplasma, and anaerobic bacteria. PID can also be caused by viruses, fungi, or parasites. Unprotected sexual contact is the most common cause of PID, however, other potential causes include childbirth, miscarriage, medical procedures, and the insertion of an intrauterine device. Symptoms of PID include pain in the lower abdomen, irregular menstrual bleeding, fever, chills, and an unusual discharge from the vagina. If left untreated, PID can lead to serious long-term complications such as infertility, ectopic pregnancy, chronic pelvic pain, and an increased risk of pelvic infections.