Infection and inflammation of the female upper genital tract, including the uterus and fallopian tubes. Pelvic inflammatory disease (PID) is usually due to bacterial infection, including some sexually transmitted infections, such as chlamydia and gonorrhea. Symptoms, if any, include pain in the lower abdomen, fever, smelly vaginal discharge, irregular bleeding, or pain during intercourse. PID can lead to serious complications, including infertility, ectopic pregnancy (a pregnancy in the fallopian tube or elsewhere outside of the womb), and chronic pelvic pain.