Causes

Many types of bacteria can cause PID, but gonorrhea or chlamydia infections are the most common. These bacteria are usually acquired during unprotected sex.

Less commonly, bacteria can enter your reproductive tract anytime the normal barrier created by the cervix is disturbed. This can happen during menstruation and after childbirth, miscarriage or abortion. Rarely, bacteria can also enter the reproductive tract during the insertion of an intrauterine device (IUD) — a form of long-term birth control — or any medical procedure that involves inserting instruments into the uterus.