The same organisms responsible for bacterial sexually transmitted diseases (such as chlamydia, gonorrhea, mycoplasma, staph, strep) cause 90% to 95% of all cases of pelvic inflammatory disease (PID). Although sexual transmission is the most common cause of PID, bacteria may enter the body after gynecological events or procedures such as IUD insertion (intrauterine device used for contraception), childbirth, spontaneous abortion (miscarriage), therapeutic or elective abortion, and endometrial biopsy.
In the United States, nearly 1 million women develop PID each year. It is estimated that 1 in 8 sexually active adolescent girls will develop PID before reaching age 20. Since PID is frequently underdiagnosed, statistics are probably greatly underestimated.
Risk factors include sexual activity during adolescence, multiple sexual partners, a past history of PID, a past history of any STD (sexually transmitted disease), and the use of non-barrier type contraceptives. Use of an IUD (intrauterine device) may increase the risk of developing PID at the time of IUD insertion. Oral contraceptives ("the pill") are thought in some cases to enhance cervical ectropion, a condition that allows easier access to tissue where bacteria may thrive. However, oral contraceptives may in other cases have a protective role against developing PID because they stimulate the body to produce a thicker cervical mucous, which is harder for semen (which may contain bacteria) to penetrate. This makes it harder for semen to transmit bacteria to the uterus.
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