Usually, pelvic inflammatory disease is caused by bacteria that are transmitted by sexual contact.

The most common bacteria that cause pelvic inflammatory disease include:

• Gonorrhea
• Chlamydia

Pelvic inflammatory disease may also be caused by exposure to bacteria during another event, rather than by sexual contact.

Events that may cause pelvic inflammatory disease include:

• Childbirth
• Elective abortion
• Spontaneous miscarriage
• Endometrial biopsy:
• Sample of tissue is removed from the uterus
• Insertion of an IUD