What is pelvic inflammatory disease?
Pelvic inflammatory disease (PID) is a bacterial infection that affects a woman's upper reproductive organs, including the uterus, ovaries and, most commonly, the fallopian tubes.

These organs can become inflamed when bacteria spreads through the cervix (the opening that separates the uterus from the vagina) and into the uterus. The bacteria may occur naturally in the vagina or be introduced during sexual intercourse.

Unlike infections in other body parts, which are usually caused by one organism, PID infections frequently include multiple bacterial organisms.

How common is pelvic inflammatory disease?
According to the Centers for Disease Control and Prevention, more than 1 million women in the United States are diagnosed annually with PID. It is the most common cause of female infertility and is responsible for 100,000 cases of infertility annually.

What are the major complications of PID?
During a woman's monthly cycle, an egg is released by one ovary and travels through the fallopian tube to the uterus. For pregnancy to occur, the egg must be fertilized by sperm, usually in the fallopian tube, and then implant in the uterus. When PID scars the tissues of any of these organs, the egg may be blocked, which prevents fertilization.

PID is also the most common cause of ectopic pregnancy, which occurs when scar tissue prevents a fertilized egg from moving to the uterus and the egg implants and grows in the fallopian tube instead. If the pregnancy is not terminated, the growing embryo can rupture the tube and cause massive abdominal bleeding.