Cause

PID, sexually transmitted infection (STI), and bacterial vaginosis

Pelvic inflammatory disease (PID) is usually caused by a sexually transmitted infection (STI) that infects the cervix, which connects the upper vagina to the uterus. When the cervix is infected with an STI, it becomes easier for other bacteria present in the vagina to get into and infect the uterus and fallopian tubes. PID can also develop as a result of bacterial vaginosis (BV), which is a drop in the vagina's "good" organisms and an increase in its potentially "bad" organisms. When this happens and the problem organisms spread into the uterus and fallopian tubes, PID can result. (BV is not sexually transmitted.) See a picture of the female pelvic organs.

The most common causes of PID are:

• Gonorrhea, a sexually transmitted bacterial infection.
• Chlamydia, a sexually transmitted bacterial infection. PID caused by chlamydia is most common among teenagers and young adult women.

PID caused by chlamydia may have milder symptoms or no symptoms (compared with PID caused by gonorrhea), which can delay diagnosis.

Practicing safe sex by using condoms prevents STIs. This greatly lowers PID risk. For more information, see the Prevention section of this topic.

For more information, see the topics Gonorrhea, Chlamydia, and Bacterial Vaginosis.

PID and intrauterine devices (IUDs)

Women who have an intrauterine device (IUD) inserted for birth control have a higher risk of getting PID in the first month after insertion, especially if bacterial vaginosis or an STI is present at the cervix at the time of insertion. The insertion procedure may transfer bacteria from the vagina or cervix to the uterus. Your risk of infection can be reduced if:

• You are tested and treated for STIs and bacterial vaginosis (if detected) before IUD insertion.
• The insertion is done carefully to minimize the chance of infection (clean technique).

PID that spreads to abdominal organs

PID can spread to other abdominal organs, either from the pelvic organs through the lymphatic system or from the far ends of the fallopian tubes. This may be more common in women who have just:

• Given birth.
• Had uterine tests or other procedures, such as:
  • Taking a tissue sample of the uterine lining (endometrial biopsy).
  • Scraping the lining of the uterus (dilation and curettage, or D&C).
  • Examining the uterus or fallopian tubes with a lighted viewing tube (hysteroscopy or hysterosalpingogram).
• Had an abortion.