Risk factors are any elements that increase the risk of a person developing a disease or condition. However, not everyone with one or more risk factors will develop the disease. It is also possible that the disease will develop in people with no risk factors. Those factors known to increase a woman’s risk of pelvic inflammatory disease (PID) include:

• Age. Younger women (age 15 to 25) are more susceptible to PID because their cervixes are thinner and are more likely to transmit disease. Younger women are also less likely to have certain antibodies that help protect the cervix from infection. Women under age 25 account for most of the PID cases in the United States.
  
  
• Sexual activity. Most cases of PID are caused by bacteria commonly found in two sexually transmitted diseases (STDs). Therefore, conditions that put a woman at risk for STDs (having unprotected sex or multiple male sexual partners) also put her at risk for PID.
  
  
• Medical history. Women who have had a previous occurrence of an STD or PID are at greater risk for PID after further exposure to an additional STD or other bacterial infection of the reproductive organs.
  
  
• Use of douches. Women who use vaginal douches may increase their risk of PID. Douches can force bacteria from the vagina into the upper reproductive organs. Douching also can change the composition of the naturally occurring bacteria in the vagina (vaginal flora) and make it easier for harmful outside bacteria to be introduced farther inside the body.
  
  
• Use of intrauterine devices (IUDs). Women with IUDs are at slightly higher risk for contracting PID, usually shortly after the IUD is inserted. Testing for and possibly treating any STDs before the IUD insertion reduces this risk.
  

  

  
  

• Gynecological events or procedures. Any surgical procedure or condition that involves the reproductive organs can increase the risk for PID. These include endometrial biopsy, dilation and curettage, miscarriage, abortion and childbirth.

PID is extremely rare among women who are not menstruating, either from pregnancy, menopause or amenorrhea. PID is also less likely to occur among women who are not sexually active.

Most cases of PID are caused by one or both of the following STDs:

• Chlamydia. The most common STD in the United States. It often has no visible symptoms, but may cause irregular bleeding, vaginal discharge or pain during sexual intercourse in women. The Centers for Disease Control and Prevention (CDC) estimates that 40 percent of women with untreated chlamydia will develop PID.
  
  
• Gonorrhea. Another common STD that often causes no symptoms in women. When they do occur, symptoms may include vaginal discharge, itching, burning or tenderness. Irregular bleeding, abdominal pain or painful urination may also develop with this STD. Some women with gonorrhea (treated or untreated) will develop PID.

In addition, some PID cases may be caused by normally occurring vaginal bacteria that migrate to the upper tract of the reproductive organs. This bacterial movement may occur if menstrual blood flows backwards from the uterus to the fallopian tube.