Pelvic inflammatory disease explained: causes and treatment

What PID is and what causes it

PID happens when bacteria travel up from the vagina or cervix into the womb, fallopian tubes and ovaries, causing inflammation and infection. Most cases are linked to sexually transmitted infections, particularly chlamydia and gonorrhoea, which is why PID is more common in younger, sexually active women. Not every case is caused by an STI, though — other bacteria can sometimes be involved. The risk is higher with a new or multiple sexual partners and after certain procedures involving the womb. Because chlamydia in particular often causes no symptoms, an infection can quietly reach the upper organs before anyone realises, which is one reason regular sexual health testing matters for sexually active people.

Recognising the symptoms

PID can range from mild to severe, and some women have few symptoms at all, which makes it easy to miss. Common features include pain low down in the tummy or pelvis, pain during or after sex, and unusual vaginal discharge that may change colour or smell. Some women notice bleeding between periods or after sex, or heavier, more painful periods. More severe infection can cause fever, feeling generally unwell and significant pain. Because these symptoms overlap with other conditions, PID is not always obvious. Anyone with new pelvic pain, especially alongside abnormal discharge or bleeding, should be assessed, as early diagnosis makes treatment simpler and lowers the chance of lasting harm.

Why prompt treatment matters

Treating PID quickly is important because the infection can scar and damage the fallopian tubes. This scarring is what leads to the main long-term complications: difficulty getting pregnant, a higher risk of an ectopic pregnancy (where a pregnancy develops in the tube rather than the womb), and ongoing pelvic pain. The longer treatment is delayed, or the more times PID recurs, the greater the risk to fertility. That is why clinicians often start treatment based on the symptoms and examination, before test results are back, rather than waiting. Acting early gives the best chance of clearing the infection before it can cause the scarring that has such lasting effects.

How PID is treated

PID is treated with a course of antibiotics, usually a combination chosen to cover the likely bacteria, including those causing chlamydia and gonorrhoea. Most people take these as tablets at home, but more severe infection may need hospital treatment. It is important to finish the whole course even if you feel better, and to rest and avoid sex until treatment is complete and any partners have been treated. Current and recent sexual partners should be tested and treated too, even if they have no symptoms, to prevent reinfection and onward spread. A follow-up review checks that the infection has settled. With prompt, complete treatment, most women recover fully.

Preventing PID and protecting fertility

Much of the risk from PID can be reduced. Using condoms lowers the chance of the sexually transmitted infections that cause most cases, and regular sexual health checks pick up infections such as chlamydia early, often before they cause symptoms or spread upwards. In England, free chlamydia testing is available for young adults, and testing is quick and confidential. If you are diagnosed with an STI, completing treatment and ensuring partners are treated prevents the ping-pong of reinfection. Seeking help promptly for pelvic pain or unusual discharge, rather than waiting to see if it passes, gives the best chance of catching PID early — the single most effective way to protect long-term fertility.