Pelvic inflammatory disease and fertility: symptoms, treatment and what the long-term studies show

What pelvic inflammatory disease is

Pelvic inflammatory disease (PID) is an infection of the upper reproductive organs: the womb, the fallopian tubes and the ovaries. It usually starts with bacteria in the vagina or cervix that travel upwards. The NHS describes it as an infection that "can be easily treated with antibiotics" if it is diagnosed early, but warns that delayed or severe infections can cause lasting problems (NHS, Pelvic inflammatory disease).

The fallopian tubes are the reason PID matters so much for fertility. They are narrow, delicate channels where sperm meets egg and along which the fertilised egg travels to the womb. Inflammation can leave scar tissue that narrows or blocks them. A blocked tube stops sperm and egg meeting; a partly damaged tube may let sperm through but slow the embryo's journey, so that it implants in the tube instead of the womb.

What causes it

According to the NHS, PID is usually caused by sexually transmitted infections, especially chlamydia and gonorrhoea. It can also be caused by bacteria that normally live in the vagina. The NHS lists situations in which PID is more likely:

• a previous episode of PID;
• having given birth or had a miscarriage, which can damage the cervix;
• having a coil (IUD or IUS) fitted, a hysteroscopy, an abortion or any other procedure that opens the cervix.

Worldwide, the infections behind PID are very common. The World Health Organization estimated that in 2020 there were 129 million new chlamydia infections and 82 million new gonorrhoea infections among people aged 15 to 49, and it names these two infections as major causes of PID and infertility in women. The WHO also reports that gonorrhoea has become resistant to many antibiotics, which makes testing and correct treatment more important, not less.

Symptoms, and why many cases are missed

Not everyone with PID has symptoms. When they appear, the NHS lists:

• pain in the lower tummy or pelvis, between the tummy and the thighs;
• pain felt deep inside during sex;
• heavy or painful periods that are unusual for you;
• bleeding between periods or after sex;
• vaginal discharge that looks, smells or feels unusual.

Symptoms can start quickly over a few days, or develop slowly and get worse over time. Mild pain is easy to put down to a heavy period or a stomach upset. Chlamydia itself is often silent: the NHS says that most people who have chlamydia do not have any symptoms (NHS, Chlamydia).

The NHS advises asking for an urgent GP appointment, or contacting NHS 111, if you think you have symptoms of PID, if pelvic pain comes and goes, if you have symptoms and might be pregnant, or if you have been diagnosed and do not feel better after 3 days of antibiotics.

When it is an emergency

Call 999 or go to A&E if you might have PID and you have severe pelvic pain that is getting worse or hurts when you move, pelvic pain with heavy vaginal bleeding, a sharp, sudden and intense pain in the lower tummy, pain under the ribs on the right side and in the right shoulder, dizziness or fainting, a very high temperature or shivering, or you are being sick or feel very unwell. Some of these signs overlap with those of a ruptured ectopic pregnancy, which is one more reason not to wait.

How it is diagnosed

There is no single test for PID. A GP will ask about symptoms, recent sexual partners, contraception and whether you could be pregnant, then examine the tummy and pelvis. A vaginal examination, similar to cervical screening, allows swabs to be taken from the cervix and vagina to look for infections. Depending on the situation, a blood test, a pregnancy test, an ultrasound scan or a referral to a sexual health clinic may follow. You can ask for a female doctor and for a chaperone, and you can ask for the examination to stop at any time.

Because swab results take time and a negative result does not rule PID out, doctors often start treatment on the basis of symptoms and examination. Treating early is what protects the tubes.

Treatment

The main treatment is antibiotics. The NHS says the doctor will usually give an antibiotic injection and prescribe antibiotic tablets to take for 2 weeks; everyday painkillers such as paracetamol or ibuprofen can help with pain. Severe infections, or infections left untreated, may need hospital care.

Two parts of treatment are easy to overlook:

• Partners. If an STI is suspected, a sexual health clinic will contact recent sexual partners so that they can be tested and treated. Without this, the infection can simply come back.
• Waiting before sex. The NHS advises not having sex until you and your partners have finished antibiotics, your symptoms have gone and tests show the infection has cleared, and using a condom if you do.

The link with infertility: what a Swedish cohort found

Much of what is known about PID and fertility comes from a long-running study in Lund, Sweden, led by Lars Weström and published in 1992 (Weström et al., Sexually Transmitted Diseases, 1992). Between 1960 and 1984, 2,501 women with suspected PID had a laparoscopy, a keyhole examination that shows the tubes directly. In 1,844 of them the examination confirmed the disease; the 657 women whose tubes looked normal served as a comparison group. The researchers then followed what happened when these women tried to conceive.

The authors found that tubal infertility was linked to the number and severity of PID episodes. Two points help read these figures. First, most women in the study did conceive: PID raises the risk of infertility, it does not make it inevitable. Second, the cases date from 1960 to 1984, and diagnosis and treatment have changed since, so the exact percentages may not apply today. The direction of the findings, and the importance of repeated episodes, is what has lasted. PID is not the only cause of tubal damage: endometriosis and previous surgery can also affect the tubes.

Does testing for chlamydia prevent PID?

If chlamydia causes PID, finding and treating it early should prevent some cases. A randomised trial in London, the POPI trial, tested this idea. Published in the BMJ in 2010 by Pippa Oakeshott and colleagues, it recruited 2,529 sexually active female students with an average age of 21. Their swabs were either tested straight away, with treatment for anyone positive, or stored and tested a year later.

• About 1 in 18 women had chlamydia at the start (5.4% in the screened group, 5.9% in the deferred group).
• Over 12 months, 9.5% of untreated women who had chlamydia at the start developed PID, compared with 1.6% of those who were screened and treated.
• Overall, PID occurred in 1.3% of screened women and 1.9% of controls, a difference that was not statistically significant.
• Most cases of PID (79%) occurred in women who had tested negative for chlamydia at the start.

The authors concluded that the benefit of a single chlamydia test over 12 months may have been overestimated. A test helps the women who are infected at that moment; it says nothing about infections caught afterwards. That is one reason why the NHS advice is to test once a year and with every new partner, not just once. In England, people under 25 can order free home test kits.

Protecting fertility

• Use condoms with new or casual partners; they reduce the risk of chlamydia and gonorrhoea.
• Get tested regularly if you are sexually active, even without symptoms, and before having a coil fitted if you may have been exposed.
• Seek help early for pelvic pain, pain during sex or unusual bleeding or discharge, and finish the full course of antibiotics.
• Make sure partners are tested and treated, to avoid reinfection.
• If you are planning a pregnancy, an STI check fits naturally into the steps in what the official guidance recommends before trying for a baby.

Anyone who has had PID and is pregnant again should tell a GP or midwife early, because of the higher risk of ectopic pregnancy. People who have had PID and struggle to conceive can ask about tests that check whether the tubes are open; IVF, which bypasses the tubes, is an option when they are blocked.

This article summarises NHS information and published research. It is not personal medical advice. If you have pelvic pain, unusual bleeding or discharge, see a GP or a sexual health clinic; for severe pain, fainting or a high temperature, call 999.