Ever wonder why sexually transmitted infections (STIs) can lead to fertility issues? One important part of the answer is pelvic inflammatory disease (PID).
PID is an infection of the vaginal and upper genital tract in people with ovaries. It affects over two million people with ovaries in the US every year. And 12.5% of them will face post-PID infertility, and around 25% will develop chronic pelvic pain.
Here, we’ll explore PID’s causes, risk factors, treatments, and outcomes, with a big focus on the role it plays with fertility.
Here are your biggest takeaways:
- In the majority of cases, PID is caused by asymptomatic, untreated STIs, that have spread through the genital tract unnoticed.
- While PID is treatable, the scarring it can cause in the genital tract, and sometimes subsequent infertility, is often expensive or challenging to treat. PID is estimated to be involved in about 15% of female-factor infertility cases in the US.
- Research supports a correlation between increased sexually transmitted infection (STI) screenings and fewer instances of PID.
What is PID?
PID is known as an "ascending" infection — it starts in the lower genital tract (the vagina and cervix) and progresses to the upper genital tract (fallopian tubes, uterus, ovaries) as it spreads.
How PID is categorized depends on how it presents, persists, and whether a clinical cause has been pinpointed:
- Acute PID: When PID symptoms come on suddenly or severely, it’s defined as acute PID. It can cause long- and short-term symptoms, including pelvic and abdominal pain, as well as infertility and an increased risk of ectopic pregnancy.
- Subclinical PID: When PID is largely asymptomatic or presents atypically, it’s called subclinical PID. It’s often diagnosed when markers of pelvic inflammation, like blocked fallopian tubes due to scarring, disease, or damage, are present.
- Recurrent PID: Multiple instances of PID can occur if the initial infection is not treated adequately or a patient contracts a primary infection again.
What causes PID?
In at least 85% of cases, PID is caused by untreated chlamydia and gonorrhea — two of the most common sexually transmitted infections (STIs).
The other 15% of cases of PID may be caused by a mixture of other types of bacteria that have traveled up the reproductive system and caused an infection, like mycoplasma genitalium bacteria (a less common STI) and the pathogens that lead to bacterial vaginosis (the most common vaginal infection).
“Once a woman has had PID,” says OB-GYN and Modern Fertility medical advisor Dr. Jane van Dis, “the damage caused by the infection can make her more susceptible to future infections in the same area, thus increasing further risk of infertility.”
What are the symptoms of PID?
While subclinical PID will often initially present with no symptoms, or atypical, non-disruptive symptoms, acute PID is more likely to have clinically measurable symptoms. This could mean subclinical PID, sadly, is more likely to go unnoticed.
Common signs of PID include:
- Pain in the lower abdomen
- “Unusual" vaginal discharge with an odor
- Pain and/or bleeding during sex
- Burning during urination
- Bleeding between periods
Can PID have long-term, chronic impacts?
Complications caused by PID include chronic pelvic pain, infertility, ectopic pregnancy, and high susceptibility to developing PID again. These complications are usually related to damage and scarring of reproductive organs and prolonged inflammation, including:
- Formation of scar tissue both outside and inside the fallopian tubes that can lead to tubal blockage (linked to tubal factor infertility)
- Ectopic pregnancy (pregnancy outside the womb) which can be life threatening
- Long-term pelvic/abdominal pain
- Tubo-ovarian abscess
- Hydrosalpinx: Blockages and bloating within the fallopian tubes, a leading cause of tubal-factor infertility (TFI). An inability to get pregnant is often the first noticeable symptom, and this condition impacts IVF outcomes negatively, too.
How is PID diagnosed and treated?
PID is diagnosed by pelvic examination, tests for STIs, and tests for other infections. Testing may include genital tract swabs, blood samples, ultrasounds, and biopsies.
- A positive swab result confirms PID, but a negative swab result doesn’t necessarily indicate that PID isn’t present. Swab tests can give false negatives, too.
- Mild and moderate PID is typically treated with antibiotics. More severe and long-term cases may require surgical intervention, abscess drainage, or extended antibiotic treatment.
Does PID impact fertility?
While PID is treatable, the scarring it can cause in the genital tract, and sometimes subsequent infertility — is often not.
Both acute and subclinical PID can result in infertility by damaging the reproductive organs, causing blockages, or disrupting reproductive processes. Some of these damages, for instance to the tiny cilia lining the fallopian tube tract, are not visible to the naked eye. Infertility outcomes from PID can be difficult to treat because the structural genital tract changes set in motion by PID (like blockage of the tubes due to scar tissue) are usually permanent.
Around 15% of female infertility in the US is estimated to be PID related. This becomes more likely as soon as an infection spreads beyond the cervix, and when there is permanent injury to the fallopian tubes, like loss of ciliary action, fibrosis, and tubal blockage.
Risk factors for PID-related infertility
Among causes of PID, chlamydia appears to carry the greatest risk of infertility, because it’s often asymptomatic. One study suggests this could also be linked to individual immune responses to chlamydia, and a greater inflammatory response.
The risk of infertility grows when:
- Care for PID is delayed: One study found women with PID who delayed treatment for three or more days, were three times more likely to become infertile. (For this reason, seeking out care ASAP is essential.)
- Increased number of PID episodes: A review found a correlation between declining pregnancy rates and an escalating number of repeated PID infections.
- Severity of infection: Rates of live births in women with mild, moderate, and severe PID declined negatively, as severity increased in one study, too.
- Fallopian tube damage: This accounted for almost 70% of infertility cases in one study, with ectopic pregnancy rates of 9.1 in the clinical PID group (compared to 1.4% within the control group).
Infertility becomes notably more likely after the onset of either subclinical or clinical PID, generally, too:
- Clinical PID: The same study found 16% of participants with clinical PID were not able to conceive, compared to only 2.7% of the control group.
- Subclinical PID: Another study into women who had all previously proven fertile, found they were 40% less likely to conceive following the onset of subclinical PID.
Can you have PID while pregnant?
Though uncommon, when PID does coincide with pregnancy, it’s more likely to occur in the first trimester. If caught early, it’s still possible to treat with antibiotics, most likely intravenously (though some types are best avoided in pregnancy). But PID during pregnancy is still a risk factor for serious complications, including an increased risk of:
- Pregnancy loss
- Ectopic pregnancy, especially if PID was present around the time of conception.
- Preterm birth
- Maternal death in severe cases, particularly when an untreated ectopic pregnancy, caused by PID, results in a tubal burst and dangerous internal bleeding.
PID can also present as a postpartum infection within six weeks of giving birth, usually as inflammation of the womb lining. This is more likely to occur after a cesarean birth, with a prevalence rate of only 1-3 out of 100 women who give birth vaginally.
Dr. van Dis adds, “Women who are pregnant can become infected with PID prior to becoming pregnant as well as during their pregnancy. These infections must be treated with antibiotics as soon as they are recognized for the health of both the mother and the developing fetus.”
Can PID be prevented?
All people with ovaries who are sexually active are potentially at risk of PID, though there are steps you can take to limit your exposure. If you’re sexually active and not trying to conceive just yet (or ever), using barrier methods during intercourse is a great preventative step.
People with ovaries whose partners use condoms consistently and correctly are less likely to develop recurrent PID or infertility. Though not perfect, use of condoms can reduce the chance of infection by 30-60%.
Importantly, the CDC recommends all healthcare providers, including doctors, nurse practitioners, health clinics – basically anyone that cares for young women screen the following:
- All women who are sexually active (with men or women) who are less than 25
- All women 25 and older who
- Have a new sex partner
- Have more than 1 sex partner
- Have a sex partner with concurrent partners
- Have a sex partner who has a STI
- Retest all women approximately 3 months after treatment
- Consider rectal chlamydia testing based on reported sexual behaviors
- All pregnant women under 25
Screenings for STIs can be done at college health centers, by your private physician or nurse practitioner, at Family Planning Clinics or Title X clinics, at Planned Parenthood, at local health clinics, at LGBTQ+ health centers, urgent care clinics, at community health centers, and even through online providers.
The bottom line
PID can lead to both chronic pain and infertility outcomes. And subclinical PID might pose an increased risk to fertility, because it often goes undetected. Plus, diagnostic tools for subclinical PID aren’t as clear-cut, until someone presents with unexplained infertility or a tubal blockage.
Sexually transmitted infections are the most common cause of PID, and they can often be asymptomatic. Getting tested for STIs (and encouraging any sexual partners to do the same) and using barrier methods like condoms are two of the best ways protect yourself from PID.
This article was medically reviewed by Dr. Jane van Dis, MD, FACOG. Dr. van Dis is a practicing OB-GYN, Assistant Professor of Obstetrics & Gynecology at the University of Rochester, CEO of Equity Quotient, co-founder of OB Best Practice, and co-founder of TIME'S UP Healthcare.