Endometritis vs. Endometriosis: Why Everyone Mixes Them Up

Two conditions, almost the same name, and almost nothing else in common.

Endometritis and endometriosis get confused constantly, enough that multiple medical organizations publish explainer pages just to keep the two apart.

Endometritis is inflammation or infection of the uterine lining itself.

It's usually caused by bacteria, sometimes linked to a sexually transmitted infection, sometimes to childbirth, sometimes to a procedure. Acute endometritis tends to announce itself: fever, pelvic pain, abnormal bleeding or discharge. It's typically treated with a defined course of antibiotics and resolves.

Endometriosis is a different condition entirely. 

It happens when tissue similar to the uterine lining grows outside the uterus. Its cause is still being researched. It's chronic rather than something that clears with a two-week prescription, and treatment usually means hormonal therapy or surgery rather than antibiotics.

Where it gets genuinely confusing is chronic endometritis, a longer-lasting, often symptom-free version of the infection-based condition, not the tissue-growth one.

It frequently has no obvious symptoms at all, maybe occasional spotting, nothing more. 

That's part of why it's so often discovered by accident, found only because someone was already deep into a fertility workup, being tested for something else entirely, and a biopsy came back with an answer nobody had gone looking for.

Chronic Endometritis and Fertility: What the Research Actually Says

If you've been told your infertility, recurrent miscarriage, or repeated IVF failure is "unexplained," you already know how hard that word can be to sit with. Chronic endometritis is one of the things worth knowing about, not as a verdict, but as a possibility standard testing often doesn't check for.

Research reviewed by ESHRE and ASRM, the leading European and American reproductive medicine bodies, has found it present in more than half of the women studied across cases of recurrent implantation failure, recurrent pregnancy loss, and unexplained infertility. 

That figure varies depending on which diagnostic threshold a given study used, so it's worth treating "over half" as a rough midpoint rather than an exact number.

Both ESHRE and ASRM describe this fertility link as an observed association, not a settled fact. Researchers see chronic endometritis showing up often in these patient groups, but haven't confirmed it's the cause in every case, or that treating it reliably fixes the underlying fertility issue.

That matters, because the evidence on treatment is genuinely mixed. One review found significantly better live-birth rates in women whose chronic endometritis was successfully cured compared to those where it persisted. Another found no significant benefit from oral antibiotics. A third found no improvement at all. Both ESHRE and ASRM currently say that testing and treatment "can be considered," not that they're formally recommended, and both are calling for more randomized controlled trials before that changes.

What is more settled is how treatable the infection itself is.

Around 79% of women are cured after a single course of the antibiotic doxycycline, with the remaining 21% needing a second round or a different antibiotic. 

What's still thin is long-term data on whether it comes back months or years later.

None of this means chronic endometritis explains every unexplained case, and it's not a guarantee that treating it will change a fertility outcome. What it does mean is that it's a legitimate, researched possibility worth asking your care team about directly, especially if a biopsy of the uterine lining hasn't been part of your workup so far.

None of that makes the not knowing any less frustrating in the moment. If you've spent time cycling through appointments, tests, and "everything looks normal" without a clear answer, it's a reasonable thing to have found frustrating. None of this reflects anything you did or didn't do, it reflects how early this area of research still is.

Want to see the research behind this? Check the latest research in the TrialMe app and if you've been diagnosed with chronic endometritis, you may be eligible to take part in chronic endometritis research happening right now. 

Sources

Cleveland Clinic (2022), StatPearls / NCBI Bookshelf.

ESHRE Good Practice Recommendations on Recurrent Implantation Failure (2023), ASRM Committee Opinion on Recurrent Implantation Failure (2026), Frontiers in Endocrinology (2025), Reproductive BioMedicine Online (2022).

• What is chronic endometritis?

  Chronic endometritis is a long-lasting, low-grade inflammation of the endometrium, the tissue lining the inside of the uterus.
  It often causes few or no noticeable symptoms, so many people only hear about it during fertility investigations, for example after repeated IVF transfers that did not lead to pregnancy, or after recurrent miscarriage.

  It is usually diagnosed by taking a small tissue sample from the uterine lining (an endometrial biopsy) and looking for specific immune cells (plasma cells, often stained with a marker called CD138).
  Reported rates vary a lot between studies, which is one reason researchers are looking for simpler, less invasive ways to study it.

• What is the difference between endometritis and endometriosis?

  They're unrelated conditions that happen to sound alike. Endometritis is infection or inflammation of the uterine lining itself, usually bacterial. Endometriosis is a different, non-infectious condition where endometrium-like tissue grows outside the uterus.

• What are the symptoms of acute vs. chronic endometritis?

  Endometritis splits into two quite different clinical pictures.

  Acute endometritis tends to announce itself. Within about 30 days of the triggering event (an infection, childbirth, or a procedure like an IUD placement or D&C) you might develop fever, pelvic pain, abnormal vaginal bleeding or discharge, and a general feeling of being unwell.

  Chronic endometritis is the quieter. It can persist for 30 days or longer with minimal or no symptoms at all. Maybe some subtle abnormal bleeding or spotting between periods, but often nothing noticeable enough to flag on its own.
  As a result, chronic endometritis is frequently discovered not because someone felt unwell, but because they were being evaluated for something else entirely, most commonly, difficulty conceiving or repeated failed fertility treatment cycles.
  That's an important thing to know if you're heading into a fertility workup: chronic endometritis is one of several things your care team may be screening for, even without matching symptoms.

  This is general information, not a diagnosis. Persistent unusual bleeding or pelvic symptoms of any kind are worth discussing with a doctor.

• How is chronic endometritis diagnosed?

  The gold standard is an endometrial biopsy examined under a microscope for plasma cells in the uterine lining tissue. A special stain called CD138 makes those cells easier to spot. Hysteroscopy (a camera exam of the uterus) can suggest chronic endometritis but isn't diagnostic on its own.

• Can an IUD cause or be linked to endometritis?

  IUD insertion is a recognized risk factor for acute endometritis, simply because any procedure that passes through the cervix carries some infection risk, similar to other gynecological procedures.

  Separately, having an IUD in place long-term is associated with low-grade, foreign-body-related inflammation that can contribute to chronic endometritis in some cases.

  IUDs remain a very safe, effective, widely recommended form of contraception. Routine follow-up and appropriately timed replacement is the sensible way to manage this small, mostly asymptomatic risk.

  This is general information, not a reason to avoid or remove an IUD without medical guidance. If you have concerns, your gynecologist can advise based on your specific device and timeline.

• Is endometritis contagious or an STI?

  Endometritis isn't "contagious" in the sense that a partner could catch inflammation of your uterine lining directly.

  But acute endometritis very frequently has a sexually transmitted origin: CDC guidance notes that the substantial majority of acute cases (over 85%, per the data reviewed) are linked to sexually transmitted organisms, chlamydia being especially common. This is exactly why acute endometritis is usually treated and classified alongside pelvic inflammatory disease (PID).

  Chronic endometritis tells a different story. It's typically driven by other bacteria: often an overgrowth of organisms that are normally present in the vaginal flora in small numbers, rather than a sexually transmitted infection.

  Sources: CDC STI Treatment Guidelines, PID section, updated April 2023; StatPearls (NCBI Bookshelf), "Endometritis."

• What causes postpartum endometritis, and who is at risk?

  Postpartum endometritis is the single most common infection following childbirth.

  The clearest risk factor is delivery method: cesarean delivery carries roughly 5 to 20 times the risk of postpartum endometritis compared to vaginal delivery.

  Beyond delivery method, other documented risk factors include prolonged labor, ruptured membranes lasting an extended time before delivery, chorioamnionitis (infection of the membranes surrounding the baby), manual removal of the placenta, and underlying conditions including obesity, diabetes, HIV, anemia, or a prior history of pelvic inflammatory disease or bacterial vaginosis.

  Knowing the warning signs matters because postpartum endometritis needs prompt treatment: fever, foul-smelling vaginal discharge, and pelvic pain or bleeding that's worsening rather than improving after delivery are the signs to flag to your care team right away, rather than assuming they're a normal part of postpartum recovery.

  This is general information, not a substitute for postpartum medical follow-up. Any of the warning signs above should prompt a call to your provider.

  Sources: StatPearls (NCBI Bookshelf), "Endometritis"; patient.info, "Postpartum Endometritis," Oct 2024.

• How is endometritis treated, and how long does treatment take?

  For acute endometritis linked to an STI or classified as pelvic inflammatory disease, the CDC's standard regimen is a 14-day course combining three antibiotics: ceftriaxone, doxycycline, and metronidazole, chosen to cover the range of likely bacterial causes.

  For chronic endometritis, the most commonly used first-line treatment is doxycycline for 14 days. It's worth being upfront that the medical literature explicitly states there's no single standardized treatment protocol for chronic endometritis.

  If doxycycline doesn't resolve it, second-line antibiotics like levofloxacin, metronidazole, or ciprofloxacin are used instead.

  For postpartum endometritis, treatment typically begins with IV antibiotics (commonly gentamicin plus clindamycin) continued until you've been fever-free for 24 hours; an oral antibiotic course afterward isn't always necessary.

  This is general information about typical treatment approaches. Your specific regimen and duration should come from your treating clinician based on your case.

  Sources: CDC STI Treatment Guidelines; StatPearls (NCBI Bookshelf); Frontiers in Endocrinology review, June 2025; AJOG trial listing, 2025 (trial existence confirmed; results not yet verified).

• Is chronic endometritis linked to recurrent implantation failure or recurrent pregnancy loss in IVF?

  Yes, the association is well documented in the research literature: chronic endometritis has been found in roughly 55–57% of patients with recurrent implantation failure, recurrent pregnancy loss, or unexplained infertility across the studies reviewed. Both ESHRE (the European Society of Human Reproduction and Embryology) and ASRM (the American Society for Reproductive Medicine) formally acknowledge this link, but grade the evidence as coming from observational studies rather than settled, high-certainty fact.
  
  This is general information about a documented association, not a claim that chronic endometritis is the cause of any individual person's specific situation.

  Sources: Frontiers in Endocrinology review, June 2025; ESHRE Good Practice Recommendations on Recurrent Implantation Failure, June 2023; ASRM Committee Opinion on Recurrent Implantation Failure, 2026.

• Does treating chronic endometritis actually improve IVF or pregnancy outcomes?

  This is one of those questions where a confident-sounding answer would actually be misleading, so let's sit with the real uncertainty here.

  On one hand, there's a genuinely encouraging data point: one systematic review cited by ESHRE's own guidance found a substantially higher rate of live births and ongoing pregnancies among patients whose chronic endometritis was successfully treated and confirmed cured, compared to those whose inflammation persisted: a meaningfully large difference in that particular analysis.

  On the other hand, two additional reviews complicate that picture considerably. One found no statistically significant benefit from oral antibiotic treatment when the data was pooled, with a lot of inconsistency between the underlying studies. Another found no improvement in outcomes at all associated with treatment.

  Both ESHRE and ASRM describe the current evidence as observational rather than the gold-standard randomized-trial evidence that would let them make a firm recommendation. Their guidance language reflects that: testing and treating chronic endometritis "can be considered" as part of a fertility workup, rather than something formally recommended as proven to help.

  Both bodies explicitly call for more randomized controlled trials to settle the question properly.

  If you're navigating this personally, it's worth knowing you're in a genuinely unresolved area of medicine. Not that your doctor is being vague for no reason, and not that treatment is pointless, but that nobody can currently promise you it will change your outcome.

  This is general information about an actively evolving area of research, not a prediction about any individual's treatment response.

  Sources: ESHRE Good Practice Recommendations, June 2023; ASRM Committee Opinion on Recurrent Implantation Failure, 2026.

• Can chronic endometritis recur, and do you need a repeat biopsy to confirm it's cured?

  A retrospective cohort study looked at exactly this: after a first course of doxycycline, about 79% of patients were considered cured, meaning their CD138-positive cell counts dropped below the diagnostic threshold on follow-up testing. The remaining roughly 21% still tested positive and needed additional treatment, typically with a different antibiotic.

  Where the evidence runs thinner is longer-term: this research didn't establish solid data on relapse rates over the following months or years after a confirmed cure.

  This is general information based on one retrospective study, not a personal prognosis — your care team can advise on follow-up testing appropriate to your specific case.

  Source: Reproductive BioMedicine Online, "New biopsy after antibiotic treatment: effect on outcomes of assisted reproduction in patients with infertility and chronic endometritis," Aug 2022.