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).