Chronic Endometritis: Symptoms, Diagnosis & IVF Failure

Why Good Embryos Sometimes Fail to Implant

Many couples come to me after one or more IVF transfers with good-quality embryos that did not result in pregnancy. Embryo quality is only half the story. The embryo also needs a receptive uterine lining, and one of the more common, and most overlooked, problems with the lining is chronic endometritis.

This article is for education only and does not replace medical advice, diagnosis or treatment. Only a qualified doctor can diagnose uterine conditions after appropriate tests.

What Is Chronic Endometritis?

Chronic endometritis is a persistent, low-grade inflammation of the endometrium, the inner lining of the uterus. It is defined by the presence of plasma cells in the endometrial tissue, which are not normally found there.

It is thought to be caused mainly by low-grade bacterial infection. The bacteria commonly implicated include Enterococcus, E. coli, Streptococcus and Staphylococcus, as well as Mycoplasma, Ureaplasma and, less often, Chlamydia.

Acute vs chronic. Acute endometritis is a sudden illness, often after delivery, miscarriage or a pelvic procedure, with fever, pain and discharge. Chronic endometritis is quiet and can continue for months or years without making you feel unwell.

Not the same as endometriosis. Endometriosis is a different condition in which tissue like the uterine lining grows outside the uterus. See my guides on endometriosis stages and fertility and adenomyosis and fertility treatment for those.

Symptoms: Often None

Most women have no symptoms, which is why chronic endometritis is called a "silent" cause of infertility. When symptoms do occur they are mild and non-specific:

• Light spotting or brown discharge between periods
• A persistent, unusual vaginal discharge
• A dull pelvic ache or pressure, sometimes noticed after intercourse

Because these are so common and so mild, the condition is rarely found on a routine check-up. It is usually discovered during work-up for unexplained infertility, repeated implantation failure or recurrent pregnancy loss.

How It Affects Implantation

For an embryo to implant, the lining has to be receptive during a short "window of implantation". Persistent inflammation is thought to disturb that environment by:

• Changing the balance of immune cells and inflammatory signals in the lining
• Reducing the proteins that help an embryo attach to the uterine wall
• Altering blood-vessel growth and blood flow in the endometrium

Chronic endometritis has been linked with recurrent implantation failure in IVF and with early pregnancy loss. It is not the only cause of either, so it is one piece of a bigger investigation. Read more about implantation signs, the implantation window and failure, reasons for IVF failure and next steps and recurrent miscarriage causes and treatment.

How Chronic Endometritis Is Diagnosed

It cannot be seen on a routine scan or found with a standard blood test. Diagnosis usually combines:

Hysteroscopy

A thin telescope is passed through the cervix to look inside the uterus. Signs that suggest inflammation include small red spots (sometimes called "strawberry" spots), a swollen or pale lining and tiny micropolyps. Hysteroscopy also finds polyps, adhesions and other structural problems. See my hysteroscopy guide.

Endometrial biopsy

A small sample of the lining is taken in the clinic with a thin catheter. On routine staining, plasma cells can be hard to identify and can be missed.

CD138 immunohistochemistry

CD138 is a marker that stains plasma cells specifically. Applying it to the biopsy makes plasma cells much easier to spot and count under the microscope. This is the test most often used to confirm chronic endometritis. Laboratories differ on how many plasma cells count as a positive result, so results should be interpreted by your fertility specialist together with your history.

Treatment: Antibiotics and Re-Testing

Chronic endometritis is treatable. The general approach is:

1. A first-line antibiotic course, most commonly doxycycline for about two weeks, sometimes with an additional drug such as metronidazole if anaerobic bacteria are suspected. If a sexually transmitted infection is suspected, the partner should also be assessed and treated to prevent reinfection.
2. A repeat biopsy with CD138 testing after treatment, to confirm the inflammation has cleared. Not everyone clears it the first time.
3. A second-line regimen if inflammation persists, chosen by your doctor.

Never self-medicate with antibiotics. The right drug, dose and duration depend on your tests, allergies and other health factors.

Timing the Next Embryo Transfer

Once the inflammation has cleared, the aim is to transfer into a well-prepared lining. Studies suggest outcomes improve after chronic endometritis is treated, although the size of the benefit varies between studies and patients. I usually plan a frozen embryo transfer only after clearance is confirmed, so that a valuable embryo is not placed into an unprepared lining.

Lining thickness and receptivity

Lining thickness is checked on transvaginal ultrasound during the cycle. A thin lining has several causes, and chronic inflammation may be one of them. Read about what endometrial thickness is needed and foods that support the lining.

If implantation keeps failing even after chronic endometritis is treated, tests of endometrial receptivity such as the ERA test are sometimes considered to personalise transfer timing. The evidence for such tests is still evolving, so I recommend them selectively.

Who Should Be Tested?

Testing for chronic endometritis is worth discussing if you have:

• Had two or more failed embryo transfers with good-quality embryos
• Recurrent miscarriage
• Unexplained infertility after standard tests
• Persistent abnormal spotting or discharge

If you are unsure where you are in your journey, read Do you need IVF or can alternatives come first?

My Approach

I work through the uterine cavity systematically before repeating an IVF cycle: a hysteroscopy where indicated, biopsy with CD138 where appropriate, targeted treatment, and confirmation that the lining is clear. I bring the same attention to the lab side as an embryologist would, since a well-selected embryo deserves a well-prepared uterus. If you have had failed transfers or losses and want a structured review, book a consultation with Dr. Rukkayal Fathima.

Medical disclaimer: this article is general information. Diagnosis and treatment depend on your individual tests and history. Please consult a qualified fertility specialist.