Chronic endometritis and fertility

Acute infection of the womb, such as after childbirth or a miscarriage, tends to cause fever, pain and discharge and needs urgent treatment. Chronic endometritis is different. It is a smouldering inflammatory state in which immune cells, particularly plasma cells, are found in the lining even though the person feels well.

It should also be separated from pelvic inflammatory disease, which the NHS describes as infection of the womb, tubes and ovaries, commonly caused by sexually transmitted infections. The two can coexist, but chronic endometritis refers specifically to the lining.

Inflammation changes the environment an embryo meets, and it is thought to disturb the lining normal cycle of preparation. Studies have found plasma cells more often in women who have had repeated unsuccessful embryo transfers or recurrent miscarriage. This is an association, and researchers are still working out how much of the difficulty is explained by endometritis alone.

Because the HFEA notes that some microbiome tests specifically look for bacteria associated with chronic endometritis, patients may meet the diagnosis through clinic marketing as well as through medical referral, so it helps to know what is supported by evidence and what is not.

In many women, the trigger is never confirmed. Possible contributors include bacteria such as those that normally live in the gut or vagina ascending into the womb, previous pelvic infection, retained tissue after a pregnancy loss, an intrauterine device, and abnormal cavity features such as polyps. A chlamydia test is routine in fertility investigations because treatable infection should not be missed.

There is no blood test for chronic endometritis. Doctors may suggest hysteroscopy, because the NHS lists fertility difficulties and recurrent miscarriage among its indications, and the camera can show redness, tiny polyp-like changes or a strawberry-like pattern in the lining. A biopsy, taken with a thin plastic sampler, is then examined, often with a stain that highlights plasma cells.

Laboratories differ in how many plasma cells they count as positive and in the stains they use, so results are not always comparable between hospitals. Some also culture the sample for bacteria. Discuss with your specialist whether testing is appropriate for your situation, since it is not a routine first-line test for everyone with delayed conception.

• Biopsy of the womb lining, ideally outside the heavy bleeding days.

• Hysteroscopy to look at the cavity.

• Swabs including chlamydia screening.

• Review of previous infection and surgery.

Antibiotics are the standard approach, and the choice depends on the organisms suspected, allergies and local guidance. The clinician sets the type and length of the course. Some centres repeat the biopsy afterwards to confirm that inflammation has resolved, and may give a second course if it has not.

Hormonal treatment or probiotics are sometimes added, but the HFEA rates microbiome testing grey across all categories, including for those with chronic endometritis, stating that there is insufficient moderate or high-quality evidence to know if testing followed by various treatments improves the chance of a baby. A trial referred to by the HFEA had completed but awaited full publication at the time of its page.

If treatment is given before an embryo transfer, clinics may time the next cycle after a negative follow-up test. Since the evidence is unsettled, outcomes are discussed in terms of possibility rather than promise. For those with recurrent miscarriage, other causes such as chromosomal abnormalities, clotting disorders, womb shape and thyroid problems are also assessed in parallel.

Fever, offensive discharge, worsening pelvic pain or heavy bleeding, particularly after a pregnancy loss, delivery or procedure, needs prompt medical review through your GP, NHS 111 or A&E.