Chronic Endometritis and Fertility: What It Has to Do With Embryo Implantation

If you have been trying for a baby for a while, or you have been through an embryo transfer that didn’t implant, it is natural to want to understand in detail what is going on inside your uterus. One of the topics you may hear about in consultation is chronic endometritis, an inflammation of the uterine lining that often comes without obvious symptoms.

In this post we explain what it is, how it may relate to embryo implantation, how it is diagnosed and what you can do with that information to decide your next step.

Chronic endometritis: what it is and what it means for your fertility

The endometrium is the layer that lines the inside of the uterus and, every month, it changes to be able to receive a possible embryo. Chronic endometritis is a persistent, low-grade inflammation of this tissue. Unlike an acute infection, which usually causes fever or intense pain, in most cases it progresses silently and can go unnoticed for a long time. It should not be confused with endometriosis, in which tissue similar to the endometrium grows outside the uterus.

When symptoms do appear, they tend to be subtle and easy to mistake for something else: light bleeding between periods, vaginal discharge that is different from usual, mild pelvic discomfort or pain during sex. Many women notice none of them, which is why this diagnosis often comes up while investigating difficulty getting pregnant, without any earlier warning sign.

Its origin is mainly associated with the presence of bacteria in the uterine cavity, a space that normally keeps a tightly controlled environment. Some histories may be linked to it, such as previous gynecological infections, procedures inside the uterus, or earlier births and pregnancy losses, although in many cases no clear trigger is identified.

Receiving this diagnosis does not mean, on its own, that you can’t have a baby. Nor does it mean you did something wrong or that your uterus has stopped working. It is a finding that can be studied, that in many cases has medical treatment, and that gives your specialist valuable information to plan the next steps.

Knowing that chronic endometritis exists allows you to ask better questions in consultation and to understand why, in certain cases, it is worth taking a closer look at the environment where the embryo needs to implant.

Chronic endometritis and embryo implantation: why the endometrium matters so much

For embryo implantation to happen, the embryo and the endometrium need to meet at the right moment. For a few days in each cycle, known as the implantation window, the endometrium develops the conditions that allow it to recognize the embryo, let it attach and support its earliest stages. This ability is called endometrial receptivity.

Chronic endometritis can alter that environment. When inflammation persists, the number and type of immune cells present in the endometrium change, as do some of the chemical signals that regulate its communication with the embryo. Several studies have observed that this inflammatory environment can interfere with the preparation of the tissue and, in some cases, make it harder for the embryo to implant or for the pregnancy to continue.

For this reason, chronic endometritis tends to be investigated more closely in two situations. The first is recurrent implantation failure, meaning several embryo transfers with good-quality embryos that have not implanted. The second is recurrent pregnancy loss. Some studies have found this diagnosis more often in these groups than in women without that history, although the figures vary considerably from one study to another.

Even so, chronic endometritis explains only part of the story. Implantation also depends on the quality and chromosomal makeup of the embryo, your age, hormonal preparation and the shape of the uterine cavity. Conditions such as polyps, adhesions or some uterine fibroids can have a similar effect, and sometimes several factors coexist. In The uterine environment also matters we take a closer look at that invisible factor.

That is why finding inflammation in the endometrium is rarely enough on its own to explain a transfer that didn’t turn out as hoped. What it does provide is one more piece of the picture, one your specialist can integrate with the rest of your tests to understand more clearly what is happening in your case.

Chronic endometritis is diagnosed with an endometrial biopsy, often guided by hysteroscopy

How chronic endometritis is diagnosed

Because it is usually silent, chronic endometritis is almost never diagnosed from symptoms. The test that confirms it is an endometrial biopsy: a small sample of the tissue lining the uterus is taken and analyzed in the laboratory for plasma cells, a type of immune cell that normally should not be there. To identify them more precisely, a special stain is used, called CD138 immunohistochemistry.

That sample can be taken in the office, with a thin cannula, or during a hysteroscopy, a procedure in which a very fine camera is passed through the cervix to look at the cavity from the inside. Hysteroscopy makes it possible to see signs that suggest inflammation, such as a reddened endometrium, small reddish spots or micropolyps, while also ruling out other abnormalities of the cavity. Still, what is seen through the camera points the way, and the biopsy is what confirms.

In some cases the specialist also orders cultures or tests to identify the bacteria present. Not all centers use the same criteria for counting plasma cells, which is why the result is always interpreted together with your history and the rest of your tests.

When to see a reproductive medicine specialist

Seeking a specialized evaluation gives you concrete information to decide with more peace of mind. A consultation helps you organize what you already know, identify what still needs to be studied and avoid repeating steps that may not answer your questions.

It may be a good time to see a specialist if any of these situations sounds familiar:

• You have had two or more embryo transfers with good-quality embryos that did not implant.
• You have experienced two or more pregnancy losses.
• You have been trying for a baby for a while and your basic tests come back within the expected range, a situation sometimes described as unexplained infertility.
• You have bleeding between periods, unusual discharge or persistent pelvic discomfort, and you plan to start an assisted reproduction treatment.
• You have a history of gynecological infections or procedures inside the uterus.

If chronic endometritis is confirmed, management is usually based on a course of antibiotics that your specialist prescribes according to your case. In some situations the biopsy is repeated to confirm that the inflammation has resolved before scheduling a new transfer. Several studies have observed better implantation rates in treated women compared with those who received no treatment, although research continues and the response can vary from one person to another. That is why it is important to avoid self-medication and to make every decision with medical guidance.

At Ingenes, this analysis is part of a broader view. Our reproductive medicine specialists review your history, your previous tests and how your body has responded to earlier treatments, and add a genetic and metabolic perspective when your case calls for it. From there, they may recommend endometrial tests, adjust the preparation for a transfer or consider treatments such as IVF.

Our first consultation is designed precisely for that first step: getting to know your history, integrating the information you already have and defining what needs to be evaluated.

Frequently asked questions

Is chronic endometritis the same as endometriosis?

No. Chronic endometritis is a persistent inflammation of the endometrium, the layer lining the inside of the uterus. Endometriosis is a condition in which tissue similar to the endometrium grows outside the uterus. They are diagnosed and treated differently.

Does chronic endometritis cause symptoms?

In most cases, no. When they appear, they are subtle: light bleeding between periods, discharge that is different from usual, mild pelvic discomfort or pain during sex. That is why it is usually detected while investigating difficulty getting pregnant.

How is the diagnosis confirmed?

With an endometrial biopsy that is analyzed for plasma cells using a stain called CD138. The sample can be taken in the office or during a hysteroscopy, which also allows the uterine cavity to be examined from the inside.

Can it be treated?

Yes. It is usually treated with antibiotics prescribed by the specialist and, in some cases, the biopsy is repeated to confirm the inflammation has resolved before a new transfer. It is important not to self-medicate.

If I have chronic endometritis, does that mean I can’t have a baby?

Not necessarily. It is a finding that can be studied and treated, and it provides information to plan the next steps. Implantation depends on several factors, such as embryo quality, your age and the preparation of the endometrium.

Understanding your endometrium before trying again

Chronic endometritis is usually silent, and that is exactly why it is worth knowing about. An inflammation that gives no warning can change the environment where the embryo is trying to implant, and understanding it lets you look at your history with information instead of guesswork.

If you have been through transfers that didn’t implant, or losses that still hurt, give yourself time to ask what else can be studied. Sometimes the next step is understanding your endometrium better before trying again, and that pause is also part of the journey.

When you feel it is your moment, at Ingenes we will be here to listen and support you, with science on our side and our eyes on what you want most: your baby.