Chronic Endometritis: The Overlooked Cause of Repeated Implantation Failure

When embryos look healthy and transfers go smoothly, it can be devastating when pregnancy still doesn’t occur. For many patients experiencing repeated implantation failure (RIF), the cause isn’t always obvious. One often-missed factor is chronic endometritis—a subtle, treatable inflammation of the uterine lining that can quietly interfere with implantation.

What Is Chronic Endometritis?

Chronic endometritis (CE) is a persistent inflammation of the endometrium, the lining of the uterus where implantation occurs. Unlike acute infections, CE usually does not cause pain, fever, or obvious symptoms. Many patients have no idea it’s present.

Instead, CE alters the uterine environment in ways that make it harder for an embryo to implant and develop properly.

How Chronic Endometritis Affects Implantation

A healthy endometrium is essential for implantation. Chronic inflammation can:

• Disrupt the immune balance needed for embryo acceptance
• Interfere with endometrial receptivity
• Alter cytokines and signaling pathways critical for implantation
• Increase the risk of implantation failure and early pregnancy loss

Studies have shown higher rates of chronic endometritis in patients with recurrent implantation failure and recurrent pregnancy loss, even when embryos are genetically normal.

Who Is at Risk?

Chronic endometritis can occur in anyone, but it is more common in patients with:

• Repeated failed IVF or frozen embryo transfers
• Unexplained infertility
• Recurrent miscarriage
• A history of uterine procedures (D&C, hysteroscopy, IUD use)
• Prior pelvic or uterine infections

Because symptoms are often absent, CE can easily go undetected without targeted testing.

How Is Chronic Endometritis Diagnosed?

Standard ultrasounds and routine fertility tests often miss chronic endometritis. Diagnosis typically requires:

• Endometrial biopsy
• Specialized staining (CD138) to identify plasma cells
• Sometimes additional microbiology or molecular testing

This testing is usually done in the luteal phase or as part of a targeted evaluation for repeated implantation failure.

Treatment: Why This Diagnosis Matters

The good news is that chronic endometritis is highly treatable.

Treatment often includes:

• A course of targeted antibiotics
• Follow-up testing to confirm resolution before embryo transfer

Research shows that treating chronic endometritis can significantly improve implantation and pregnancy rates, especially in patients who previously experienced repeated failures.

When Should You Consider Testing?

If you’ve experienced:

• Multiple failed embryo transfers
• Implantation failure with euploid (genetically normal) embryos
• Unexplained infertility despite thorough testing

…it may be time to ask whether chronic endometritis has been evaluated.

The Takeaway

Repeated implantation failure isn’t always about embryo quality. Sometimes, the issue lies in the uterine environment itself. Chronic endometritis is a quiet, overlooked condition, but identifying and treating it can make a meaningful difference in fertility outcomes.

If implantation hasn’t happened despite doing “everything right,” exploring hidden inflammatory causes may be the missing piece.