Inflammation and Fertility: What Is Worth Testing and What Is Not

'Inflammation and fertility' covers two very different things, and conflating them is how people end up spending large sums on tests that change nothing.

Specific inflammatory conditions.

Named, diagnosable diseases affecting the reproductive tract — chronic endometritis, endometriosis, pelvic inflammatory disease, genital tract infection. These have defined diagnostic criteria, established effects on fertility, and in several cases effective treatment.

Generalised inflammatory markers.

Blood tests such as CRP, ESR, interleukin-6 and TNF-alpha, and the immune panels sold under headings like 'reproductive immunology'. These measure systemic inflammatory activity.

The first group is worth investigating when there is reason to. The second is not part of any mainstream infertility workup, and testing it rarely produces an action that helps.

The rest of this article deals with each in turn, because the practical advice is opposite in the two cases.

C-reactive protein is a general marker of systemic inflammation. It rises with infection, injury, autoimmune disease activity, obesity, smoking and recent illness.

The problems with using it to investigate infertility:

• It is non-specific — a raised CRP indicates inflammation somewhere, with no information about where or why
• It is not part of any major guideline's recommended infertility workup
• A raised result rarely produces a treatment decision that would not have been made anyway
• A normal result excludes nothing relevant, since chronic endometritis and endometriosis frequently occur with a normal CRP

The same applies to cytokine panels and most 'immune testing' offered for unexplained infertility and recurrent implantation failure. Natural killer cell testing is the most heavily marketed example: peripheral blood NK cells do not reliably reflect uterine NK cells, and the treatments offered on the strength of such results — intralipids, steroids, intravenous immunoglobulin — are not supported by good evidence and carry real costs and risks.

If a clinic proposes an inflammatory or immune panel, reasonable questions are: which specific condition is this testing for, what would we do differently depending on the result, and what guideline recommends it?

If inflammation matters in your case, this is the condition most likely to be relevant, and it is genuinely treatable.

Chronic endometritis is persistent, low-grade inflammation of the endometrium, usually driven by bacteria. It is largely silent — most women have no symptoms at all, which is why it goes undetected.

It is associated with:

• Recurrent implantation failure after IVF
• Recurrent pregnancy loss
• Unexplained infertility

Diagnosis is specific rather than inferred from a blood test:

• Endometrial biopsy showing plasma cells in the endometrial stroma
• CD138 immunohistochemical staining, which identifies plasma cells far more reliably than routine staining alone
• Hysteroscopy may show suggestive findings such as micropolyps and endometrial congestion, but is not diagnostic on its own

Treatment is generally a course of antibiotics, with a follow-up biopsy to confirm resolution. The evidence base has limitations — studies vary in diagnostic criteria and antibiotic regimens, and the effect on live birth is less firmly established than the association with implantation failure. It remains a reasonable thing to look for after repeated implantation failure or recurrent loss, precisely because it is specific, testable and treatable.

Both are inflammatory conditions, and both reduce fertility — but largely through structural damage rather than through inflammation in the blood.

Endometriosis

Endometrial-like tissue outside the uterus provokes a chronic inflammatory response. Effects on fertility include:

• Adhesions distorting pelvic anatomy and interfering with egg pickup
• Endometriomas affecting ovarian tissue and reserve
• An altered peritoneal environment that may impair sperm and egg function
• Possible effects on endometrial receptivity

Diagnosis is by laparoscopy, with imaging used for deep disease and endometriomas. No blood test diagnoses it — CRP will not, and neither will any currently marketed panel.

Pelvic inflammatory disease

Usually from ascending infection, frequently chlamydia or gonorrhoea. The fertility consequence is tubal damage — scarring, blockage, and hydrosalpinx. Damage is often permanent even after the infection is treated, and PID is frequently asymptomatic, so it may only surface when tubal blockage is found during an infertility workup.

Both illustrate the general point: what matters is the specific condition and the damage it causes, not a measurement of systemic inflammation.

This is the route by which generalised inflammation most clearly does affect fertility, and it is also the most modifiable.

Adipose tissue is metabolically active and releases pro-inflammatory mediators. The resulting chronic low-grade inflammation affects reproduction in both partners.

In men, a systematic review in Fertility and Sterility examined obesity and metabolic health in relation to male fertility. Mechanisms include:

• Disruption of the hypothalamic-pituitary-gonadal axis and testicular steroidogenesis
• Oxidative stress and mitochondrial dysfunction affecting sperm quality
• Raised scrotal temperature from surrounding adipose tissue
• Effects on sperm concentration, motility, viability and morphology

In women, associated effects include disrupted ovulation, insulin resistance, altered endometrial receptivity, and lower success rates in fertility treatment.

The practical point is that the useful intervention here is metabolic rather than immunological. Weight, activity, sleep, glycaemic control and smoking cessation act on the inflammatory state directly. Measuring CRP adds little to a plan that is already indicated on other grounds.

A workable approach:

1. Ask which specific condition is being considered, rather than accepting 'inflammation' as a diagnosis
2. For recurrent implantation failure or recurrent loss, ask specifically about chronic endometritis and CD138 staining, which is concrete and treatable
3. For pelvic pain, painful periods or painful sex, ask about endometriosis and how it would be assessed
4. Address metabolic factors, which act on inflammation and improve outcomes regardless
5. Before agreeing to any immune panel, ask what would change depending on the result

What to be cautious about:

• Packages of inflammatory or immune markers sold as a bundle for unexplained infertility
• Immune treatments — intralipids, steroids, IVIG — offered on the strength of peripheral blood results
• Anti-inflammatory supplement protocols marketed as fertility treatment
• Being given 'inflammation' as an explanation without a named condition behind it

There is a genuine role for anti-inflammatory eating patterns, exercise and sleep in general health, and they are reasonable to adopt. They are not a substitute for identifying a specific treatable condition, and should not delay one.

The male side of this topic gets less attention, and it has one finding that is genuinely part of a standard semen analysis.

Leukocytospermia.

Raised white blood cells in semen, conventionally above 1 million per milliliter. It is reported on a standard semen analysis, so no special panel is needed.

Why it matters:

• White cells generate reactive oxygen species, which damage sperm membranes and fragment sperm DNA
• It may indicate infection or inflammation of the prostate, seminal vesicles or epididymis
• It can coexist with normal-looking counts and motility while still affecting DNA integrity

Its interpretation is less straightforward than it appears. Round cells in semen include immature germ cells as well as white cells, and distinguishing them requires specific staining that is not always performed. A reported elevation is worth confirming before treating.

Where infection is confirmed, treatment is directed at the organism. Antibiotics given empirically for raised white cells without a confirmed infection have a weaker rationale and are not universally recommended.

Other male-side inflammatory considerations:

• Varicocele, which is associated with raised oxidative stress in semen
• Previous mumps orchitis after puberty
• Untreated sexually transmitted infection, which can cause obstruction as well as inflammation

• Recurrent Implantation Failure: What the 2023 Definition Changed
• Fertility Myths vs Facts: Ten Claims Checked Against the Evidence
• After a Failed IVF Cycle: What Is Worth Investigating
• Chronic Endometritis and IVF Failure
• What Is AMH and Why It Matters?
• Role of Probiotics in Women's Reproductive Health
• How Autoimmune Conditions Affect Fertility