Microbiome and Fertility: The Role of the Gut in Reproductive Health

For years, talking about fertility meant talking about ovaries, uterus, tubes, and sperm. Research over the past decade showed that reproductive health depends on considerably more than the organs directly involved.

Today we know that metabolism, the immune system, hormonal balance, and even gut health influence how the body works. In that context, one topic drew a great deal of interest: the microbiome.

This is a field still under construction, and that is worth saying up front. Even so, the available evidence already reveals connections worth understanding.

What the microbiome is

The microbiome is the collection of millions of microorganisms, mostly bacteria, that naturally live in the gut, skin, mouth, and reproductive tract.

Far from being a problem, many of those bacteria carry out essential functions:

• They take part in digesting food
• They support nutrient absorption
• They contribute to immune system function
• They help produce certain vitamins
• They maintain the balance of several metabolic processes

The greatest concentration is in the gut, which is why people speak of the gut microbiome.

When the balance among bacterial species is right, the body works more efficiently. When that balance breaks down, a phenomenon called dysbiosis, changes appear that reach different systems in the body.

What the gut has to do with fertility

The gut and the reproductive tract look like separate worlds. What connects them is that both maintain constant communication with the rest of the body.

The microbiome takes part in processes involving:

• Immune system regulation
• Metabolism
• Inflammation
• Production and metabolism of certain hormones

All of these carry weight in reproductive health. Current evidence suggests that an imbalance in the microbiome could be associated with metabolic, inflammatory, and hormonal changes that indirectly influence fertility.

To be precise: this does not make the microbiome a cause of infertility. It places it within the set of factors that help understand how the body works as a whole.

The estrobolome: the most studied piece

The most researched part of this relationship is how the gut microbiome participates in estrogen metabolism.

There is a group of bacterial genes researchers call the estrobolome that takes part in how the body processes these hormones. Certain gut bacteria can cause some estrogens to be reabsorbed rather than eliminated.

When bacterial balance is right, that mechanism runs in a more orderly way. When it is disrupted, some of those processes change. Researchers continue studying how those changes relate to different gynecological and reproductive conditions, endometriosis among them.

Immune system, inflammation, and fertility

Around 70% of immune system cells are associated with the gut. That makes the microbiome a key piece in the communication between beneficial bacteria and the body’s defenses.

With the right balance, the immune system responds in a more controlled way. Several studies observed that dysbiosis can promote low-grade inflammatory states that affect various functions.

Chronic inflammation is today one of the most researched topics in metabolic and reproductive medicine, precisely because of its possible role in processes related to fertility.

Metabolic health enters the equation

Reproductive medicine has been demonstrating that fertility is closely linked to metabolism. Conditions such as insulin resistance, excess weight, metabolic syndrome, or altered glucose metabolism are also associated with changes in the gut microbiome.

That is why many specialists consider that understanding metabolic status allows for a considerably more complete assessment of reproductive health.

If you want to go deeper into that link, we cover it here: Insulin Resistance and Fertility: The Metabolic Link Many Couples Don’t Know About.

Reproductive health depends on systems that communicate with each other

Does it influence male fertility too?

Yes. Although early research focused on women’s health, how the microbiome relates to male fertility is now being studied as well.

Some studies explored its possible link with sperm quality, sperm motility, inflammatory processes, and oxidative stress. More research is still needed, but the finding reinforces something already taking hold: male fertility is also better understood from a comprehensive perspective.

We wrote about this recently: Male Fertility in 2026: Why Sperm Alterations Are on the Rise.

What about the vaginal microbiome?

Beyond the gut, there is also a vaginal microbiome, made up of microorganisms that help maintain the natural balance of the female reproductive tract.

Various studies showed that certain beneficial bacteria contribute to a healthy environment. Research continues exploring what role it plays across the different stages of reproduction. Many questions remain open, and it is another example of how reproductive health depends on interconnected factors.

Habits that support a balanced microbiome

There is no single formula. These habits do contribute to overall well-being:

Varied nutrition. Fruits, vegetables, legumes, whole grains, and fiber-rich foods provide the nutrients that support bacterial diversity. We cover it here: Nutrition and Fertility: What Really Matters and What’s Just a Myth.

Getting enough sleep. Rest takes part in metabolic and immune processes that influence gut balance.

Moving regularly. Moderate exercise is linked to metabolic benefits and overall well-being.

Managing stress. Chronic stress influences several body functions, including gut mechanisms.

Avoiding tobacco. Smoking has broad negative health effects and also disrupts microbiome balance.

All of this connects with a topic we covered last week: Epigenetics and Fertility, where we explain how habits modify the way your genes are expressed.

Do probiotics improve fertility?

Here it pays to be clear. Probiotics are live microorganisms that under certain circumstances offer health benefits, and there is growing scientific interest in their role in reproductive health.

That said: as of today there is not enough evidence to claim that probiotics, on their own, improve fertility or increase the chances of achieving a pregnancy.

Their use should be individualized and form part of guidance from a healthcare professional where appropriate. Be wary of any product promising otherwise.

Frequently asked questions

Should I get a microbiome test?

Microbiome tests exist, but their clinical usefulness in fertility is still being defined. Before investing in one, it is worth reviewing with your physician whether in your case it provides information that changes decisions.

Can I improve my microbiome through diet alone?

Nutrition is the most consistent lever available today. A varied, fiber-rich diet supports bacterial diversity, and that diversity is what is associated with better overall status.

If I have digestive problems, does that affect my fertility?

Not directly or automatically. What does happen is that persistent digestive conditions can come with inflammation or metabolic changes, and those are factors worth assessing within a comprehensive workup.

Does this replace fertility treatment?

No. Caring for your microbiome improves general conditions. If there is an underlying medical cause, it needs specific diagnosis and treatment.

At Ingenes, fertility goes well beyond the reproductive system

Every person is different, and fertility results from the interaction of biological, hormonal, metabolic, and lifestyle factors.

That is why we promote a comprehensive evaluation that makes it possible to understand reproductive health from a broader perspective, supported by precision diagnostics, highly specialized technology, and a multidisciplinary team.

Science keeps expanding what we know about the microbiome and its relationship with fertility. If you want to understand which factors are at play in your case, a First Consultation is the starting point.