Unexplained infertility: What it actually means, what the research says, and how diet and lifestyle may help

Hearing the words "unexplained infertility" can feel like being handed a locked door with no key. You have done the bloodwork, sat through the ultrasounds, waited on the semen analysis, and maybe even felt a flicker of relief when everything came back normal. Then comes the harder realization: if nothing is wrong, why are you still not pregnant?

If that is where you are right now, I want you to know two things from the start: you are not alone, and "unexplained" does not mean "nothing can be done." As a functional medicine dietitian, I meet many couples in exactly this moment, and I have seen how much steadier they feel once they understand what this diagnosis does and does not mean. Below, we will walk through what unexplained infertility actually means, what the research says, and how diet and lifestyle in both partners may support reproductive health while you and your care team keep looking for answers.

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Unexplained infertility is a diagnosis given when a couple has not conceived after 12 months of regular, unprotected intercourse (or 6 months if the woman is 35 or older), and a standard fertility evaluation of both partners does not identify a clear cause. It is a diagnosis of exclusion, which means it describes what standard testing did not find rather than proving nothing is there. Research suggests that nutrition, blood sugar balance, sleep, stress, and other lifestyle factors in both partners play a role in reproductive health, and these foundations can be supported alongside care from your fertility provider.

Key takeaways

• Unexplained infertility is common, accounting for as many as 30 percent of couples evaluated for infertility.

• "Normal" standard results do not always capture sperm DNA integrity, thyroid function, metabolic health, or nutrient status.

• The most consistent nutrition research points to a Mediterranean-style eating pattern and adequate nutrient status in both partners, though much of it is observational and some findings are mixed.

• Eggs and sperm develop over roughly three months, so consistent habits over a season matter more than any single change.

• Diet and lifestyle work best alongside medical care, not in place of it.

RELATED: WeNatal Guide for Trying to Conceive

What does unexplained infertility actually mean?

Unexplained infertility means you've been trying to get pregnant without success, but standard fertility testing hasn't identified a clear reason why. Your test results may look normal, yet pregnancy still isn't happening.

In the U.S., the American Society for Reproductive Medicine (ASRM) recommends seeking a fertility evaluation after:

• 12 months of trying if you're under age 35.

• 6 months of trying if you're 35 or older.

• Sooner if you're over 40 or have known fertility concerns.

A typical fertility evaluation looks at whether you're ovulating, whether your fallopian tubes are open, and whether your partner's sperm appears healthy. When these tests come back normal but you're still struggling to conceive, you may receive a diagnosis of unexplained infertility. In fact, up to 30% of couples experiencing infertility fall into this category.

But here's what's important to remember: Unexplained doesn't necessarily mean there's no reason. It simply means the testing done so far hasn't found one.

What does a standard fertility workup usually check?

Most standard evaluations look at the big structural and functional questions:

• Ovulation: whether it's happening regularly, often through cycle tracking and a mid-luteal progesterone level.

• Ovarian reserve: an estimate of remaining egg supply, usually through AMH and an antral follicle count.

• Fallopian tubes and uterus: whether the tubes are open and the uterine cavity looks healthy, assessed with imaging.

• Semen analysis: sperm count, motility (movement), and morphology (shape).

A normal result on each is genuinely good news. These tests are simply not designed to tell you everything about how eggs, sperm, and the body as a whole are functioning.

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Does "unexplained" mean nothing is wrong?

Not necessarily. Unexplained usually means that the cause was not found with the tests that were run, and some important factors sit outside a standard workup.

Sperm health is a clear example. A routine semen analysis looks at count, movement, and shape, but it does not measure the integrity of the genetic material inside the sperm. In one study of 119 men whose couples had been diagnosed with unexplained infertility, about one in four had an elevated sperm DNA fragmentation index despite conventional semen results that did not explain the couple's difficulty.

Fertility expert Aimee Raupp, MS, LAc, makes a point I return to often with clients: normal is not the same as optimal. A lab value can fall within a population reference range and still not reflect the internal environment where eggs and sperm develop. During our 2026 Reset panel on fertility, metabolism, and inflammation, fertility specialist Dr. Natalie Crawford noted that being told infertility is simply "bad luck" can leave people feeling powerless, when far more is within our influence than most people realize. The theme that stayed with me from that conversation is one I share with every couple: fertility is feedback, not failure.

What questions are worth bringing to your provider?

If you have been told everything looks normal, these are reasonable topics to discuss:

• Sperm DNA fragmentation testing for the male partner, especially after repeated unsuccessful cycles or pregnancy loss.

• A fuller thyroid picture, including free T4, free T3, and thyroid antibodies, not only TSH. 

• Metabolic markers such as fasting insulin and glucose, which can show how the body is handling blood sugar.

• Nutrient status, including vitamin D, ferritin (iron stores), B12, and folate.

• Inflammation markers such as hs-CRP.

Major guidelines do not recommend every one of these tests routinely, and the evidence behind each varies. That is exactly why they are best treated as a conversation with your provider about your own history, rather than a checklist to order all at once.

What does the research say about diet, lifestyle, and unexplained infertility?

Very few studies have looked at diet in couples with unexplained infertility specifically, so we lean on the broader body of fertility research. That research is encouraging but largely observational, which means it can show associations without proving cause and effect.

What we know

• Overall eating patterns matter. A review in the American Journal of Obstetrics and Gynecology found that diets favoring seafood, poultry, whole grains, fruits, and vegetables were related to better fertility in both women and men, and that supplemental folate was consistently associated with better fertility outcomes.

• Men's diets show up in sperm. A systematic review of observational studies found that diets rich in omega-3 fats, antioxidants, folate, and vitamin D, and lower in saturated and trans fats, were associated with better semen quality. Higher intake of alcohol, caffeine, and processed meat in men was associated with lower chances of pregnancy for their partners.

• Vitamin D status may play a role. A meta-analysis of 11 cohort studies including about 2,700 women undergoing assisted reproduction found that those with adequate vitamin D levels had higher live birth rates than those with deficient or insufficient levels.

How can diet and lifestyle support fertility when the cause is unexplained?

When there is no single cause to target, I shift the question from "what is broken?" to "what kind of internal environment are eggs and sperm developing in?" Both eggs and sperm mature over a window of roughly three months, so I encourage couples to think in seasons rather than single cycles. Here is where I usually start.

Build a Mediterranean-style plate

The goal is variety and nourishment, not restriction. Fill your plate with vegetables, fruits, legumes, and whole grains for fiber and polyphenols, enjoy low-mercury fish like salmon or sardines about twice a week, use olive oil, nuts, and seeds as everyday fats, and include protein at every meal. 

Keep blood sugar steady and ease the inflammatory load

Blood sugar, insulin, and inflammation are closely tied to hormone signaling in both partners, and chronic low-grade inflammation is one of the threads I look for most often when testing looks normal. Pairing carbohydrates with protein, fat, or fiber, eating regular meals, walking after eating, and choosing omega-3 rich foods and colorful plants over frequent ultra-processed foods and alcohol all help nourish steadier energy and a balanced inflammatory response. 

Close common nutrient gaps

Even with a thoughtful diet, gaps are common. For women, folate (ideally methylated), vitamin D, iron, choline, and omega-3 DHA are key preconception nutrients. For men, zinc, selenium, folate, vitamin D, and antioxidants such as vitamin C, vitamin E, and CoQ10 play roles in normal sperm development. Testing levels like vitamin D and ferritin helps you supplement with purpose.

Protect sleep, manage stress, and move with intention

• Sleep: Aim for seven to nine hours on a consistent schedule, ideally as a team. 

• Stress: You cannot remove every stressor, but you can give your nervous system daily chances to settle through a walk, breathwork, or meditation. 

• Movement: Regular movement, including strength training a few times a week, supports insulin sensitivity and metabolic health.

• Environment: Simple swaps, like not heating food in plastic and choosing fragrance-free products, can reduce exposure to endocrine-disrupting chemicals.

• Nicotine: If either partner smokes or vapes, getting support to quit is one of the most meaningful steps for reproductive health.

Your emotional health deserves care too. Unexplained infertility can be uniquely isolating, and prioritizing your mental health during your fertility journey is part of the plan, not a distraction from it.

RELATED: Men's health and sperm quality: Our panel with two fertility experts

What should both partners know about unexplained infertility?

Male factors are estimated to contribute to about half of all infertility cases, so unexplained infertility is never a one-partner question. Sperm are produced continuously, which means the next few months are a meaningful window for the male partner to support sperm health through food, sleep, movement, and fewer exposures like heat, alcohol, and nicotine.

In our men's health and sperm quality panel, reproductive urologists Dr. Justin Houman and Dr. Ariel Moradzadeh explain what a semen analysis reveals, what it misses, and the everyday habits that matter. 

A few simple ways to approach this together:

• Make diet and lifestyle changes as a couple so no one carries the work alone.

• Ask about male testing, including DNA fragmentation, early rather than late.

• Share appointments, results, and feelings openly. 

When should you talk to your provider?

Reach out to a fertility specialist if you have been trying for 12 months and the female partner is under 35, or for 6 months if she is 35 or older. It is worth seeking guidance sooner if you notice:

• Irregular, very painful, or absent periods

• A history of pregnancy loss

• Known concerns about sperm health, past testicular surgery, or erectile or ejaculatory changes

• A thyroid condition, autoimmune condition, or other chronic health issue

• Feelings of anxiety or low mood that are weighing on daily life

Medical guidelines for unexplained infertility generally recommend a stepwise approach, often starting with ovarian stimulation and intrauterine insemination (IUI) and moving to IVF when needed. Nutrition and lifestyle can support your body throughout that process. 

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Frequently asked questions about unexplained infertility

What is the most common cause of unexplained infertility?

By definition, unexplained infertility has no single identified cause. It often reflects subtle factors that standard testing does not capture, such as sperm DNA integrity, egg quality, the early steps of fertilization and implantation, or metabolic and inflammatory factors in either partner.

Can you get pregnant naturally with unexplained infertility?

Yes, many couples with unexplained infertility do conceive, sometimes without treatment. Your chances depend on factors like age and how long you have been trying, so your provider can help you decide how long to keep trying on your own and when to consider options such as IUI or IVF.

Can diet make a difference with unexplained infertility?

Nutrition plays a role in reproductive health for both partners. Research associates Mediterranean-style eating patterns, adequate folate and vitamin D, and diets lower in processed foods with better fertility markers, though much of the evidence is observational. Diet is one supportive part of a larger picture, not a guarantee or a treatment.

Should men be tested if infertility is unexplained?

Yes. A semen analysis is part of every standard evaluation, and because male factors contribute to about half of infertility cases, some couples benefit from asking about additional testing such as sperm DNA fragmentation.

Are supplements helpful for couples with unexplained infertility?

No supplement treats infertility, explained or unexplained. A high-quality prenatal for each partner can help fill common nutrient gaps that support normal egg and sperm development, and research on targeted supplements like antioxidants is mixed. Talk with your provider about which supplements make sense for you, especially if you are undergoing fertility treatment.

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A note from WeNatal on unexplained infertility

At WeNatal, we know how heavy the word "unexplained" can feel, and how easily it can leave couples wondering whether their bodies are working against them. We see it differently. Fertility is a shared, whole-body story shaped by nutrition, sleep, stress, metabolic health, and the daily habits of both partners, and the months before conception are a window of opportunity, not a test you can fail.

If you are looking for a place to start, our free fertility guide walks you through preconception nutrition and lifestyle for both partners. From there, WeNatal Together was created so couples can build their foundation side by side, pairing WeNatal For Her, with methylated folate, choline, iron, and vitamin D, and WeNatal For Him, with nutrients like zinc, selenium, and antioxidants that support healthy sperm development. For couples who want to round out their routine, Omega DHA+ provides omega-3s to support whole-body and reproductive health, and Egg Quality+ offers targeted support for egg cell energy with CoQ10.

Our supplements are designed to help fill nutrient gaps as one part of a nourishing routine. They are not a treatment for infertility, and they work best alongside a balanced diet, healthy habits, and guidance from your healthcare provider.

Wherever you are in your journey, support, not perfection, is the goal, and you do not have to do this by yourselves.

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