Putting the Pieces Together

Your workup came back normal. The labs were within range. The HSG looked clear. The semen analysis was fine. Your reproductive endocrinologist sat across from you, used the word “unexplained,” and recommended that you try for another six months, or move to IUI, or jump to IVF. You left the appointment with a treatment plan but not really an answer. And something about it didn’t sit right.

You are not imagining the gap. In fact, the gap has a name in the research literature, and it is bigger than most patients are told.

What “unexplained” actually means

According to the American Society for Reproductive Medicine, up to 30 percent of couples who struggle to conceive are eventually diagnosed with unexplained infertility. Other experts put the number closer to 15 percent. The variance isn’t random. A 2024 systematic review published in BJOG found “substantial heterogeneity in the diagnostic criteria used to define unexplained infertility,” which is the polite scientific phrasing for: experts don’t agree on what counts as a complete workup.

That matters because “unexplained” doesn’t actually mean what most people assume it means. It doesn’t mean every possible factor has been investigated. It means the standard set of tests didn’t find anything. Those are two very different things, and the gap between them is where this article lives.

What a standard workup actually covers

The current ASRM committee opinion on fertility evaluation of infertile women lays out what most reproductive endocrinologists run as a baseline: a thorough medical history, a physical exam with a focus on the thyroid and pelvis, hormone tests (FSH, LH, estradiol, AMH, TSH, prolactin), assessment of ovulation, a hysterosalpingogram or other tubal patency test, an ultrasound of the reproductive organs, and a semen analysis for a male partner. ACOG and ASRM jointly recommend that this evaluation be expedited for women older than 35.

That panel is genuinely useful. It catches the things it was designed to catch. Anatomical issues, ovulatory problems, severe sperm abnormalities, low ovarian reserve, untreated hypothyroidism. If something on that list is the reason you’re not pregnant, the standard workup will probably find it.

What it won’t find is anything it wasn’t designed to look for.

The pieces that standard workups often skip

Here’s where the research literature has moved well past the standard panel without standard care necessarily catching up. None of what follows is fringe. Each of these is being studied seriously in mainstream reproductive medicine, and each has a real, documented relationship to fertility outcomes. They just don’t always make it into a basic workup.

Thyroid antibodies, not just TSH

Most standard panels include thyroid-stimulating hormone, or TSH. Fewer routinely include thyroid antibodies, the markers of thyroid autoimmunity (TAI). A 2022 review in Frontiers in Endocrinology concluded that increasing evidence confirms the association between thyroid autoimmunity and the risk of pregnancy loss, and suggests its relationship with reduced fertility. A recent prospective cohort study of women with unexplained recurrent pregnancy loss found that TAI was independently associated with increased risks of subsequent pregnancy loss, hypothyroidism during pregnancy, premature rupture of membranes, and preterm birth.

There is also conflicting evidence: one large study of healthy fecund women found that TSH levels above 2.5 mIU/L or the presence of antithyroid antibodies were not associated with fecundity, pregnancy loss, or live birth. So this isn’t a settled story. But if it’s never tested, it can’t be part of the conversation.

Sperm DNA fragmentation

A standard semen analysis measures count, motility, and morphology. It does not measure the integrity of the DNA inside the sperm. That’s a separate test, and it’s genuinely contested in mainstream care. A 2023 review summarized the state of the evidence: sperm DNA fragmentation has been associated with reduced fertilization rates, lower embryo quality, lower pregnancy rates, and increased miscarriage rates. But the same review noted that there is still insufficient evidence to recommend routine use in everyone, due to differences in testing methods, the absence of standardized cutoff values, and a shortage of randomized trials.

Where it tends to be most useful: cases of recurrent miscarriage, unexplained infertility, recurrent IVF failure, or where the male partner has lifestyle or environmental risk factors. It is rarely run as part of a first-line workup.

Endometrial receptivity and the uterine microbiome

Even with a high-quality embryo and a healthy-looking uterus, implantation can fail. Two newer areas of research have started to ask why.

The endometrial receptivity array, or ERA test, attempts to identify a personal “window of implantation” by analyzing gene expression in a uterine lining biopsy. The evidence on it is mixed. Recent systematic reviews have concluded that for most patients with a favorable prognosis, the ERA does not significantly improve pregnancy outcomes. But the same body of research suggests potential benefit, sometimes a roughly 20 percent improvement, in women with documented recurrent implantation failure.

Separately, the endometrial microbiome, the community of bacteria living in the uterine lining, has emerged as a real factor in implantation. A growing literature shows that a Lactobacillus-dominant endometrium is associated with higher implantation rates, while dysbiosis (a low Lactobacillus ratio with an overgrowth of other species) is associated with recurrent implantation failure and pregnancy loss. This is rarely tested unless a patient asks about it or has already had multiple failed cycles.

Metabolic and insulin function

Insulin resistance is often associated with PCOS, but the research has expanded well beyond that. A 2024 review in Frontiers in Endocrinology summarized how insulin resistance affects female reproductive function: it can activate oxidative stress, interfere with energy metabolism, affect oocyte development and embryo quality, change endometrial receptivity, and reduce assisted reproductive technology outcomes. A separate study published in 2017 found increased insulin resistance specifically in men with unexplained infertility.

A standard fertility panel doesn’t usually look at fasting insulin, HOMA-IR, or a comprehensive metabolic profile unless a patient has obvious PCOS markers. For a lot of patients with metabolic dysfunction that hasn’t yet crossed into a diagnosis, the question never gets asked.

Reproductive immunology

Implantation depends on a careful immune balance. The maternal immune system has to tolerate an embryo that is genetically half foreign, while still functioning normally against actual threats. When that balance is off, reproduction suffers. Recent reviews have explored the role of natural killer cells, CD138+ plasma cells, KIR receptors, and chronic endometritis in idiopathic infertility and recurrent miscarriage.

Reproductive immunology is still a contested specialty. Some treatments offered in this space have weak evidence and high cost. But the underlying science is real, and for patients with otherwise unexplained recurrent miscarriage or implantation failure, asking about an immune workup is reasonable. It is rarely a first-line investigation.

Sleep and circadian rhythm

Sleep is almost never part of a fertility evaluation, and the data suggests maybe it should be. Research summarized in Current Sleep Medicine Reports has linked sleep disturbances in women to menstrual irregularities, reduced conception rates, and miscarriages. A large cohort study found that irregular sleep patterns were associated with a decline in the probability of conception, while regular sleep-wake cycles with longer duration and perceived sufficiency were positively associated with fecundability. Both short sleep (under seven hours) and long sleep (over nine) have been linked to reduced fertility in men and women.

Sleep apnea, in particular, is dramatically underdiagnosed in women and is associated with reproductive hormone disruption. If you snore, wake unrefreshed, have unexplained daytime fatigue, or have a partner who reports breathing pauses, this is worth bringing up.

Autonomic function

This week’s other feature went deep on this one, so it gets a short paragraph here: heart rate variability, as a window into autonomic nervous system function, is an emerging fertility-relevant signal, especially for cycle regulation, IVF outcomes, and conditions like endometriosis and recurrent pregnancy loss. Like the other items in this list, it doesn’t show up in a routine workup. Like the other items in this list, it can be worth asking about.

Myth: An “unexplained” diagnosis means everything has been ruled out.

Reality: An “unexplained” diagnosis means the standard panel didn’t find anything. The standard panel is intentionally focused on the highest-yield, most evidence-backed factors. Many of the items above were not part of it.

Why standard care stops where it stops

It’s worth being honest about why a standard workup is what it is. Reproductive endocrinologists are not withholding good tests for sport. The standard panel reflects a set of real constraints.

First, evidence thresholds. Mainstream medicine adopts new tests once they meet a bar of randomized-trial evidence and clinical consensus. Many of the items in the previous section are well-studied but haven’t crossed that bar yet (sperm DNA fragmentation and ERA are the clearest examples). Second, insurance coverage. A test that isn’t standard is often a test that won’t be reimbursed, which puts the cost on the patient and the documentation burden on the practice. Third, time. A typical RE consult is short, and ordering ten extra labs requires both clinical justification and follow-up bandwidth that the system isn’t built for. Fourth, training. The specialty is enormous, and not every clinician follows every emerging area. Reproductive immunology, for example, sits at a contested edge of the field where reasonable specialists disagree.

None of these are bad-faith reasons. But they are reasons that have very little to do with whether a particular test could be useful for you, specifically. That’s the gap the next section is about closing.

How to bring it up with your doctor

Patient self-advocacy is not about catching your doctor in a mistake. It is about helping them make decisions with more of your information in front of them. Done well, it makes you a better patient, not a difficult one. A few principles that tend to land well.

Frame it as a conversation, not a challenge. “I’ve been reading about [test or factor]. I’d love to understand whether it would change anything in my case” lands very differently than “Why haven’t you run [test]?” The first opens a discussion; the second often closes one.

Tie your ask to your specific situation. Doctors weigh tests against patient histories. “Given that I’ve had two failed transfers and we still don’t have an explanation, would [endometrial receptivity / DNA fragmentation / immune workup] make sense at this point?” will land better than a generic request for more testing.

Ask for the reasoning, not just the yes or no. If a test is declined, ask what would have to change for it to be considered. That gives you a roadmap, and it tells you whether the answer is “there’s no evidence yet” (a clinical judgment) or “insurance won’t cover it” (a practical one) or “we don’t order that here” (which may be a sign to seek a clinic that does).

Know when a second opinion makes sense. Multiple failed cycles, recurrent miscarriage, an “unexplained” diagnosis after limited workup, or any moment when your clinic stops being curious about your case are all reasonable triggers for a second opinion. ASRM maintains a clinic directory, and many patients have found it useful to consult a clinic with a reproductive immunology or recurrent loss specialty in addition to their primary REI.

Consider whether an integrative or functional fertility specialist could help. This is a vetting exercise. Some integrative practitioners are excellent and order labs your REI doesn’t (full thyroid panels, fasting insulin, vitamin and mineral status, comprehensive stool analysis). Others run expensive tests with little evidence. Look for someone with real reproductive credentials, clear pricing, and a willingness to coordinate with your primary fertility team rather than replacing them

A workup that catches up

The standard fertility workup of 2026 doesn’t look exactly like the standard workup of 2015, and it won’t look exactly like the standard workup of 2030. The field moves. Tests that are considered “not yet routine” today end up in guidelines a decade later, usually because patients asked about them, because researchers kept publishing on them, and because enough clinicians decided the bar of evidence had been met.

That movement isn’t passive. A lot of it happens in exam rooms, when patients show up with a specific question and a clinician decides it’s worth running the test. Your appointment is one of those rooms. You don’t have to have memorized every study or know every term to walk in with the right posture. You just have to know that “unexplained” is not the end of the conversation. It is, often, the place where the real conversation starts.

The pieces of your fertility story may not all be on the standard panel. That doesn’t mean the pieces aren’t there. It means they’re waiting to be put together.