Understanding the Diagnosis of Unexplained Infertility

Negative pregnancy test

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Unexplained infertility is a frustrating diagnosis to receive. It is also a common one. Unexplained infertility does not, however, mean that you have no options. There is a reason for hope.

In fact, depending on your age and how long you've been trying, the odds of conceiving on your own may be higher than it is for most infertility diagnoses. A 2012 study of just over 1,300 women with infertility, ages 28 to 36, found that 43% of those who never received fertility treatment eventually conceived and gave birth. Here’s what your unexplained infertility diagnosis means, what it doesn’t, and possible explanations for the unexplained.

Unexplained Infertility 

Unexplained infertility is a controversial diagnosis. By definition, it’s a diagnosis of elimination. Your healthcare provider has determined you do not have this, this, and this problem, and yet, you’re not able to conceive. Approximately one in four fertility challenged couples will be told there is no explanation for why they can’t conceive. 

Unexplained infertility can only truly be diagnosed after a full and complete fertility evaluation of both the male and female partner. An unexplained infertility diagnosis may be justified if it has been shown that:

If any of the above has not been evaluated, a diagnosis of unexplained infertility may be premature. Some may also argue a laparoscopy is also needed to rule out endometriosis. Endometriosis cannot be diagnosed with blood work or ultrasound. That said, unless you’re experiencing painful periods, your doctor may not consider the risk of the surgical laparoscopy worth making a diagnosis. (More on endometriosis as a reason for unexplained infertility below.)

Unexplained vs. Idiopathic Female or Male Infertility

It’s important to clarify that unexplained infertility is not the same as idiopathic female or male infertility. Idiopathic means unexplained. But when a doctor talks about idiopathic male infertility, for example, they have already determined the man is infertile. His semen analysis results were not normal.

Why are the semen analysis results not normal? That may not be known. If the doctor can’t determine the cause, they may say he has idiopathic male infertility. Idiopathic female infertility may occur when a woman isn’t ovulating regularly or normally, but it’s unclear why ovulation isn’t happening when it should.

In both of the examples above, it’s known why the couple can’t conceive—she isn’t ovulating, or his semen isn’t in the fertile range. With unexplained infertility, the eggs are coming, the sperm are fine, but the couple still isn’t getting pregnant.

Possible Explanations

Unexplained infertility isn’t a magical condition. There is a reason; we just don’t know what it is. There are things we know may cause problems, but don’t have a way to measure or evaluate yet. (Or the only way is invasive and expensive, more on that below.) There are a variety of possible explanations for unexplained infertility.

Undiagnosed Underlying Condition

You may have an undiagnosed underlying (non-reproductive) medical condition. We don’t completely understand how poor health impacts fertility in more subtle, not yet measurable ways. But we are learning more and more. For example, untreated Celiac disease may in some cases of unexplained infertility.

A 2016 reanalysis of previous research studies have found that Celiac disease may be diagnosed about six times more frequently in women with unexplained infertility compared to the general public. The study authors noted, however, that previous studies were small so it's hard to know exactly how accurate those odds are. In addition, it also appeared that women with any type of infertility were more likely to be diagnosed with celiac disease.

Other underlying conditions that may cause infertility include diabetes, an undiagnosed thyroid disorder, and some autoimmune illnesses.

Mild Endometriosis

Severe endometriosis is more likely to cause fertility problems that are noticeable even without laparoscopy. For example, endometrial cysts may interfere with ovulation or even cause fallopian tube blockages.

Mild endometriosis may not interfere with ovulation or clear passage of the egg. It may also have no obvious symptoms. Endometriosis might be behind some unexplained infertility cases. However, experts don’t agree on whether mild endometriosis can cause infertility, and if yes, whether laparoscopic surgery for diagnosis and reprove endometrial deposits is beneficial.

The Vaginal Environment and Sperm

After ejaculation, sperm must make their way out of the semen and into the cervical mucus. Then, they must swim up from the vagina, into the cervical opening, and eventually into the uterus. Sometimes, there may be problems during that transition period, from the semen, into the cervical mucus, and up the cervix. For example, there may be antibodies in the cervical mucus or even the semen that attack the sperm.

This is known as hostile cervical mucus. How to effectively diagnose this problem isn’t clear, leaving cases like these frequently unexplained.

Poor Egg Quality

We have tests to determine if you’re ovulating, and testing to get a general idea of whether there is a relatively good quantity of eggs in the ovaries. But there is no test to determine whether the eggs are good quality. Poor quality eggs may be caused by age, an underlying medical condition, or some yet unknown cause. Poor egg quality may be diagnosed during IVF treatment. After egg retrieval, eggs will be examined under a microscope.

Poor Sperm Quality

Some kinds of poor sperm quality are recognizable. For example, poor sperm shape (also known as morphology) may cause fertility problems. Poor sperm motility (or movement) may also cause infertility. But these are diagnosable. They can be seen during a semen analysis. There may be issues related to sperm quality that are not obvious during semen analysis.

For example, the sperm may have poorer quality DNA. These DNA issues increase as a man ages, which is why children of older fathers are at an increased risk for certain birth disorders and mental health problems. Poor sperm quality may be diagnosed during IVF treatment. If good-looking sperm can’t seem to fertilize healthy looking eggs, this may indicate problems with egg or sperm quality.

Problems With the Endometrium

You can have a healthy cervical environment, healthy eggs, and healthy sperm…but if the resulting healthy embryo can’t impact into the endometrium, we have a problem. There is so much unknown about possible fertility problems related to the endometrium.

For example, one study published in 2016 found that a newly discovered virus is more commonly found in the endometrial tissue of women with infertility than in women with proven fertility. But how to diagnosis and treat this problem isn’t known. Luteal phase defects also fit under possible problems with the endometrium and could be the answer for some cases of unexplained infertility.

Problems With a Fertilized Egg

Let’s say we get a healthy looking egg and sperm, and they become an embryo. Next, the cells inside the embryo divide and grow to eventually form a fetus. Sometimes, this goes wrong. This is another problem that may be diagnosed during IVF treatment since embryos are monitored for normal cell division.

Unknown Factors

Some factor yet unknown to fertility experts: It may be that the cause of your unexplained infertility is completely unknown to medical professionals at this time. We don’t know everything there is about fertility yet.

Nothing May Be Wrong

Some couples with unexplained infertility will conceive without any treatment help within one to two years of diagnosis. No one knows why or what was wrong, but it happens. A healthy, fertile couple has about a 30% chance of conceiving in any given month. Notice that the odds are not 100%. They aren’t 100% for anyone.

It could be you have a very subtle fertility problem, but not so much that you can’t conceive on your own with more time. (This is sometimes called subfertility.) It could be you and your partner have had seriously bad luck. It’s frustrating, but it’s a possible explanation for those that have been trying to conceive for less than two to three years.

A Word From Verywell

Just as important as discussing what unexplained infertility is, it’s important to talk about what it’s not. It's not a non-issue, caused by you “trying too hard” or “stress," or just “in your head.” Some people, including some insensitive doctors, to dismiss infertility if a clear problem can’t be found. Your emotional struggle to conceive is just as real even without a definitive diagnosis. Some might say it’s more intense, because, without answers, you may feel more confused by the situation. 

Your possible physical problem is also just as real, even if it can’t or hasn’t been diagnosed yet. You want to get pregnant, and you can’t. That’s all worthy of attention and concern. If your doctor diagnoses you with unexplained infertility and tells you that "you just need more time," you may also want to consider a second opinion. While this true for some couples, and can be good advice in some situations, it's not so for everyone. It's worthy of follow-up.

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Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Rachel Gurevich, RN
Rachel Gurevich is a fertility advocate, author, and recipient of The Hope Award for Achievement, from Resolve: The National Infertility Association. She is a professional member of the Association of Health Care Journalists and has been writing about women’s health since 2001. Rachel uses her own experiences with infertility to write compassionate, practical, and supportive articles.