The Semen Analysis

Most Important Measurements In The Semen Analysis

The semen analysis is considered the “workhorse” test to diagnosing male factor infertility. The test measures a number of parameters but clinicians typically focus on just a few:

  1. Concentration: The amount of sperm produced within a milliliter of semen.
  2. Volume: The number of milliliters of semen produced per sample.
  3. Count: The total amount of sperm produced in a sample (concentration x volume)
  4. Motility: The percentage of the sperm that can swim forward
  5. Morphology: The percentage of sperm that have the proper shape

If the answer to any one of these criteria is irregularly low, this will likely prompt another semen analysis test and then possibly any number of additional tests or treatments depending on the score and what kind of doctor is treating you.

As we discussed, reproductive endocrinologists and reproductive urologists will likely have differing reactions to the results of a semen analysis. As a result, it’s wise to get the perspective of both if the semen analysis looks abnormal.

Huge Variability

The field of reproductive urology has not agreed upon how to perform the semen analysis, how to interpret it, and how much to rely upon it. This is because the semen analysis suffers from two major weaknesses. First, one man can produce dramatically different samples, even just days apart. Second, the readings require a fair amount of judgement and, as a result, different labs will have different interpretations of the same sample. Below are two studies that nicely characterize how two samples from the same man can produce different readings (Keel) and how various laboratories can dramatically disagree about the same sample (Auger).

Amidst such variability, patients need to carefully select where they have their semen analysis performed and analyzed. The best study we can find, the Augur study referred to above, concluded that laboratories that have less experience and less training see a higher variance in their ability to count sperm (2.9 times more variance than experienced laboratories) and quantify motility (1.4 times more variance than experienced laboratories).

As a result, many reproductive urologists believe that having your semen analysis done at a fertility clinic, rather than at a normal hospital (or regular lab), will drive more accurate results. Because clinics often run 5 – 15 times the number of tests as a hospital and are often much more skilled at discovering if there is any rare sperm available in the sample (minimizing the risk of erroneously diagnosing azoospermia, covered in a future lesson).

The Process

There is sometimes disagreement about how many semen analysis tests are necessary. If the couple is having trouble conceiving, most reproductive urologists will want the man to have at least two tests, regardless of the results on the first. Other doctors will be happy with only one test if the results look normal.

Creating the proper conditions requires a few steps. First, most reproductive urologists insist the man ejaculates within five days of the test, but not within two days of the test. Below is a calendar representation of these windows. Getting this right is especially important to ensure the sample’s sperm concentration reflects what the man is capable of producing under optimized conditions.


Sample Calendar for semen analysis

Around the time of your semen analysis, your doctor will also likely allow you to consume alcohol and caffeine, provided it’s in moderation: as you will see in a few lessons, both can influence sperm quality when consumed above a certain level.

Once you provide a semen sample, it is analyzed within 60 minutes and a report is provided to your doctor. If the doctor requests a second test there is often a two week period between sample collections given the variability discussed above.

Reading The Semen Analysis

What we’re trying to establish with the semen analysis is whether or not the man can produce enough sperm that swim fast enough, and are of the right shape, for some of his sperm to fertilize an egg. As a result, we need to look at the concentration, motility, and morphology in conjunction with one another.

Unless the man is producing no sperm (known as azoospermia), below normal scores in any one category can often be compensated for by normal-ish scores in the other categories. For instance, if the man has a low percentage of motile sperm, but a large concentration of sperm, he may still produce enough motile sperm to fertilize an egg.

While having one below-normal parameter in the semen analysis is almost never a disqualifier for the man to conceive naturally, it certainly doesn’t help. Below you can see how men who have one below normal parameter are 2 - 3 times more likely to have fertility challenges, and when all three parameters are below normal, he is 16 times more likely to be infertile.

Sperm Concentration & Count

Sperm concentration is a function of how many sperm appear in each milliliter of semen the man produces. Sometimes doctors will multiply the man’s concentration by the total volume of semen produced in a sample (again, in milliliters) to calculate a total sperm count.

Oftentimes a doctor will want to see a concentration above 15 million per milliliter. However, and this is important to note, many men achieve pregnancy naturally with concentrations far below the averages.

Below is a histogram of sperm concentrations amongst roughly 700 fertile men and 700 men who cannot conceive naturally. As you can see, at high sperm concentrations, the majority of men are fertile. In the middle-ranges the proportions are more equal, and at low sperm concentrations it’s very possible the man can conceive naturally, but the odds are diminished.

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