Semen Analysis Explained

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Guest Blogger, Christina Barnes, explains the importance of semen analysis and what it means for you and your growing family

If you’ve heard the term “semen analysis,” you might correctly assume that this is a test that evaluates an individual’s semen. Your doctors may tell you that a semen analysis can help pinpoint any causes of male infertility and that having one done is a key step in understanding and treating male fertility issues. This is all good to know, but what exactly is a semen analysis? The semen analysis looks at many different characteristics of the sperm and semen sample, with normal reference ranges from the World Health Organization (WHO) listed below. These reference ranges are helpful when comparing results to what is normal, but what exactly does this “normal” number mean? What are all of the different parts of semen that need to be analyzed? What is viscosity, and why is it better for this value to be lower? What is the difference between total sperm number and concentration of sperm? What are round cells, and why do these matter? 

If you’ve ever asked yourself these questions while trying to read through your semen analysis results, or if you haven’t had one done but want to know what it’s all about, then this article is for you. We’ll go through each of the categories of a semen analysis and talk about what it is, why it’s important, and what those normal values mean. 

Semen Analysis: WHO Normal Reference Ranges

Specimen Volume            ≥ 1.5 ml (milliliter)

Concentration               ≥ 15 M/ml (million per milliliter)

Total Sperm Number          ≥ 39 M/ejaculate            

Initial Motility                ≥ 40%

Initial Grade                ≥ 2.5

Viscosity                   < 2 (1 = Low, 4 = High)

Round Cells                < 5 per HPF (High Powered Field)

Morphology                 ≥ 4 % Normal Forms 

Specimen Volume

Specimen volume is the total amount of ejaculate that a man produces with one emission. The ejaculate contains sperm in addition to other fluids created by the male reproductive organs. These additional fluids act as a carrier for the sperm, helping them to swim and move towards their intended target. 

The normal volume for the total amount of ejaculate, including both sperm and non-sperm fluids, is equal to or greater than 1.5 milliliters (mL). For reference, one teaspoon is equal to 5 mL. So if a man has an orgasm and produces 2 mL of ejaculate, he would be producing a normal specimen volume. 

If a man produces a high specimen volume, does that automatically mean that he produces a large amount of sperm? Not necessarily. The number for the specimen volume does not take into account the amount of sperm versus the number of other fluids in the ejaculate; the specimen volume only looks at the total of both parts. In order to determine if the number of sperm in a sample is adequate, you have to look at concentration and total sperm number in the sample.

Concentration

The normal concentration of sperm in a sample is greater than or equal to 15 million sperm per 1 mL of ejaculate. This means that for every 1 mL of ejaculate, you ideally want to see at least 15 million sperm present. Remember that ejaculate is composed of both sperm and other non-sperm fluids produced by the male reproductive organs. 

An individual can have a high specimen volume, such as 3 or 4 mL of ejaculate, but still have a low concentration of sperm. If that individual has 4 mL of ejaculate but only 9 million sperm per mL of ejaculate, this would be a low concentration of sperm. Knowing the amount of ejaculate alone will not give you the concentration number. A large amount of ejaculate does not necessarily mean a high concentration of sperm. 

Individuals can have low sperm concentration in the ejaculate due to retrograde ejaculation, absence of the vas deferens, or other issues that cause obstruction in the body parts that carry the sperm through the reproductive organs. Think of the concentration of ejaculate as consisting of two parts: sperm and other bodily fluids. If anything gets in the way of the sperm being able to mix with the other body fluids, the concentration of the sperm in those body fluids will be low.  

Total Sperm Number

Total sperm number is as simple as it sounds: the total number of sperm in one total ejaculation. This number is calculated by counting all of the sperm in a sample, regardless of sample size. The normal number for total sperm count is greater than or equal to 39 million sperm per ejaculate. 

Initial Motility

Initial motility looks at the percentage of sperm in a sample that is motile, or capable of motion. Ideally, an individual would want greater than or equal to 40% of the sperm in the sample to be in motion. 

There are two types of sperm motility: progressive and non-progressive. Progressive motility is when the sperm makes active progress in its movement, either in a straight line or a circle. The sperm is capable of moving from one point to another, regardless of speed. Non-progressive motility is when the sperm is moving, but not able to travel in a way that makes progress from one point to another. A non-progressive sperm could be moving its tail but unable to swim. 

When examining a semen sample, the technician will generally calculate total motility, which is progressive and non-progressive motility together. They will also look at the percentage of only progressively motile sperm. Higher progressive motility rates are related to higher rates of pregnancy. 

Initial Grade

           Sperm are categorized into four different “grades” based on motility:

• Grade 1: Immotile: do not move at all
• Grade 2: Non-progressive motility: moving, but unable to make progress in any direction
• Grade 3: Non-linear motility: able to move forward, but does not travel in a straight line
• Grade 4: Progressive motility: travel in a straight line

Viscosity

Viscosity is a measure of the semen’s resistance to flow; the thicker the semen, the less likely it will be to flow. Maple syrup, for example, has a higher viscosity than water. Semen viscosity is graded on a scale of 1 to 4, with 1 being the least viscous (thinner) and 4 being the most viscous (thicker). A normal level of viscosity is less than 2. Semen that is too thick may impair the sperm’s ability to move. 

Round Cells

Round cells are cells in the semen sample that are not sperm: for example, round cells can be skin cells, white blood cells, and individual sperm heads or tails. The presence of round cells may indicate an underlying problem, such as inflammation of the accessory glands or testicular damage. The fewer round cells in a sample, the better. 

Morphology

Sperm morphology refers to the physical form of the sperm; in other words, the size and shape of the sperm. When studying the sperm morphology in a sample, the technician looks at the size, shape, and any physical defects of the sperm under a microscope. Sperm can have defects of the head, midpiece, and/or tail. Examples of defects in sperm morphology include:

• A head that is too big, too small, too narrow, or too wide
• A neck that is bent, too thick, or too thin
• A tail that is too short, bent, or coiled

The percentages of normal and abnormal sperm cells in a sample are calculated. A normal, healthy sample has greater than or equal to 4% normal sperm cells; it would be expected to see more abnormal sperm than normal sperm.  

For more information on semen analysis, explore these resources:

What’s in the Numbers: Explaining the Post Thaw Motility and Total Motile Cells

What’s in the Shape: Sperm Morphology