Sperm Density, Sperm Motility, and Total Motile Sperm Count
Sperm Density
Sperm density is the number of sperm that are present per milliliter (cc) of semen. Sperm density is typically reported in units of millions of sperm per cc.
While the latest WHO criteria designate a normal sperm density as 15 × 106/cc or more, I think a sperm density of 40 × 106/cc or more may be more appropriate for a truly normal sperm density. However, using the total motile count (TMC) is arguably an even better way of judging male fertility potential.
A few commonly used terms regarding sperm density:
Oligospermia: any sperm density less than what is considered normal
Severe oligospermia: typically considered to be less than 5 million sperm/cc
Azoospermia: no sperm at all seen in the ejaculate
Virtual azoospermia: only a very small number of sperm (sometimes defined as less than
100,000 sperm/cc)
Of note, azoospermia and virtual azoospermia are explored in greater detail in separate sections of this website.
SPERM MOTILITY
Motility, or the number of sperm that are actually swimming, is important for success with natural intercourse and intrauterine insemination, because the sperm need to be able to swim up the fallopian tubes, where fertilization takes place. For IVF, sperm motility is not quite so important since sperm can be injected directly into an egg in the lab with the use of intracytoplasmic sperm injection, or ICSI. However, the sperm that are injected need to be alive, and motility is an accurate marker of this (i.e. if sperm are moving then they are live, although sperm that are not swimming may be alive as well). Decreased sperm motility is sometimes called “asthenospermia”.
IMPORTANT ASPECTS OF SPERM MOTILITY
TOTAL MOTILITY: the total percentage of sperm that are actively swimming (the latest WHO criteria define normal total motility as 40 percent or more)
MOTILITY GRADE: how well (on average) the sperm are swimming. There is significant variability in the reporting of motility grades between labs. The primary distinction to always keep in mind when evaluating motility grades is how many sperm have what is called “progressive” motility, meaning that they have good forward movement. Sperm that are moving but just twitching in place (not moving forward) are not going to be able to swim up the fallopian tubes to where egg fertilization takes place. The 5th edition WHO defines normal progressive motility as 32% or above. We will now describe some of the more common ways that labs denote progressive motility.
Method #1: Average grade of motility
Many labs describe the average grade of how all of the sperm are swimming. This does not really fit in with the WHO classification of percentage of sperm with progressive motility but provides the overall average of sperm. Although there is some variability between labs, degrees of motility are generally defined as:
1) No motility- this is usually defined as either Grade 0 (or Grade D)
2) Sluggish movement with absent or minimal forward progression- this is usually considered to be grade 1 or Grade C
3) Decent sperm activity with forward progression- this is called Grade 2 or Grade B
4) Very strong activity with forward progression- this is generally defined as Grade 3 or Grade A
The last 2 categories (grade 3/grade A and grade 4/grade B) are considered to be sperm with progressive motility. Sometimes grades are given as a range, for example: “Grade 1-2”. For these, essentially the grade would be considered 1.5. Normal average grade of motility is considered to be grade 2 or higher.
Of note, if a man has a motility grade of 1, this does not mean that all of his sperm have non-forward progression. There are still most likely a certain percentage of sperm present with better forward progression and which are capable of traveling up the fallopian tubes (unlike the majority of their fellow sperm in that particular sample).
Method #2- Describing the actual percentage of sperm with progressive motility.
As mentioned previously, the latest WHO criteria define normal progressive motility as 32% or higher. Many labs just provide this information on their reports. Other labs will list each of the 4 categories above (grade 0-3) and list the percentage of sperm that fall into each category (and you then need to do the math to figure out of if the ones with progressive motility add up to 32% or higher). For example:
25% Progressive motility (Grade 3)
15% Slowly progressive (Grade 2)
10% Twitching (Grade 1)
50% Non-motile (Grade 0)
So for this patient, the total motility would be 50 percent (those in grades 1, 2, or 3), while the progressive motility (grade 2 and 3 ) would be 40%.
SPERM AGGLUTINATION
One issue to consider regarding motility is the presence of anti-sperm antibodies (ASAs), which can cause sperm to stick together, thereby decreasing their motility. Most good fertility-specific labs will note on the semen analysis report if significant clumping (also called agglutination) of sperm is seen. Sperm clumping combined with poor motility is suggestive of the presence of ASAs; their presence can be confirmed on repeat semen analysis with direct (immunobead) ASA testing.
More detailed information on anti-sperm antibodies can be found in the above separate section on this website.
The Problem with Using the Standard Semen Parameters
Most physicians rely on sperm density and motility to determine the fertility potential of men. The problem with this approach is that when viewed in isolation, these parameters can provide an inaccurate picture of the actual number of swimming sperm. The reason is that the testicles provide only about 5 percent of the volume of ejaculate that is released during ejaculation. The other 95 percent of the fluid comes from the seminal vesicles and prostate gland, and their fluid production can vary from day to day and has nothing to do with testicular sperm production. In essence, the prostate and seminal vesicles provide the fluid “vehicle” for delivery of the sperm, while the testicles provide the sperm “content.” What determines the actual fertility potential of the semen is the total number of swimming sperm that are present in the entire ejaculate, not the amount of sperm present per unit of semen.
An analogy would be to try to judge how much blue dye is in two different amounts of water. Let’s say you added one cup of concentrated blue dye (representing the sperm) into a gallon of water (lower ejaculate volume) and another one cup into a whole bathtub of water (high ejaculate volume). The amount of dye present is the same in both amounts of water, but the density of dye in the bathtub is going to be significantly lower than in the gallon of water.
The same concept applies to semen. The testicles are adding a certain amount of sperm into the ejaculate, and this amount of sperm is what you are trying to measure. Meanwhile, the ejaculate volume is going to vary depending on the production of fluid by the seminal vesicles and prostate. We want to know the total number of swimming sperm present in the entire ejaculate and not just how concentrated or diluted the sperm is within the ejaculate fluid. The way to determine this total number of swimming sperm is to calculate the total motile count (TMC).
Total Motile Count (TMC)
The total motile count (TMC) gets around the problem of fluctuating ejaculate volumes by combining the sperm density, motility, and ejaculate volumes together to provide the total number of swimming sperm that are present in the entire ejaculate.
Some labs report this number under the label “TMC,” while others call it something slightly different, such as “total motile sperm,” “motile sperm count,” or some other similar variation. The key to identifying what the lab is talking about is the unit of measure, which should say “__ million” (or “__ × 106”) for TMC, as opposed to “__ million per cc” (or “__ × 106/cc”) for sperm density. The other differentiation that you need to keep in mind is the “total count,” which is the total number of both swimming and non-motile sperm (and is not as useful a number).
If the TMC is not reported, it can be easily calculated by using the following equation:
(Sperm Density × Ejaculate Volume × Total Motility) ÷ 100
For example, an analysis with an ejaculate volume of 2.0 cc with a sperm density of 30 × 106/cc and a total motility of 50 percent would have a TMC of (2.0 × 30 × 50) ÷ 100 = 30 million sperm.
WHAT IS A NORMAL TMC?
In terms of successfully establishing a pregnancy with natural intercourse or IUI, higher numbers of total swimming sperm are better. A TMC of 25 million sperm is getting into the territory of good fertility potential. Men with a TMC of 25 million or above were found to have a 6 times higher chance of successfully conceiving a pregnancy naturally when compared to men with a TMC below this level. [Ayala C. J Androl 1996].
There is some evidence that there may be some additional benefit to increasing levels of motile sperm when conceiving naturally up to a level of 75 million sperm (see below). A 2002 study looked at 940 couples who achieved pregnancy naturally and found a correlation between decreasing time to achieve pregnancy and rising sperm counts up to 55 × 106/cc. Above this level of sperm density there was no additional benefit in how quickly a pregnancy was established. [Slama R. HumReprod 2002] In this study, the average semen volume was 3.14 cc and the average motility was 61.4 percent. Plugging these figures into the equation for calculating TMC produces (3.14 × 40 × 61.4) ÷ 100 = 77 × 106 sperm. So there is some evidence that increasing TMC’s up to around the 75 million range may offer additional benefit for couples trying to conceive naturally.
Summary: Although these numbers are controversial and based on some fairly old studies, a TMC of 25 million or above seems to be a good goal for couples trying to conceive naturally, with some evidence of further benefit for TMC’s of up to 75 million sperm.
WHY CALCULATING TMC IS IMPORTANT
Consider a man who has a sperm density of 30 × 106/cc with an ejaculate volume of 1.1 cc and a total motility of 50 percent. His calculated TMC is 16.5 × 106.
Now, let’s take a second man who has a sperm count of only 6.6 × 106/cc and the same motility, 50 percent, but an ejaculate volume of 5.0 cc. His calculated TMC is the same: 16.5 × 106.
Both of these men have the same number of swimming sperm in their ejaculate. But if the standard WHO definitions are used, the first man would be considered well within the normal range (and would probably not get a recommendation to have a male fertility evaluation, even though he should), and the second man would be considered to have significantly abnormal semen parameters.
MOTILITY GRADE AND TMC
One very important consideration to keep in mind when evaluating TMC is the average motility grade. If most of the sperm are only twitching, then their fertility potential is not going to be very good for natural intercourse or IUI. Therefore, a TMC is considered “normal” only if the average motility grade is 2 or higher.
TOTAL PROGRESSIVE MOTILITY COUNT (TPMC)
Ok, so now that we have figured out TMC, the male fertility scientific community throws in another level of complexity. Instead of calculating the TMC and looking at the average grade of motility, some clinicians prefer to just calculate the total number of swimming sperm which are moving forward progressively. This does make sense in some ways, as this is the population of sperm which generally are going to be able to get to an egg and fertilize it. The calculation is just a little different:
(Sperm Density × Ejaculate Volume × Progressive Motility) ÷ 100
Again, the progressive motility is sometimes listed on the semen analysis report, and sometimes need to be calculated by adding the percentage of sperm with Grade 2/Grade B and Grade 3/Grade A motility.
The “normal” range for TPMC in terms of attempting natural conception has been determined to be 20 million sperm or above by some authors. [Hamilton JAM. HumReprod 2015]. However, it must be noted in this same study that men with very low TPMC’s (<1million) were able to establish a pregnancy up to 25% of the time over a 3 year time period, and that the chances of natural pregnancy were significantly higher when the TPMC was above 5 million sperm. The bottom line is that many couples are able to conceive with sperm counts below the normal TPMC range of 20 million, but higher numbers do increase the chances of success.
Which is better: TMC or TPMC?
I do not think that there is a definitive answer to that question. The TPMC is measuring the total number of sperm which are capable of getting to the egg in the female reproductive tract and this is good information. However, if the overall average sperm grade is taken into account when looking at the TMC, this can provide potentially valuable information as well. Generally, most people use whichever calculation they can do based upon the information provided to them on the semen analysis report. If the lab provides only the average grade of motility, then you have to use TMC. However, if a progressive motility is reported, then you are going to need to use TPMC. Both are perfectly valid, but you just need to understand the difference of what numbers you are looking at (TMC vs. TPMC) since normal values cut-offs for TMC are higher. Often, scientific papers on the topic often use the term “total motile count” to denote both TMC and TPMC, so you need to look into the “Material and Methods” section of the paper to see a description of how the numbers were calculated.
Clinical Impact of Using only Sperm Density and/or Motility in Isolation
As mentioned previously, the semen analysis test is best single predictor of male fertility potential that we currently have today. When utilized correctly, this information can provide important prognostic information on a couple’s chances of success, regardless of whether they are trying to conceive naturally, using IUI, or even IVF/ICSI.
However, sperm counts and motility can be used incorrectly. Just looking to see whether a man’s sperm density and motility are both in the “normal” range as defined by the WHO criteria may be a useful screening device by referring providers to see which men should be referred to a male fertility specialist for further evaluation. However, using these criteria by themselves are not very helpful in predicting if a couple is going to be successful conceiving naturally. This lack of correlation between standard WHO semen parameters and clinical outcomes has been a complaint of clinicians for decades. Multiple studies dating back to 1988 have found that relying just on the defined normal values of isolated parameters such as sperm density and motility as defined by the WHO were not very predictive of that couple’s chances of naturally establishing a pregnancy. [Polansky FF. Fert/Steril 1988] [Van der Steeg JW. FertSteril 2011] [Esteves SE. Urology 2012]
As described earlier, the calculation of the total motile sperm count provides a more accurate assessment of a man’s fertility potential by determining the total number of swimming sperm in the ejaculate. We will now look at the impact of TMC and TPMC on predicting the chances of successfully establishing a pregnancy using natural intercourse, IUI, and IVF.
IMPACT OF TMC AND TPMC ON FERTILITY OUTCOMES
Natural Intercourse
It makes logical sense that if a man has more and better swimming sperm, that his chances of conceiving a pregnancy naturally would be higher. Therefore, it has always been very frustrating for clinicians that the standard values for sperm density and motility were not particularly useful in counseling couples on their chances of establishing a pregnancy naturally. A 2015 study of 2,476 infertile couples fortunately found that calculating a man’s total progressive motility count (TPMC) seemed to solve these problems and much more accurately predict the chances of a spontaneous ongoing pregnancy. It found that men with a TPMC of <5 million sperm had a significantly lower chance of establishing a pregnancy naturally than a TPMC of 5 million or above. (Hamilton JAM. HR 2015]. Interestingly, even men with extremely low counts (TPMC <1 million) were able to establish a pregnancy naturally about 25% of the time within the 3-year study period. The ability of total motile counts to predict natural pregnancy was also shown by a study of 1,055 couples which again showed sperm density and motility by themselves did not correlate well with outcomes. However, if the sperm TMC was 25 million sperm or above, the chances of natural conception were 6.1 times higher than if the TMC was less than 25 million. [Ayala C. JAndrol 1996]. This cut-off closely follows the generally accepted definition of a normal TMC which is 20 million sperm or above.
Conclusion: Natural conception is possible at even very low sperm counts (TPMC <1million) and sperm count and motility by themselves are not good predictors of success. Increased TMCs are correlated with increased chances of success with natural intercourse. If a couple has been trying for at least a year and they have a TPMC/TMC of <20-25 million sperm, they may want to consider moving on to other treatment options such as IUI or IVF.
Intrauterine Uterine Insemination (IUI)
Like for natural intercourse, it intuitively makes sense that IUI success rates would be higher when more motile sperm are present in the ejaculate. Numerous studies have been reported over the years looking at IUI outcomes and how they correlated with a man’s TMC and TPMC. What each study has tried to evaluate is a cut-off point below which IUI is not worthwhile to try and the couple should just consider moving on to IVF.
Pre-Wash vs. Post-Wash: When an IUI is performed, the semen specimen needs to be “washed” in the lab in order to remove potentially detrimental substances (such as bacteria and white blood cells) that are normally screened out by the cervix during natural intercourse. The semen is also concentrated into a smaller volume and the lower quality sperm are selected out. During an IUI, the counts and motility are usually again evaluated after the wash. In general, sperm counts go down and percent motility goes up after a wash, since the sperm of lower quality (and lower motility) are removed. Studies have looked at whether post-wash vs. post wash motile counts are more accurate at predicting IUI outcomes.
Pre-Wash Total Motile Count (TMC)
Some studies have found that a cut-off for TMC of 5 million sperm or above is recommended for couples wanting to do IUI. [Dickey RP. FertSteril 1999] For example, a 2010 study of 353 couples found an overall clinical pregnancy rate per couple of 28.5% for IUI when the TMC was less than 5 million sperm, as opposed to 44.3% when the TMC was 5 million or above. [Merviel P. FertSteril 2010] However, other studies point to a higher recommended TMC cut-off of 10 million sperm. A 2001 study of 3,479 IUI cycles in 1,039 couples showed a pregnancy rate per cycle of only 2.5% in men with a TMC of less than 5 million, as opposed to 7.1% when the TMC was 5 million or greater. [Van Voorhis BJ. FertSteril 2001] Another study of 308 IUI cycles split couples into 3 groups based upon their TMC. For men with a TMC of less than 5 million, no successful pregnancies were reported with IUI. For men who had a TMC of 5 to 10 million, the pregnancy rate per cycle was 9.5%, and this rose to 17.4% when the TMC was above 10 million. [Cohlen BJ. HumReprod 1998]
Pre-Wash Total Progressive Count (TPMC)
Multiple studies have looked at TPMC counts pre-wash and their correlation with IUI outcomes. Some early studies recommended a pre-wash TPMCs of 1 million or above to increase the chances of a successful IUI. [Campana A. HumReprod 1996][Huang HY. JAssistReprodGenet 1996]. However, more recent studies suggest that a higher TPMC is associated with increases chances of pregnancy with IUI. A 2011 study looking at 820 IUI cycles in 445 couples found that pregnancy rates/cycle rose from 5.1% in men with a TMC < 5million to 15.1% in men with a TPMC that was between 5 and 10 million sperm. [Nikbakht R. IntJFertSteril 2011]. Similar results were found in a 2014 study of 672 IUI cycles where a pre-wash TPMC of <5 million sperm had a pregnancy rate of 0% as opposed to 12.73% in men with TPMC of between 5 to 10 million sperm. [Zhang E. MaterSociomed 2014].
Post-Wash Total Motile Counts (PWTMC)
The main problem with post-wash calculations is that these numbers are generally not available for new couples to counsel them on whether they would be good candidates for IUI. Also, there is evidence from studies showing that post-wash TMCs are no better at predicting IUI outcomes than pre-wash numbers. [Luco SM. EurJObstetGynReprodBiol 2014]. However, once a couple has done at least one IUI cycle, post-wash TMC numbers should be available for review and potentially provide additional information which can help guide couples in deciding on whether to try more cycles of IUI. A 2014 meta-analysis of 55 studies found that a PWTMC of 1 million sperm can be used as a cut-off for increased chance of success with IUI. {Ombulet W. ReprodBiomedOnline 2014]. However, a 2009 study of 393 couples found that if the PWTMC was < 5million sperm, then the pregnancy rate per cycle was 5.55%, as opposed to 24.28% if the PWTMC was 5 million or above. [Badawy A. FertSteril 2009].
Conclusion: It appears from the data that the total number of swimming sperm in the ejaculate do correlate with IUI outcomes. Both pre-wash and post-wash numbers can be used to predict the chances of success with IUI. Pre-wash numbers are more clinically useful for couples who have not yet tried IUI, but post-wash evaluations of semen parameters can help to predict the success of future cycles. There is significant controversy as to cut-off ranges for total numbers of swimming sperm below which a couple will be at a significantly increased risk of IUI failure and should just consider going straight to IVF. For pre-wash TMC, the general range is 5-10 million sperm and for pre-wash TPMC, this range falls between 1-5 million sperm. In terms of post-wash TMC, the range below which to consider moving on to IVF falls between 1-5 million sperm. One potential way to look at these numbers is that IUI is possible for couples that fall within these ranges, but to be a good “solid” candidate for IUI from the male side, you would ideally have a pre-wash TMC of 10 million or above, pre-wash TPMC of 5 million or above, or a post-wash TMC of 5 million or above.
IVF/ICSI
Not many sperm are needed for IVF/ICSI. The average women undergoing IVF typically has between 5-15 eggs retrieved, so theoretically only this number of viable sperm are needed to inject them. In the early days of ICSI, many clinicians felt that sperm quality no longer mattered because the ICSI process compensated for any defect in sperm quality (so long as enough viable sperm were present to inject each egg). However, many studies have now documented that lower sperm quality can have a negative impact on IVF/ICSI outcomes. Elevated levels of sperm DFI has been shown in a 2017 meta-analysis to negatively impact the outcomes of IVF/ICSI cycles. [Simon L. AsianJAndrol 2017]
Interestingly, a man’s total motile sperm count has also been shown to correlate with a couple’s chances of IVF/ICSI success as well. A 2016 study looking at 518 couples undergoing ICSI looked at the results of men who had a TPMC of < 1 million sperm vs. those with a TPMC of >20 million sperm. The group with a TPMC of >20 million sperm had a higher fertilization rate (84.9% vs. 72.5%) and lower miscarriage rate (17.9% vs. 33.3%) as opposed to men with a TPMC of <1million sperm. [Borges E. Andrology 2016]. Better TPMC’s also predicted the chances of having high quality embryos as well as the number of embryos that developed to the blastocyst stage. This provides further evidence that sperm quality should be optimized prior to a couple proceeding with treatments from the female side, including both IUI and IVF/ICSI.