By Dr. Grace Centola, Ph.D.
If you’re considering becoming a sperm donor or exploring donor sperm as part of your family-building journey, you’ve likely encountered the term “semen analysis.” While the report may look complicated with numbers, percentages, and medical terminology, understanding the basics can help you make informed decisions. After 40 years working in andrology—the study of diseases pertaining to the male reproductive system—I’ve learned that what seems straightforward on paper is actually quite fascinating and complex.
The Timeline You Should Understand
Here’s something that surprises most people – the sperm that ejaculated today was made 72 to 90 days ago in the testicle, and a lot has to happen before it can leave the testicle and do its work. This lengthy production timeline means that what we see in a semen analysis today reflects what was happening in a man’s body two to three months ago.
This is why when we get a donor sample that doesn’t look optimal, I often recommend patience. Illness, stress, or even lifestyle factors from weeks past could be impacting today’s results. It takes at least 12 days alone for sperm to mature enough to function properly, with the complete maturation process requiring 74 days.
Why Results Fluctuate
One of the most important things to understand about semen analysis is variability. There are significant fluctuations in sperm count and quality. So, a single sperm specimen or semen analysis may not be representative of the clinical status of the male.
In my lab, we’ve seen this countless times. A donor might show 19 million sperm per milliliter one day and a different count a few days later—and that’s completely normal. This is why in fertility medicine, doctors typically recommend at least three separate analyses, spaced three weeks apart, before making a final assessment.
However, for sperm donors, our approach is slightly different. These are generally men who are young and healthy, who are unlikely to do drugs or drink excessive amounts of alcohol. We know this because we’ve already interviewed them and we can usually make a good initial assessment from one comprehensive test. But if something seems off, we repeat the test.
Sperm’s Incredible Obstacle Course
To truly appreciate why a semen analysis matters, you need to understand what sperm must accomplish. I sometimes call it “Sparky Sperm’s Ironman Triathlon.” The journey begins with the first hurdle: cervical mucus. Interestingly, unless it’s right at the time or around a day or two around ovulation, the cervical mucus is not good for sperm, and the sperm won’t make it far.
Then comes what I call the “10K swim” from the cervical mucus into the uterus and up to the fallopian tubes. Here’s where it gets really challenging. The sperm don’t know which fallopian tube has the egg in it, so some will go one way, some will go the other.
And the fallopian tube itself? It’s not the smooth tube most people imagine. There are many wrinkles, little valleys and higher parts. And the egg, when it’s ovulated, may fall into one of those areas. All we can hope for is that at least one sperm figures out a way around the obstacles and finds its way to the egg.
After learning all this, I often tell people, “It’s amazing that anybody gets pregnant.” And here’s what’s truly remarkable – out of a million sperm, it’s a very small number that actually even get there. Less than a hundred sperm actually get into that little valley where the egg is.
What We Evaluate in Semen Analysis
When a sample arrives at the lab, we look at numerous factors:
Liquefaction: When semen is ejaculated, it’s really thick. When we first get it in the lab right after he collected, it’s like a gook. It’s just like a clump of stuff. The sample must liquefy at room temperature for at least 30 to 45 minutes before we can properly analyze it.
Color and Appearance: The semen should be whitish or gray and opaque. We don’t want it to be red or reddish because that would mean there’s blood in there. We don’t want it to be yellow, too yellow which could indicate urine contamination.
Volume: We want to see at least 1.5 milliliters, though more is preferable for donors. Volume affects everything because if you have a high volume, it dilutes the numbers of sperm.
Sperm Count: In 2021, the World Health Organization established 16 million sperm per milliliter as the minimum for fertility. For donors, we look for significantly higher numbers to account for losses during freezing.
Motility: This measures what percentage of sperm is moving. We want to see at least 30% of sperm demonstrating forward movement. But it’s not just about movement—it’s about how they move. Are they moving nice and fast or are they kind of just meandering along? We don’t want them to just meander along, they need to be strong and fast.
Progressive Movement: Sperm need to exhibit what we call “hyperactivated motion” when they near the egg. Instead of swimming in a straight line, they’re actually going around . By swimming all over the place, which helps them detect and penetrate the cumulus cells surrounding the egg.
Morphology: Using specialized staining techniques, we examine sperm shape under a microscope. We look for normally formed heads and properly structured tails. Under strict criteria, we want to see at least 4% normal forms. It’s not unusual to see curled or even bent tails, or a head that is long.
Other Factors: We also watch for white blood cells (which could indicate infection), clumping of sperm called agglutination, and viscosity issues. Viscosity means thick enough that the sperm have a difficult time swimming.
The Critical Importance of Proper Collection
How a sample is collected can make or break the analysis. I always emphasize proper collection protocols: The donor will be told to have an ejaculation, then abstain for three days or four, and then come in and give a sample. This timing is crucial because the longer the abstinence is the more dead sperm you will get.
Temperature control during transport is equally vital. At Coast to Coast, donors are sent a kit through our partner lab, and our team will walk through the instructions.
IVF or IUI – Understanding Frozen Sperm Samples
For recipients using frozen donor sperm, there’s one critical fact to understand – You will always lose up to 50% of the sperm by freezing and thawing. This is normal and expected, which is why post-thaw testing is so important.
For intrauterine insemination (IUI), most sperm banks guarantee at least 15 to 20 million motile sperm per vial after thawing. However, because we’re dealing with sperm donors, these are healthy young males, so we expect higher baseline counts.
For IVF, particularly with ICSI (intracytoplasmic sperm injection) where embryologists inject a single sperm directly into an egg, far fewer sperm are needed.
Why All This Matters
Over the last four decades, reproductive medicine has evolved, but one thing has become clear: semen analysis is both an art and a science. Selecting sperm for advanced procedures requires a highly experienced embryologist.
But even with all our knowledge and technology, reproduction retains an element of wonder. With the obstacle course that a sperm has to get through, it’s amazing that people get pregnant naturally! Yet that’s precisely why understanding semen analysis is so important—it helps us identify the best candidates for donation and guides recipients toward the most effective treatment options for their unique situations.
Whether you’re considering becoming a donor or choosing sperm donation to build your family, remember that these numbers and percentages represent possibility, hope, and the remarkable biological process that creates new.
Dr. Grace Centola, Ph.D., is a leading expert in reproductive tissue banking with decades of experience in sperm bank operations and donor screening protocols. Dr. Centola is the Tissue Bank Director of Coast to Coast Sperm Donation.
Medical Disclaimer: This article is for educational purposes only and does not constitute medical advice. Semen analysis results should always be interpreted by qualified healthcare professionals in the context of your specific situation. Individual results can vary, and what’s appropriate for one person or couple may differ for another. If you have questions about semen analysis, fertility treatment options, or donor selection, please consult with your physician or a reproductive endocrinologist.
