Asthenozoospermia: what poor sperm motility means
Asthenozoospermia means your sperm count may be perfectly normal, but too few of them swim forward well enough to reach and fertilise an egg. Motility is often the parameter that responds fastest to treating the underlying cause.
How motility is measured
Labs report two numbers. Progressive motility is the percentage of sperm actively swimming forward in a straight line or large circles — the movement that actually matters for reaching an egg. Total motility adds in sperm that are moving but not going anywhere useful.
WHO 6th edition (2021) sets the reference thresholds at 30% progressive motility and 42% total motility. Asthenozoospermia is diagnosed below the progressive threshold. A related term, necrozoospermia, describes a sample where most sperm are not merely immobile but dead — vitality staining distinguishes the two.
Motility is the parameter most sensitive to sample handling. A sample that got cold in transit, sat too long before analysis, or touched a spermicidal lubricant will show artificially low motility. If your result is unexpectedly poor, ask how long the sample took to reach the microscope before concluding anything.
What causes it
Varicocele is again the most common correctable cause, and motility is often the first parameter to improve after repair. Infection or inflammation of the reproductive tract, including prostatitis, impairs movement and may be signalled by white blood cells in the sample.
Oxidative stress — an imbalance between free radicals and antioxidants in semen — damages the sperm midpiece where energy is produced, and is one of the better-established mechanisms behind poor motility. Smoking, obesity, and heat exposure all increase it.
Less commonly, motility problems are structural and lifelong: conditions such as primary ciliary dyskinesia affect the tail machinery itself. Anti-sperm antibodies, which make sperm clump together, are another distinct cause worth testing for when motility is low but count is normal.
What it means for conception, and what helps
Motility problems respond well to assisted reproduction because the techniques bypass the need for sperm to swim far. IUI concentrates the most motile sperm and places them directly in the uterus; ICSI removes the requirement entirely by injecting a single sperm into an egg. Even very low motility is compatible with ICSI as long as some sperm are alive.
For natural conception, the changes that help most are the ones that reduce oxidative stress: stopping smoking, avoiding scrotal heat, treating any infection, and repairing a varicocele where indicated. Antioxidant supplementation has its most consistent evidence for motility specifically, more so than for count.
As with count, judge results by a retest at three months. And use a fertility-friendly lubricant if you use one at all — most standard lubricants sharply reduce motility on contact.
FAQ
Can you conceive with low sperm motility?
Yes. Mild reductions in motility often still allow natural conception, sometimes taking longer. When motility is very low, IUI or IVF with ICSI is highly effective because these techniques do not require sperm to swim to the egg. What matters most is whether the sperm are alive, not whether they are fast.
What is a good progressive motility percentage?
WHO 6th edition sets the reference threshold at 30% progressive motility, with 42% total motility. Higher is better, and many fertile men are well above these numbers. As with all semen parameters, these thresholds represent the 5th percentile of men whose partners conceived within a year, not a pass/fail line.
How can I improve sperm motility?
Stop smoking, avoid hot tubs and saunas, treat any reproductive tract infection, lose weight if overweight, and have a varicocele evaluated. Antioxidant supplements such as CoQ10 have their strongest evidence for motility. Allow three months before retesting, since sperm take about 74 days to develop.
Why was my motility so much worse than last time?
Motility is the parameter most affected by how the sample was handled. Delay between collection and analysis, exposure to cold, and contact with lubricant all lower it artificially. Illness or fever in the preceding three months also has a real effect. A single poor motility result should be confirmed with a repeat test.