Sperm count is only one part of the fertility picture. Sperm also need to swim well to reach and fertilise the egg. Asthenozoospermia is the medical term for reduced sperm motility, and it accounts for a significant portion of male infertility cases, either alone or in combination with other abnormalities.
What Is Asthenozoospermia?
According to WHO guidelines, at least 42% of sperm should show total motility (progressive plus non-progressive) and 30% should show progressive motility. When motility falls below these thresholds, it is classified as asthenozoospermia.
Causes of Poor Motility
- Varicocele and elevated scrotal temperature
- Genital tract infections such as prostatitis or epididymitis
- Anti-sperm antibodies
- Genetic conditions affecting sperm tail structure, such as Kartagener syndrome
- Oxidative stress from smoking, alcohol, obesity, or environmental toxins
- Prolonged abstinence or, conversely, very frequent ejaculation
- Hormonal imbalances and nutritional deficiencies (zinc, selenium, carnitine)
- Certain medications and chronic illnesses
Diagnosis
Diagnosis is confirmed by repeat semen analyses showing consistently low motility. Additional testing may include a sperm vitality test to distinguish live but immotile sperm from dead ones, sperm DNA fragmentation testing, hormone profile, scrotal ultrasound, and specialised tests for sperm antibodies or ultrastructural defects if indicated.
Treatment
- Lifestyle optimisation: Stop smoking, reduce alcohol, maintain a healthy BMI, avoid heat exposure, and manage stress.
- Antioxidants and supplements: L-carnitine, CoQ10, zinc, selenium, vitamin E, and folic acid have evidence for improving motility.
- Treat underlying causes: Antibiotics for infections, varicocele surgery, and hormonal correction when indicated.
- Assisted reproduction: IUI for mild cases when motility improves after preparation; IVF with ICSI for severe asthenozoospermia, which bypasses the need for sperm to swim to the egg.
What About Total Immotility?
Rarely, all sperm in the ejaculate are immotile. In such cases, sperm vitality testing and hypo-osmotic swelling tests help identify viable sperm for ICSI, and in some cases surgical retrieval from the testis may yield sperm with better motility.
Poor sperm motility can usually be managed effectively. A comprehensive evaluation by a reproductive medicine specialist can identify the underlying reason and guide the most suitable treatment.