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Also known as
Asthenospermia, poor sperm motility, reduced sperm motility, low sperm motility
Definition
Asthenozoospermia, also referred to as asthenospermia, is a medical condition characterized by reduced sperm motility, meaning the sperm have a diminished ability to move or swim effectively. ¹˒² Specifically, it is diagnosed when less than 32% of spermatozoa exhibit progressive motility (i.e., active movement, either linearly or in a large circle, regardless of speed) or when less than 40% of sperm show total motility (progressive and non-progressive).³ This impaired motility significantly hinders the sperm’s capacity to travel through the female reproductive tract, reach the egg, and achieve fertilization, thereby constituting a common factor in male infertility. ¹˒⁴ Absolute asthenozoospermia is a severe form where no sperm exhibit any movement, although they may still be viable.³ The condition can arise from a multitude of factors, including genetic abnormalities, infections, varicocele, lifestyle factors, or exposure to detrimental substances.¹ The underlying mechanisms can involve defects in the sperm flagellum structure, energy production pathways, or the biochemical environment of the semen.⁴
Clinical Context
Asthenozoospermia is a significant clinical finding in the evaluation of male infertility, as sperm motility is a crucial factor for natural conception. It is typically identified during a semen analysis, which is a cornerstone investigation for couples experiencing difficulty conceiving.¹˒² Clinically, asthenozoospermia may be suspected in men with a history of urogenital infections, varicocele, testicular torsion, exposure to gonadotoxins (e.g., certain medications, radiation, chemotherapy, environmental toxins), or lifestyle factors such as smoking, excessive alcohol consumption, and obesity.¹ Genetic factors, including chromosomal abnormalities and specific gene mutations affecting sperm structure or function (e.g., primary ciliary dyskinesia, mitochondrial dysfunction), can also lead to asthenozoospermia.¹
The clinical management of asthenozoospermia depends on the underlying cause and severity. If a reversible cause is identified, such as an infection or varicocele, treating the primary condition may improve sperm motility. Lifestyle modifications, including dietary changes, exercise, and cessation of smoking or excessive alcohol intake, are often recommended.¹ Antioxidant supplementation has also been explored, though evidence for its efficacy can be varied.¹
For cases where conservative measures are insufficient or no reversible cause is found, assisted reproductive technologies (ART) are often the most effective treatment options. Intrauterine insemination (IUI) may be considered for mild to moderate asthenozoospermia, where processed sperm with better motility are directly placed into the uterus. However, for more severe asthenozoospermia, or if IUI fails, in vitro fertilization (IVF) with intracytoplasmic sperm injection (ICSI) is commonly employed. ICSI bypasses the need for sperm to actively swim to and penetrate the egg, as a single sperm is directly injected into each mature egg.¹ The expected outcomes with ART depend on various factors, including female partner’s age and fertility status, as well as the overall sperm quality beyond just motility. Even with absolute asthenozoospermia (100% immotile sperm), viable sperm can sometimes be retrieved and used for ICSI, potentially leading to successful pregnancy.²
Patient selection for specific treatments involves a comprehensive fertility evaluation of both partners. This includes a detailed medical history, physical examination, repeated semen analyses, hormonal profiling, and potentially genetic testing or testicular biopsy in select cases.¹ The expected outcomes are discussed with the couple, considering the chances of success with different approaches and the associated physical, emotional, and financial implications.