Asthenozoospermia is the medical term for a large percentage of sperm that do not swim straight forward quickly. A reduction in motility (movement) decreases the likelihood of sperm successfully swimming up the female reproductive tract in order to fertilize an egg.
According to the World Health Organization (WHO), asthenozoospermia occurs with less than 40% total motility (any movement in a semen sample) or 32% progressive motility (forward movement in a straight direction.)
An analysis of sperm motility during a semen analysis can provide insight into how sperm move, including their direction, speed, and endurance.
Asthenozoospermia may also be known as asthenospermia.
FertilitySmarts explains Asthenozoospermia
Sperm motility is one of the key components of male fertility. Ejaculated sperm need to be motile to penetrate cervical mucus, swim up the female reproductive tract, and penetrate the layers of the egg to fertilize the egg. Reduced motility or asthenozoospermia is involved in more than 40% of infertile men.
A sperm cell is composed of three parts, the head that holds the genetic material, mid-section, which provides the energy to power the last part, which is the flagellum or tail. The causes of asthenospermia include genetic abnormalities that prevent the cell from propelling the sperm or diseases that affect the structure of the sperm itself.
Causes of Asthenozoospermia
Causes of Asthenozoospermia include:
Excess testicular heat
While the vast majority of men with asthenospermia have some motile sperm, asthenospermia may be absolute, where all ejaculated sperm are immotile. Absolute asthenozoospermia is thought to occur in 1 in 5000 men.
Due to the fact that only the motility, and not the quality of the sperm affected, men with asthenozoospermia wishing to conceive may be candidates for in vitro fertilization (IVF) with a process called intracytoplasmic sperm injection (ICSI) in which an immotile sperm is directly inserted into an egg, allowing fertilization. The fertilized egg or zygote is then transferred back into the uterus.
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Ortega C, et al.
Absolute asthenozoospermia and ICSI: what are the options?.