Definition - What does Non-Motile Sperm mean?
Non-motile sperm are sperm cells that are unable to move. Non-motile sperm cannot rhythmically swing the tail to move in a forward direction due to a structural or functional defect of the sperm.
Sperm need to travel a long distance from the vagina to the fallopian tubes to fertilize the egg. Of the millions of sperm that are released into the vagina during ejaculation, only a few survive this journey. The ability to maintain progressive forward movement through the reproductive tract is key to successful fertilization.
Semen with more than 60% non-motile sperm decreases the chances of successful fertilization of the egg and is a known cause of male factor infertility.
FertilitySmarts explains Non-Motile Sperm
The tail of the sperm is the most important structure for determining sperm motility. The tail motion requires a lot of energy, which is supplied by the sperm’s mitochondria. The mitochondria help produce ATP, which is the basic source of energy in cells. Structural, functional or metabolic abnormalities of the sperm can impair sperm mobility.
Sperm can be classified into 5 groups based on their motility:
- Grade 0: Non-motile sperm. No motion at all.
- Grade 1: Some motion of sperm is present, but there is no forward movement.
- Grade 2: Sperm movement is slow and does not move in a straight line.
- Grade 3: Sperm can move forward but the speed is slow or it cannot move in a straight line.
- Grade 4: Sperm can move forward at a steady speed in a straight line.
What causes non-motile sperm?
Some of the common causes of non-motile sperm include:
- Abnormalities of the male reproductive tract
- Genetic diseases (eg: cystic fibrosis)
- Sperm DNA abnormalities
- Exposure to chemicals (eg: chemotherapy) and toxins (eg: heavy metals)
- Environmental factors (eg: exposure of testicles to extreme heat, cold or radiation)
Sperm cells go through many cycles of cell division and maturation to achieve their final form and function. They gain full motility late in development after entering the epidermis.
When sperm is retrieved surgically from the testicles, there is an increased chance of collecting immature sperm that are either non-motile or weakly motile. But studies have shown that sperm motility does not have a significant impact on the success rates of assisted reproductive technologies such as in vitro fertilization (IVF) with Intracytoplasmic sperm injection (ICSI). That's because the sperm is injected into the egg, and therefore does not need to be motile to reach the egg.
- The motility of epididymal or testicular spermatozoa does not directly affect IVF/ICSI pregnancy outcomes. (2005).